Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Effect of Previous Crop Roots on Soil Compaction in 2 Yr Rotations under a No-Tillage System

Effect of Previous Crop Roots on Soil Compaction in 2 Yr Rotations under a No-Tillage System land Article Effect of Previous Crop Roots on Soil Compaction in 2 Yr Rotations under a No-Tillage System Jay D. Jabro *, Brett L. Allen, Tatyana Rand, Sadikshya R. Dangi and Joshua W. Campbell Northern Plains Agricultural Research Laboratory, ARS-USDA, 1500 N Central Avenue, Sidney, MT 59270, USA; brett.allen@usda.gov (B.L.A.); Tatyana.Rand@usda.gov (T.R.); Sadikshya.Dangi@usda.gov (S.R.D.); Joshua.campbell@usda.gov (J.W.C.) * Correspondence: jay.jabro@usda.gov; Tel.: +1-406-433-9442 Abstract: Compacted soils affect global crop productivity and environmental quality. A field study was conducted from 2014 to 2020 in the northern Great Plains, USA, to evaluate the effect of various rooting systems on soil compaction in 2 yr rotations of camelina (Camelina sativa L.), carinata (Brassica carinata A.) and a cover crop mix planted in place of fallow with durum (Triticum durum D.). The study was designed as a randomized complete block with three replications in a no-tillage system. The soil was classified as Dooley sandy loam (fine-loamy, mixed, superactive, frigid Typic Argiustolls) derived from glacial till parent material. Three measurements of soil penetration resistance (PR) were taken with a penetrometer to a depth of 0–30 cm within each plot. Soil moisture contents were determined using a TDR sensor at the time of PR measurements. Both measurements were monitored prior to planting in spring and after harvest. Initial PR results from spring 2014 showed that all plots had an average of 2.244 MPa between the 8–20 cm depth, due to a history of tillage and wheel traffic caused by various field activities. Covariance analysis indicated that soil PR was not significantly affected by crop type and moisture content. After one cycle of the 2 yr rotation, the Citation: Jabro, J.D.; Allen, B.L.; 2016 measurements indicated that the compacted layer existed at the same initial depths. However, Rand, T.; Dangi, S.R.; Campbell, J.W. after two and three cycles, soil PR values were reduced to 1.480, 1.812, 1.775, 1.645 MPa in spring Effect of Previous Crop Roots on Soil 2018 and 1.568, 1.581, 1.476, 1.458 MPa in 2020 under camelina, carinata, cover crop mix, and durum Compaction in 2 Yr Rotations under a treatments, respectively. These findings indicate that previous cover crop roots could effectively No-Tillage System. Land 2021, 10, 202. improve soil compaction by penetrating the compacted layer, decompose over time and form voids https://doi.org/10.3390/ and root channels. Although these results are novel and significant, further research is needed on land10020202 different soils and under cover crops with different root systems to support our findings prior to making any conclusion. Academic Editors: Richard Cruse and Teodor Rusu Keywords: soil compaction; penetration resistance; biological method; root channels; bio-pores Received: 23 December 2020 Accepted: 12 February 2021 Published: 17 February 2021 1. Introduction Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in Soil compaction is a form of degradation affecting future global food security and published maps and institutional affil- continues to be a problem for farmers in many parts of the world [1]. Over the past iations. few decades, management practices and field activities as well as wheel traffic from various heavy farm machinery have led to an increase in soil compaction, prompting global concerns on soil quality, hydrological properties, and crop production [2–6]. It can significantly reduce total soil porosity, change pore size distribution, affect hydrological Copyright: © 2021 by the authors. processes, and impact crop production for food security [1–3,5–8]. Licensee MDPI, Basel, Switzerland. Several approaches have been utilized to alleviate soil compaction in agricultural This article is an open access article lands including mechanical, natural, and biological. Mechanical methods such as deep distributed under the terms and tillage or subsoiling are good practical solutions in alleviating compaction problems in conditions of the Creative Commons subsurface soil layers; however, these processes have detrimental effects on soil quality Attribution (CC BY) license (https:// and organic matter decomposition as well as involving considerable expenditures of time, creativecommons.org/licenses/by/ money and fuel [2,9–11]. 4.0/). Land 2021, 10, 202. https://doi.org/10.3390/land10020202 https://www.mdpi.com/journal/land Land 2021, 10, 202 2 of 10 Natural repeated freezing and thawing cycles and their dynamic forces have been proven effective tools for lessening soil compaction and improving soil physical quality in the top layers over winter periods in cold regions [3,12]. Biological methods such as deep-rooted cover crops can be another potential solution to ameliorate the negative effects of soil compaction, particularly in no-tillage farming production [11,13,14]. Cover crops (e.g., radish, safflower, turnip, etc.) with vigorous taproots can reduce soil compaction by penetrating and loosening the compacted layer. Eventually, these roots decompose over time and form root channels and large voids that enable air, water, nutrient and roots of subsequent crops to move more deeply through the soil profile, thus enhancing soil macropores and physical quality [15,16]. Some researches refer to this biological process as a “bio-drilling” or “biological drilling” or “bio-tillage” which is the root-induced formation of voids “bio-pores” that present deep paths for air, water, nutrient movement, and root growth, and penetration of subsequent crops [15–18]. Ehlers et al. [17] evaluated soil penetration resistance and root growth of oats in tilled and untilled soils. They concluded that root channels or “bio-pores” created by roots of preceding crops acted as passages for subsequent crops in the soil profile in no-tillage systems. Williams and Weil [15] observed that soybean roots grew through the compacted plow pan soil using channels and “bio-pores” created by decomposition of cover crop roots. Similarly, Chen and Weil [16] evaluated the effect of three cover crop roots in compacted soils. They concluded that forage radish and rapeseed had at least twice as many roots as rye in a highly compacted soil and determined that tap-rooted crops may penetrate the compacted soil layer far better than fibrous-rooted crops. Recently, Rosolem and Pivetta [11] investigated both mechanical and biological meth- ods to alleviate soil compaction in tropical clay soils. In their study, they evaluated root growth and activity of soybean and maize grown in rotation with cover crops. They found that including ruzi grass and castor cover crops in the rotation increased root growth, activity and “bio-pores” in the soil profile as well as increased soybean yield. We hypothesized that cover crops and cool-season oilseed crops with different root systems (i.e., vigorous taproots, fibrous roots) would have a potential to alleviate soil compaction in agricultural lands. Globally, soil compaction can affect crop productivity and millions of hectares are affected by soil compaction that cost farmers millions of dollars every year. Crop roots can improve compacted soils and eliminate the need for expensive tillage operations, which tend to provide only a short-term benefit while reversing benefits of no-till production on soil quality. Further, information about using crop roots as an approach to biologically managing and loosening compacted soils in the MonDak region (eastern Montana and western North Dakota, USA) of the northern Great Plains is lacking. Therefore, the objective of this study was to evaluate the effect of previous crop roots on soil compaction in 2 yr durum wheat rotations with camelina, carinata and a cover crop mix planted in place of fallow in a no-tillage farming system. 2. Materials and Methods 2.1. Field Experiment A long-term field study was carried out from 2014 to 2020 at the USDA-ARS dryland 0  0 site located approximately 11 km north of Culbertson (48 33 N, 104 50 W, altitude 589 m) in the northern Great Plains, USA. The soil at the research site was classified as Dooley sandy loam (fine-loamy, mixed, superactive, frigid Typic Argiustolls) (https://soilseries.sc. egov.usda.gov (accessed on 16 February 2021)), derived from glacial till parent material, with a slope of 0 to 2%. The amounts of sand, silt, and clay in Ap horizon (0–15 cm) were approximately 62%, 22%, and 16%, respectively, and in Bt (15–30 cm) horizon were approximately 60%, 21%, and 19%, respectively. The presence of argillic horizon in this layer can greatly restrict water flow, root development and has higher density values and less macropores. The soil sampled prior to initiation of this experiment contained Land 2021, 10, 202 3 of 10 approximately 1.7% organic matter and has 7.2 pH at the 0–20 cm depth [19]. Monthly precipitation amounts during 2014–2020 growing seasons at the study site are given in Table 1. The previous cropping system was continuous spring or spring wheat–summer fallow at this site for over 30 years. Annual tillage to a depth of 15 to 20 cm was typical prior to 2005 to control weeds and prepare the seedbed for planting. Thereafter, no-tillage was practiced and weeds were controlled with herbicides. The moldboard plow has not been used at this field for over 25 years. Table 1. Monthly precipitation from April to September during 2014–2020 growing seasons at the research site near Culbertson, MT, USA. Precipitation, mm Average Month 2014 2015 2016 2017 2018 2019 2020 April 30.5 5.1 47.8 4.6 35.3 34.5 6.1 23.4 May 39.9 32.3 51.8 7.9 62.0 31.0 45.5 38.6 June 62.5 82.3 101.1 12.2 55.9 75.9 46.7 62.4 July 25.1 42.9 63.2 34.3 76.2 46.5 73.7 51.7 August 70.6 44.7 4.1 45.7 14.7 124.5 1.2 43.6 September 18.3 33.0 78.5 47.5 51.1 169.7 0 56.9 Total 246.9 240.3 346.5 152.2 294.2 482.1 173.2 276.5 Crops in a 2 yr rotation with durum wheat (Triticum durum D.) were camelina (Camelina sativa L.), carinata (Brassica carinata A.), both belonging to the Brassicace family, and a cover crop mix (10 species). The cover crop mix was composed of 12% lentil (Lens culinaris), 19% forage pea (Pisum sativum), 6% radish (Raphanus sativus), 3% turnip (Brassica rapa subsp), 3% winter canola (Brassica napus), 6% flax (Linum usitatissimum), 13% forage sorghum (Sorghum vulgare Pers), 6% German millet (Setaria italic), 19% cowpea (Vigna unguiculata), and 13% buckwheat (Fagopyrum esculentum). We planted a diversified cover crop mix to maximize ecosystem services with inclusion of functional groups including pollinator species, warm and cool season plants, broadleafs and grasses, legumes, and crucifer species. A highly variable climate in the region typically favors different species productivity among years, hence the desire to plant a highly diversified cover crop mix. Planting for all crops in the study took place in late April to early May using a custom built no-till research drill with double-shoot Barton single-disk openers on 20.3 cm row spacing. Durum “Grenora” was planted at 67 kg ha . Camelina “Suneson”, carinata “A110”, and the cover crop mix were planted at 9.0, 7.3, and 26.9 kg ha . Crop seeds were harvested with a Kincaid 8XP research combine (manufactured in Haven, KS, USA). Camelina seed was typically harvested late July to early August; durum harvest was early to mid-August. Carinata seed was harvested late August to mid-September. The cover crop mix was swathed for forage at pea bloom, typically occurring in mid-July. Following forage harvest, the cover crop was allowed to regrow unharvested and was terminated each year with a killing frost that typically occurred late September to mid-October. Fertilizer was banded at planting 5 cm below and 5 cm to the side of seed. Urea (45-0-0) was applied to durum, camelina, and carinata based on yield goals of 2350, 1800, 1 1 and 1800 kg ha , resulting in N application rates of 129, 90, and 117 kg ha , respectively, according to fertilizer guidelines for Montana crops [20]. Urea rates were adjusted by subtracting N from monoammonium phosphate and ammonium sulfate fertilizer and from residual soil nitrate that was determined from soil samples (0–60 cm depth) taken the previous fall. All plots received 56 and 45 kg ha monoammonium phosphate (11-52-0) and potassium chloride (0-0-60) and camelina and carinata plots received 112 kg ha ammonium sulfate (20-0-0-24) banded at planting. Weed control consisted of preplant and post-harvest applications of glyphosate her- –1 –1 bicide at 3.36 kg a.i. ha . Durum also received an in-crop application of 0.68 kg a.i. ha –1 bromoxynil and 0.09 kg a.i ha fenoxaprop herbicides. Camelina and carinata received –1 9.0 kg a.i. ha ethylfluralin in late fall preceding spring planting. Land 2021, 10, 202 4 of 10 Research plots in the rotation were arranged in randomized complete block design with three replications. Each crop phase of the rotation was present in every year for a total of 18 plots from three different rotations. Each plot measured 6 m wide  15 m long. 2.2. Field Measurements Soil penetration resistance (PR) was measured using a hand-held digital stainless steel cone-tipped penetrometer (12.8 mm diameter, 30 cone) (Field Scout, SC 900 Soil Compaction Meter; Spectrum Technologies, Inc., Plainfield, IL, USA). Measurements were made at three locations on a diagonal transect across each plot, one at the middle of the plot and the other two at each end of the plot. Penetration resistance readings (MPa) were recorded to the 30 cm depth at intervals of 2.5 cm [3,19]. At the time of PR measurements, soil moisture contents were determined for each plot using a digital TDR at three measurements per plot adjacent to PR positions (Field Scout, TDR 300 Soil Moisture Meter; Spectrum Technologies, Inc., Plainfield, IL, USA. Soil PR and volumetric moisture content were monitored shortly after planting and after harvest in each plot every year throughout the course of the study. Measurements were taken on 13 May, 11 September in 2014; 30 April, 11 September in 2015; 2 May, 26 September in 2016; 5 May, 4 October in 2017; 3 May, 2 October in 2018; 8 May, 8 October in 2019; and 21 April in 2020. 2.3. Statistical Analysis The mixed model of SAS was used for data analysis [21] using repeated measures over time as randomized block model with previous crop as a fixed effect, and year and replication as random effects. The variables PR and volumetric moisture content measured by the TDR were tested for linearity and a significant linear correlation was found between these two soil parame- ters (r = 0.254, p = 0.009). Therefore, analysis of covariance was used to analyze soil PR for the compacted layer of 8–20 cm depth using moisture content as a covariable parameter. Mean separation utilized least significant differences at p  0.05. 3. Results and Discussion Statistical results from analysis of covariance indicated that soil PR varied significantly by year (p < 0.0001) and not significantly by previous crop (p = 0.0554), with a significant interaction for previous crop  year (p = 0.0014). Results indicated that the effect of previous crop on soil moisture content was not significant in all six years (Table 2). Table 2. Mean values of volumetric moisture content (%) across 0–20 cm depth as affected by previous crop (spring measurements) in the compacted layer (8–20 cm) for 2015–2020 growing seasons. Volumetric Moisture Content, % Previous Crop 2015 2016 2017 2018 2019 2020 Camelina 21.18 20.61 19.52 20.78 20.71 19.47 Carinata 22.57 19.67 19.87 21.28 20.99 20.06 Cover crop mix 20.36 20.26 19.51 21.06 20.29 20.05 Durum 20.67 21.19 19.51 20.82 20.20 20.10 The effects of previous crop on soil PR and volumetric moisture content in the com- pacted layer of 8–20 cm for the 2015, 2016, 2017, 2018, 2019, and 2020 growing seasons are presented in Table 3. The effect of previous crop on soil PR was not significant in all years except in 2015 and 2017. Variations in the PR among crops in 2015 and 2017 may be related to the soil variability within the field (Table 3). Land 2021, 10, 202 5 of 10 Table 3. Analysis of covariance results showing the effect of previous crop on mean soil penetration resistance (spring measurements) of the compacted layer (8–20 cm) for the 2015–2020 growing seasons. Penetration Resistance, MPa Previous Crop 2015 2016 2017 2018 2019 2020 Camelina 2.503a 2.112a 2.930ab 1.480b 1.863a 1.568a Carinata 2.600a 2.475a 2.707a 1.812a 2.115a 1.581a Cover crop mix 2.252ab 2.563a 3.134b 1.775a 1.949a 1.476a Durum 2.027b 2.328a 2.698a 1.645a 2.175a 1.458a Analysis of covariance Effect p > F Previous crop 0.0211 0.0986 0.0303 0.1245 0.1731 0.2293 Moisture 0.0882 0.8208 0.5205 0.6274 0.0963 0.8019 content In 2014, average soil penetration resistance for the compacted layer (8–20 cm) was 2.244 MPa where durum was a previous crop in all plots. Numbers followed by different lowercase letters within a column in a set are significantly different at p = 0.05. In 2014, soil PR averaged across all 18 plots was 2.244 MPa where durum or spring wheat was a previous crop for over 30 years. Results from 2014 showed all plots had a compacted layer that exceeded the critical compaction level of 2 MPa between the 8–20 cm depth [22], presumably due to a history of tillage that likely caused a plow pan layer, Land 2021, 10, x FOR PEER REVIEW 6 of 10 presence of argillic horizon, continuous monocropping of spring wheat, and wheel traffic caused by other farming activities and management practices (Figure 1). Penetration resistance, MPa 0.00.5 1.01.5 2.02.5 3.0 All plots 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Figure 1. Initial mean soil penetration resistance across all plots in 2014, and across camelina, carinata, Figure 1. Initial mean soil penetration resistance across all plots in 2014, and across camelina, cari- cover crop mix, and durum after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in 2020. nata, cover crop mix, and durum after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in Average soil penetration resistance across camelina, carinata, cover crop mix, and du- rum plots for the 8–20 cm layer after one, two, and three cycles of the 2 yr rotation were Similarly, soil PR from 0 to 30 cm depth under camelina, carinata, cover crop mix, 2.370, 1.678, and 1.521 MPa in 2016, 2018, and 2020, respectively. and durum are presented in Figures 2–5, respectively. Soil penetration resistance for the After one cycle of the 2 yr rotation (2014–2016), soil PR measured in spring 2016 indicated compacted layer under these crops exhibited similar patterns as described in Figure 1. that the compacted layer continued to exist at the same depth of 8–20 cm. After two cycles (2014–2018), soil PR measurements in spring 2018 indicated that the compacted layer was Penetration resistance, MPa 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Camelina 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Figure 2. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in 2020 for camelina as a previous crop. Depth, cm Depth, cm Land 2021, 10, x FOR PEER REVIEW 6 of 10 Penetration resistance, MPa 0.00.5 1.01.5 2.02.5 3.0 All plots 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Land 2021, 10, 202 6 of 10 Figure 1. Initial mean soil penetration resistance across all plots in 2014, and across camelina, cari- decreased below the critical level of 2 MPa by 25.2% regardless of the rooting characteristics nata, cover crop mix, and durum after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in of the rotation crops. After three cycles (2014–2020), soil PR measurements in spring 2020 indicated that the compacted layer was reduced once again by 32.2% (Figure 1). Similarly, soil PR from 0 to 30 cm depth under camelina, carinata, cover crop mix, Similarly, soil PR from 0 to 30 cm depth under camelina, carinata, cover crop mix, and and durum durum ar are presented e presented in in Figu Figures res 2–5, respecti 2–5, respectively vely. Soi . Soil l penetration penetration resista resistance nce f for or the the compacted layer under these crops exhibited similar patterns as described in Figure 1. compacted layer under these crops exhibited similar patterns as described in Figure 1. Penetration resistance, MPa 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Camelina 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Land 2021, 10, x FOR PEER REVIEW 7 of 10 Figure 2. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, Figure 2. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in 2020 for camelina as a previous crop. after 2 cycles in 2018, and after 3 cycles in 2020 for camelina as a previous crop. Penetration resistance, MPa 0.00.5 1.01.5 2.02.5 3.0 Carinata 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Figure 3. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, Figure 3. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in 2020 for carinata as a previous crop. after 2 cycles in 2018, and after 3 cycles in 2020 for carinata as a previous crop. Penetration resistance, MPa 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Cover crop mix 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Figure 4. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in 2020 for cover crop mix as a previous crop. Depth, cm Depth, cm Depth, cm Depth, cm Land 2021, 10, x FOR PEER REVIEW 7 of 10 Penetration resistance, MPa 0.00.5 1.01.5 2.02.5 3.0 Carinata 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Land 2021, 10, 202 7 of 10 Figure 3. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in 2020 for carinata as a previous crop. Penetration resistance, MPa 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Cover crop mix 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Land 2021, 10, x FOR PEER REVIEW 8 of 10 Figure 4. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, Figure 4. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in 2020 for cover crop mix as a previous crop. after 2 cycles in 2018, and after 3 cycles in 2020 for cover crop mix as a previous crop. Penetration resistance, MPa 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Durum 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Figure 5. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, Figure 5. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in 2020 for durum as a previous crop. after 2 cycles in 2018, and after 3 cycles in 2020 for durum as a previous crop. After one cycle of the 2 yr rotation (2014–2016), soil PR measured in spring 2016 under After one cycle of the 2 yr rotation (2014–2016), soil PR measured in spring 2016 un- camelina, carinata, cover crop mix, and durum indicated that the compacted layer was der camelina, carinata, cover crop mix, and durum indicated that the compacted layer was present at the 8–20 cm depth. After two and three cycles, soil PR in the compacted layer present at the 8–20 cm depth. After two and three cycles, soil PR in the compacted layer was decreased below the threshold of 2 MPa under each crop. Reductions in soil PR in was decreased below the threshold of 2 MPa under each crop. Reductions in soil PR in the the compacted layer after two and three cycles under camelina, carinata, cover crop mix, compacted layer after two and three cycles under camelina, carinata, cover crop mix, and and durum are given in Table 4. These reductions ranged between 19.3–34% and 29.5–35% durum are given in Table 4. These reductions ranged between 19.3–34% and 29.5–35% after two and three cycles, respectively. after two and three cycles, respectively. Table 4. Reduction in soil penetration resistance in the compacted layer (8–20 cm) for durations 2014–2018 and 2014–2020 under camelina, carinata, cover crop mix, and durum. Reduction in Soil Penetration Resistance, % Previous Crop 2014–2018 2014–2020 Camelina 34.0 30.1 Carinata 19.3 29.5 Cover crop mix 20.9 34.2 Durum 26.7 35.0 All plots (average) 25.2 32.2 The root systems of cover crop mix and durum tended to have greater effects in loos- ening the compacted soil by creating more root channels and voids than both camelina and carinata after three cycles of the rotation (Table 4). The cover crop mix treatment had various crops with a vigorous taproot system such as radish, forage sorghum, and turnip that penetrated through the compacted soil layer, decomposed over time, and created voids and passages through the dense layer. Concluding results indicated that root systems of cover crops used in this study re- quired approximately four years to be decomposed and produced root channels and pore spaces in the compacted soil profile. These findings showed that roots of camelina, cari- nata, cover crop mix, and durum could have a potential to decrease soil penetration re- Depth, cm Depth, cm Depth, cm Land 2021, 10, 202 8 of 10 Table 4. Reduction in soil penetration resistance in the compacted layer (8–20 cm) for durations 2014–2018 and 2014–2020 under camelina, carinata, cover crop mix, and durum. Reduction in Soil Penetration Resistance, % Previous Crop 2014–2018 2014–2020 Camelina 34.0 30.1 Carinata 19.3 29.5 Cover crop mix 20.9 34.2 Durum 26.7 35.0 All plots (average) 25.2 32.2 The root systems of cover crop mix and durum tended to have greater effects in loosening the compacted soil by creating more root channels and voids than both camelina and carinata after three cycles of the rotation (Table 4). The cover crop mix treatment had various crops with a vigorous taproot system such as radish, forage sorghum, and turnip that penetrated through the compacted soil layer, decomposed over time, and created voids and passages through the dense layer. Concluding results indicated that root systems of cover crops used in this study Land 2021, 10, x FOR PEER REVIEW 9 of 10 required approximately four years to be decomposed and produced root channels and pore spaces in the compacted soil profile. These findings showed that roots of camelina, carinata, cover crop mix, and durum could have a potential to decrease soil penetration resistance in sistance in the compacted layer by penetrating the compacted layer, eventually decom- the compacted layer by penetrating the compacted layer, eventually decompose, and form pose, and form biological voids and channels, which enable air, water, nutrient and root biological voids and channels, which enable air, water, nutrient and root growth for following crops growt to move h for easily follow thr ing crop ough the s to compacted move easily through the compa layer. cted layer. Figure 6 shows roots for various crops (sorghum, radish, turnip, etc.) in the cover Figure 6 shows roots for various crops (sorghum, radish, turnip, etc.) in the cover crop mix treatment crop mi growing x trea andtpenetrating ment growin thr g a ough nd penetrati the compacted ng through t soil h layer e compa in summer cted soil la of yer in summer 2017. These roots of 2017. These roots will d will decompose over time eco and mpose ov form lar er time ge voids and and form large vo root channels ids in and the root channels in compacted layer. the compacted layer. Figure 6. An image showing roots for (A) sorghum and (B) turnip through dense soil layers in the Figure 6. An image showing roots for (A) sorghum and (B) turnip through dense soil layers in the cover crop mix treat- ment. cover crop mix treatment. The decomposition rate of cover crop roots and plant residues primarily depends on The decomposition rate of cover crop roots and plant residues primarily depends on many factors including soil aeration, moisture content, temperature, texture, acidity, tillage, many factors including soil aeration, moisture content, temperature, texture, acidity, till- crop species, nitrogen availability, plant characteristics as well as microbial diversity and age, crop species, nitrogen availability, plant characteristics as well as microbial diversity activities in the soil [23]. and activities in the soil [23]. The results of the study confirm previous research that showed that tap-rooted crops The results of the study confirm previous research that showed that tap-rooted crops are more effective than fibrous-rooted crops in ameliorating compacted soils [16,18,24]. are more effective than fibrous-rooted crops in ameliorating compacted soils [16,18,24]. Nevertheless, further investigations on different textured soils with various tap-rooted Nevertheless, further investigations on different textured soils with various tap-rooted crops (i.e., rye grass, radish, safflower, turnip, Lucerne or alfalfa, rape, sugarbeet, chicory, crops (i.e., rye grass, radish, safflower, turnip, Lucerne or alfalfa, rape, sugarbeet, chicory, etc.) as well as cover crops with fibrous-rooted crops are required for conclusive recom- mendations on crop rotations to avoid/recover from soil compaction in a no-tillage sys- tem. 4. Conclusions Overall, after two cycles of the 2 yr rotation, soil PR measurements in 2018 indicated that the compacted layer was decreased below the threshold of 2 MPa, by 25.2% (1.706 MPa) in sandy loam soil. After three cycles, PR measurements in 2020 indicated that the compacted layer was reduced once again by 32.2% (1.480 MPa). These findings indicate that previous crop roots could effectively decrease soil compaction. Results indicated that crop roots required approximately 4–6 years to decompose and produce root channels and bio-voids through the soil compacted layer. Our results showed that decayed cover crop roots over time could combat soil compaction. More re- search is needed to confirm these results on different soils and using various deep-rooted crops with vigorous taproots as well as cover crops with fibrous roots prior to making any explicit conclusion. Roots of cover crop species may differ in their ability to grow and penetrate the compacted soil layers as well as in their decomposition rates in different soils and under various environments. Author Contributions: Conceptualization, J.D.J., and B.L.A.; methodology, J.D.J. and B.L.A.; writ- ing—original draft preparation, J.D.J.; statistics, J.D.J.; writing—review and editing, J.D.J., and Land 2021, 10, 202 9 of 10 etc.) as well as cover crops with fibrous-rooted crops are required for conclusive recom- mendations on crop rotations to avoid/recover from soil compaction in a no-tillage system. 4. Conclusions Overall, after two cycles of the 2 yr rotation, soil PR measurements in 2018 indicated that the compacted layer was decreased below the threshold of 2 MPa, by 25.2% (1.706 MPa) in sandy loam soil. After three cycles, PR measurements in 2020 indicated that the com- pacted layer was reduced once again by 32.2% (1.480 MPa). These findings indicate that previous crop roots could effectively decrease soil compaction. Results indicated that crop roots required approximately 4–6 years to decompose and produce root channels and bio-voids through the soil compacted layer. Our results showed that decayed cover crop roots over time could combat soil compaction. More research is needed to confirm these results on different soils and using various deep-rooted crops with vigorous taproots as well as cover crops with fibrous roots prior to making any explicit conclusion. Roots of cover crop species may differ in their ability to grow and penetrate the compacted soil layers as well as in their decomposition rates in different soils and under various environments. Author Contributions: Conceptualization, J.D.J., and B.L.A.; methodology, J.D.J. and B.L.A.; writing— original draft preparation, J.D.J.; statistics, J.D.J.; writing—review and editing, J.D.J., and B.L.A.; visualization, J.D.J.; funding acquisition, B.L.A.;investigation, J.D.J., B.L.A., T.R., S.R.D., and J.W.C.; project administration, J.D.J., B.L.A., T.R., S.R.D., and J.W.C; review and editing, T.R., S.R.D., and J.W.C. All authors have read and agreed to the published version of the manuscript. Funding: This research was supported by Agrisoma Biosciences Inc., 200, Rue Montcalm, Suite 300 Gatineau, Quebec J8Y 3B5. Data Availability Statement: Data have already been provided within the manuscript. However, other relevant data or information can be requested from the authors. Acknowledgments: We acknowledge the help of Dale Spracklin with soil measurements during the course of this study. Conflicts of Interest: The authors declare no conflict of interest. Disclaimer: Mention of trade names, proprietary products, or specific equipment is intended for reader information only and constitutes neither a guarantee nor warranty by the ARS-USDA, nor does it imply approval of the product named to the exclusion of other products. References 1. Lal, R. Soils and world food security. Soil Till. Res. 2009, 102, 1–4. [CrossRef] 2. Hamza, M.A.; Anderson, W.K. Soil compaction in cropping systems. A review of the nature, causes and possible solutions. Soil Till. Res. 2005, 82, 121–145. [CrossRef] 3. Jabro, J.D.; Iversen, W.M.; Evans, R.G.; Allen, B.L.; Stevens, W.B. Repeated freeze-thaw cycles effects on soil compaction in a clay loam in northeastern Montana. Soil Sci. Soc. Am. J. 2014, 78, 737–744. [CrossRef] 4. Jabro, J.D.; Stevens, W.B.; Iversen, W.M.; Sainju, U.M.; Allen, B.L. Soil cone index and bulk density of a sandy loam under no-till and conventional tillage in a corn-soybean rotation. Soil Till. Res. 2020, submitted. 5. Spinelli, R.; Magagnotti, N.; Cavallo, E.; Capello, G.; Biddoccu, M. Reducing soil compaction after thinning work in agroforestry plantations. Agrofor. Syst. 2019, 93, 1765–1779. [CrossRef] 6. Dudáková, Z.; Allman, M.; Merganic, ˇ J.; Merganicov ˇ á, K. Machinery-induced damage to soil and remaining forest stands—Case study from Slovakia. Forests 2020, 11, 1289. [CrossRef] 7. Lal, R. Soil Compaction and Tillage Effects on Soil Physical Properties of a Mollic Ochraqualf in Northwest Ohio. J. Sustain. Agric. 1999, 14, 53–65. [CrossRef] 8. Sidhu, D.; Duiker, S.W. Soil compaction in conservation tillage: Crop impacts. Agron. J. 2006, 98, 1257–1264. [CrossRef] 9. Busscher, W.J.; Sojka, R.E.; Doty, C.W. Residual effects of tillage on Coastal Plain soil strength. Soil Sci. 1986, 141, 144–148. [CrossRef] 10. Raper, R.L.; Schwab, E.B.; Balkcom, K.S.; Burmester, C.H.; Reeves, D.W. Effect annual, biennial, and triennial in-row subsoiling on soil compaction and cotton yield in southeastern U.S. slit loam soils. Appl. Eng. Agric. 2005, 21, 337–343. [CrossRef] Land 2021, 10, 202 10 of 10 11. Rosolem, C.A.; Pivetta, L.A. Mechanical and biological approaches to alleviate soil compaction in tropical soils: Assessed by root growth and activity (Rb uptake) of soybean and maize grown in rotation with cover crops. Soil Use Manag. 2017, 33, 141–152. [CrossRef] 12. Wang, L.; Wang, H.; Tian, Z.; Lu, Y.; Gao, W.; Ren, T. Structural changes of compacted soil layers in northeast china due to freezing-thawing processes. Sustainability 2020, 12, 1587. [CrossRef] 13. Unger, P.W.; Kasper, T.C. Soil compaction and root growth: A review. Agron. J. 1994, 86, 759–766. [CrossRef] 14. Whalley, W.R.; Dumitru, E.; Dexter, A.R. Biological effects of soil compaction. Soil Till. Res. 1995, 35, 53–68. [CrossRef] 15. Williams, S.M.; Weil, R.R. Crop cover root channels may alleviate soil compaction effects on soybean crop. Soil Sci. Soc. Am. J. 2004, 68, 1403–1409. [CrossRef] 16. Chen, G.; Weil, R.R. Penetration of cover crop roots through compacted soils. Plant Soil 2010, 331, 31–43. [CrossRef] 17. Ehlers, W.; Kopke, U.; Hesse, F.; Bohm, W. Penetration resistance and root growth of oats in tilled and untilled loess soil. Soil Till. Res. 1983, 3, 261–275. [CrossRef] 18. Cresswell, H.P.; Kirkegaard, J.A. Subsoil amelioration by plant roots—The process and the evidence. Aust. J. Soil Res. 1995, 33, 221–239. [CrossRef] 19. Jabro, J.D.; Sainju, U.M.; Stevens, W.B.; Lenssen, A.W.; Evans, R.G. Long-term tillage Influences on soil physical properties under dryland conditions in northeastern Montana. Arch. Agron. Soil Sci. 2009, 55, 633–640. [CrossRef] 20. Jacobsen, J.; Jackson, G.; Jones, C. Fertilizer Guidelines for Montana Crops; Publ. EB 161. Mont. State Univ. Ext. Serv.; Montana State University: Bozeman, Montana, 2005. 21. SAS Institute. The SAS System for Windows; Version 9.2; SAS Institute: Cary, NC, USA, 2011. 22. Taylor, H.M.; Gardner, H.R. Penetration of cotton seeding tap root as influenced by bulk density, moisture content and strength of soil. Soil Sci. 1963, 96, 153–156. [CrossRef] 23. Parr, J.F.; Papendick, R.I. Factors affecting the decomposition of crop residues by microorganisms. Crop. residue Manag. Syst. 1978, 31, 101–129. 24. Lal, R.; Wilson, G.F.; Okigbo, B.N. Changes in properties of an Alfisol produced by various crop covers. Soil Sci. 1979, 127, 377–382. [CrossRef] http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Land Multidisciplinary Digital Publishing Institute

Effect of Previous Crop Roots on Soil Compaction in 2 Yr Rotations under a No-Tillage System

Download PDF
10 pages

Loading next page...
 
/lp/multidisciplinary-digital-publishing-institute/effect-of-previous-crop-roots-on-soil-compaction-in-2-yr-rotations-TO8hesjwzB

References (26)

Publisher
Multidisciplinary Digital Publishing Institute
Copyright
© 1996-2021 MDPI (Basel, Switzerland) unless otherwise stated Disclaimer The statements, opinions and data contained in the journals are solely those of the individual authors and contributors and not of the publisher and the editor(s). MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Terms and Conditions Privacy Policy
ISSN
2073-445X
DOI
10.3390/land10020202
Publisher site
See Article on Publisher Site

Abstract

land Article Effect of Previous Crop Roots on Soil Compaction in 2 Yr Rotations under a No-Tillage System Jay D. Jabro *, Brett L. Allen, Tatyana Rand, Sadikshya R. Dangi and Joshua W. Campbell Northern Plains Agricultural Research Laboratory, ARS-USDA, 1500 N Central Avenue, Sidney, MT 59270, USA; brett.allen@usda.gov (B.L.A.); Tatyana.Rand@usda.gov (T.R.); Sadikshya.Dangi@usda.gov (S.R.D.); Joshua.campbell@usda.gov (J.W.C.) * Correspondence: jay.jabro@usda.gov; Tel.: +1-406-433-9442 Abstract: Compacted soils affect global crop productivity and environmental quality. A field study was conducted from 2014 to 2020 in the northern Great Plains, USA, to evaluate the effect of various rooting systems on soil compaction in 2 yr rotations of camelina (Camelina sativa L.), carinata (Brassica carinata A.) and a cover crop mix planted in place of fallow with durum (Triticum durum D.). The study was designed as a randomized complete block with three replications in a no-tillage system. The soil was classified as Dooley sandy loam (fine-loamy, mixed, superactive, frigid Typic Argiustolls) derived from glacial till parent material. Three measurements of soil penetration resistance (PR) were taken with a penetrometer to a depth of 0–30 cm within each plot. Soil moisture contents were determined using a TDR sensor at the time of PR measurements. Both measurements were monitored prior to planting in spring and after harvest. Initial PR results from spring 2014 showed that all plots had an average of 2.244 MPa between the 8–20 cm depth, due to a history of tillage and wheel traffic caused by various field activities. Covariance analysis indicated that soil PR was not significantly affected by crop type and moisture content. After one cycle of the 2 yr rotation, the Citation: Jabro, J.D.; Allen, B.L.; 2016 measurements indicated that the compacted layer existed at the same initial depths. However, Rand, T.; Dangi, S.R.; Campbell, J.W. after two and three cycles, soil PR values were reduced to 1.480, 1.812, 1.775, 1.645 MPa in spring Effect of Previous Crop Roots on Soil 2018 and 1.568, 1.581, 1.476, 1.458 MPa in 2020 under camelina, carinata, cover crop mix, and durum Compaction in 2 Yr Rotations under a treatments, respectively. These findings indicate that previous cover crop roots could effectively No-Tillage System. Land 2021, 10, 202. improve soil compaction by penetrating the compacted layer, decompose over time and form voids https://doi.org/10.3390/ and root channels. Although these results are novel and significant, further research is needed on land10020202 different soils and under cover crops with different root systems to support our findings prior to making any conclusion. Academic Editors: Richard Cruse and Teodor Rusu Keywords: soil compaction; penetration resistance; biological method; root channels; bio-pores Received: 23 December 2020 Accepted: 12 February 2021 Published: 17 February 2021 1. Introduction Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in Soil compaction is a form of degradation affecting future global food security and published maps and institutional affil- continues to be a problem for farmers in many parts of the world [1]. Over the past iations. few decades, management practices and field activities as well as wheel traffic from various heavy farm machinery have led to an increase in soil compaction, prompting global concerns on soil quality, hydrological properties, and crop production [2–6]. It can significantly reduce total soil porosity, change pore size distribution, affect hydrological Copyright: © 2021 by the authors. processes, and impact crop production for food security [1–3,5–8]. Licensee MDPI, Basel, Switzerland. Several approaches have been utilized to alleviate soil compaction in agricultural This article is an open access article lands including mechanical, natural, and biological. Mechanical methods such as deep distributed under the terms and tillage or subsoiling are good practical solutions in alleviating compaction problems in conditions of the Creative Commons subsurface soil layers; however, these processes have detrimental effects on soil quality Attribution (CC BY) license (https:// and organic matter decomposition as well as involving considerable expenditures of time, creativecommons.org/licenses/by/ money and fuel [2,9–11]. 4.0/). Land 2021, 10, 202. https://doi.org/10.3390/land10020202 https://www.mdpi.com/journal/land Land 2021, 10, 202 2 of 10 Natural repeated freezing and thawing cycles and their dynamic forces have been proven effective tools for lessening soil compaction and improving soil physical quality in the top layers over winter periods in cold regions [3,12]. Biological methods such as deep-rooted cover crops can be another potential solution to ameliorate the negative effects of soil compaction, particularly in no-tillage farming production [11,13,14]. Cover crops (e.g., radish, safflower, turnip, etc.) with vigorous taproots can reduce soil compaction by penetrating and loosening the compacted layer. Eventually, these roots decompose over time and form root channels and large voids that enable air, water, nutrient and roots of subsequent crops to move more deeply through the soil profile, thus enhancing soil macropores and physical quality [15,16]. Some researches refer to this biological process as a “bio-drilling” or “biological drilling” or “bio-tillage” which is the root-induced formation of voids “bio-pores” that present deep paths for air, water, nutrient movement, and root growth, and penetration of subsequent crops [15–18]. Ehlers et al. [17] evaluated soil penetration resistance and root growth of oats in tilled and untilled soils. They concluded that root channels or “bio-pores” created by roots of preceding crops acted as passages for subsequent crops in the soil profile in no-tillage systems. Williams and Weil [15] observed that soybean roots grew through the compacted plow pan soil using channels and “bio-pores” created by decomposition of cover crop roots. Similarly, Chen and Weil [16] evaluated the effect of three cover crop roots in compacted soils. They concluded that forage radish and rapeseed had at least twice as many roots as rye in a highly compacted soil and determined that tap-rooted crops may penetrate the compacted soil layer far better than fibrous-rooted crops. Recently, Rosolem and Pivetta [11] investigated both mechanical and biological meth- ods to alleviate soil compaction in tropical clay soils. In their study, they evaluated root growth and activity of soybean and maize grown in rotation with cover crops. They found that including ruzi grass and castor cover crops in the rotation increased root growth, activity and “bio-pores” in the soil profile as well as increased soybean yield. We hypothesized that cover crops and cool-season oilseed crops with different root systems (i.e., vigorous taproots, fibrous roots) would have a potential to alleviate soil compaction in agricultural lands. Globally, soil compaction can affect crop productivity and millions of hectares are affected by soil compaction that cost farmers millions of dollars every year. Crop roots can improve compacted soils and eliminate the need for expensive tillage operations, which tend to provide only a short-term benefit while reversing benefits of no-till production on soil quality. Further, information about using crop roots as an approach to biologically managing and loosening compacted soils in the MonDak region (eastern Montana and western North Dakota, USA) of the northern Great Plains is lacking. Therefore, the objective of this study was to evaluate the effect of previous crop roots on soil compaction in 2 yr durum wheat rotations with camelina, carinata and a cover crop mix planted in place of fallow in a no-tillage farming system. 2. Materials and Methods 2.1. Field Experiment A long-term field study was carried out from 2014 to 2020 at the USDA-ARS dryland 0  0 site located approximately 11 km north of Culbertson (48 33 N, 104 50 W, altitude 589 m) in the northern Great Plains, USA. The soil at the research site was classified as Dooley sandy loam (fine-loamy, mixed, superactive, frigid Typic Argiustolls) (https://soilseries.sc. egov.usda.gov (accessed on 16 February 2021)), derived from glacial till parent material, with a slope of 0 to 2%. The amounts of sand, silt, and clay in Ap horizon (0–15 cm) were approximately 62%, 22%, and 16%, respectively, and in Bt (15–30 cm) horizon were approximately 60%, 21%, and 19%, respectively. The presence of argillic horizon in this layer can greatly restrict water flow, root development and has higher density values and less macropores. The soil sampled prior to initiation of this experiment contained Land 2021, 10, 202 3 of 10 approximately 1.7% organic matter and has 7.2 pH at the 0–20 cm depth [19]. Monthly precipitation amounts during 2014–2020 growing seasons at the study site are given in Table 1. The previous cropping system was continuous spring or spring wheat–summer fallow at this site for over 30 years. Annual tillage to a depth of 15 to 20 cm was typical prior to 2005 to control weeds and prepare the seedbed for planting. Thereafter, no-tillage was practiced and weeds were controlled with herbicides. The moldboard plow has not been used at this field for over 25 years. Table 1. Monthly precipitation from April to September during 2014–2020 growing seasons at the research site near Culbertson, MT, USA. Precipitation, mm Average Month 2014 2015 2016 2017 2018 2019 2020 April 30.5 5.1 47.8 4.6 35.3 34.5 6.1 23.4 May 39.9 32.3 51.8 7.9 62.0 31.0 45.5 38.6 June 62.5 82.3 101.1 12.2 55.9 75.9 46.7 62.4 July 25.1 42.9 63.2 34.3 76.2 46.5 73.7 51.7 August 70.6 44.7 4.1 45.7 14.7 124.5 1.2 43.6 September 18.3 33.0 78.5 47.5 51.1 169.7 0 56.9 Total 246.9 240.3 346.5 152.2 294.2 482.1 173.2 276.5 Crops in a 2 yr rotation with durum wheat (Triticum durum D.) were camelina (Camelina sativa L.), carinata (Brassica carinata A.), both belonging to the Brassicace family, and a cover crop mix (10 species). The cover crop mix was composed of 12% lentil (Lens culinaris), 19% forage pea (Pisum sativum), 6% radish (Raphanus sativus), 3% turnip (Brassica rapa subsp), 3% winter canola (Brassica napus), 6% flax (Linum usitatissimum), 13% forage sorghum (Sorghum vulgare Pers), 6% German millet (Setaria italic), 19% cowpea (Vigna unguiculata), and 13% buckwheat (Fagopyrum esculentum). We planted a diversified cover crop mix to maximize ecosystem services with inclusion of functional groups including pollinator species, warm and cool season plants, broadleafs and grasses, legumes, and crucifer species. A highly variable climate in the region typically favors different species productivity among years, hence the desire to plant a highly diversified cover crop mix. Planting for all crops in the study took place in late April to early May using a custom built no-till research drill with double-shoot Barton single-disk openers on 20.3 cm row spacing. Durum “Grenora” was planted at 67 kg ha . Camelina “Suneson”, carinata “A110”, and the cover crop mix were planted at 9.0, 7.3, and 26.9 kg ha . Crop seeds were harvested with a Kincaid 8XP research combine (manufactured in Haven, KS, USA). Camelina seed was typically harvested late July to early August; durum harvest was early to mid-August. Carinata seed was harvested late August to mid-September. The cover crop mix was swathed for forage at pea bloom, typically occurring in mid-July. Following forage harvest, the cover crop was allowed to regrow unharvested and was terminated each year with a killing frost that typically occurred late September to mid-October. Fertilizer was banded at planting 5 cm below and 5 cm to the side of seed. Urea (45-0-0) was applied to durum, camelina, and carinata based on yield goals of 2350, 1800, 1 1 and 1800 kg ha , resulting in N application rates of 129, 90, and 117 kg ha , respectively, according to fertilizer guidelines for Montana crops [20]. Urea rates were adjusted by subtracting N from monoammonium phosphate and ammonium sulfate fertilizer and from residual soil nitrate that was determined from soil samples (0–60 cm depth) taken the previous fall. All plots received 56 and 45 kg ha monoammonium phosphate (11-52-0) and potassium chloride (0-0-60) and camelina and carinata plots received 112 kg ha ammonium sulfate (20-0-0-24) banded at planting. Weed control consisted of preplant and post-harvest applications of glyphosate her- –1 –1 bicide at 3.36 kg a.i. ha . Durum also received an in-crop application of 0.68 kg a.i. ha –1 bromoxynil and 0.09 kg a.i ha fenoxaprop herbicides. Camelina and carinata received –1 9.0 kg a.i. ha ethylfluralin in late fall preceding spring planting. Land 2021, 10, 202 4 of 10 Research plots in the rotation were arranged in randomized complete block design with three replications. Each crop phase of the rotation was present in every year for a total of 18 plots from three different rotations. Each plot measured 6 m wide  15 m long. 2.2. Field Measurements Soil penetration resistance (PR) was measured using a hand-held digital stainless steel cone-tipped penetrometer (12.8 mm diameter, 30 cone) (Field Scout, SC 900 Soil Compaction Meter; Spectrum Technologies, Inc., Plainfield, IL, USA). Measurements were made at three locations on a diagonal transect across each plot, one at the middle of the plot and the other two at each end of the plot. Penetration resistance readings (MPa) were recorded to the 30 cm depth at intervals of 2.5 cm [3,19]. At the time of PR measurements, soil moisture contents were determined for each plot using a digital TDR at three measurements per plot adjacent to PR positions (Field Scout, TDR 300 Soil Moisture Meter; Spectrum Technologies, Inc., Plainfield, IL, USA. Soil PR and volumetric moisture content were monitored shortly after planting and after harvest in each plot every year throughout the course of the study. Measurements were taken on 13 May, 11 September in 2014; 30 April, 11 September in 2015; 2 May, 26 September in 2016; 5 May, 4 October in 2017; 3 May, 2 October in 2018; 8 May, 8 October in 2019; and 21 April in 2020. 2.3. Statistical Analysis The mixed model of SAS was used for data analysis [21] using repeated measures over time as randomized block model with previous crop as a fixed effect, and year and replication as random effects. The variables PR and volumetric moisture content measured by the TDR were tested for linearity and a significant linear correlation was found between these two soil parame- ters (r = 0.254, p = 0.009). Therefore, analysis of covariance was used to analyze soil PR for the compacted layer of 8–20 cm depth using moisture content as a covariable parameter. Mean separation utilized least significant differences at p  0.05. 3. Results and Discussion Statistical results from analysis of covariance indicated that soil PR varied significantly by year (p < 0.0001) and not significantly by previous crop (p = 0.0554), with a significant interaction for previous crop  year (p = 0.0014). Results indicated that the effect of previous crop on soil moisture content was not significant in all six years (Table 2). Table 2. Mean values of volumetric moisture content (%) across 0–20 cm depth as affected by previous crop (spring measurements) in the compacted layer (8–20 cm) for 2015–2020 growing seasons. Volumetric Moisture Content, % Previous Crop 2015 2016 2017 2018 2019 2020 Camelina 21.18 20.61 19.52 20.78 20.71 19.47 Carinata 22.57 19.67 19.87 21.28 20.99 20.06 Cover crop mix 20.36 20.26 19.51 21.06 20.29 20.05 Durum 20.67 21.19 19.51 20.82 20.20 20.10 The effects of previous crop on soil PR and volumetric moisture content in the com- pacted layer of 8–20 cm for the 2015, 2016, 2017, 2018, 2019, and 2020 growing seasons are presented in Table 3. The effect of previous crop on soil PR was not significant in all years except in 2015 and 2017. Variations in the PR among crops in 2015 and 2017 may be related to the soil variability within the field (Table 3). Land 2021, 10, 202 5 of 10 Table 3. Analysis of covariance results showing the effect of previous crop on mean soil penetration resistance (spring measurements) of the compacted layer (8–20 cm) for the 2015–2020 growing seasons. Penetration Resistance, MPa Previous Crop 2015 2016 2017 2018 2019 2020 Camelina 2.503a 2.112a 2.930ab 1.480b 1.863a 1.568a Carinata 2.600a 2.475a 2.707a 1.812a 2.115a 1.581a Cover crop mix 2.252ab 2.563a 3.134b 1.775a 1.949a 1.476a Durum 2.027b 2.328a 2.698a 1.645a 2.175a 1.458a Analysis of covariance Effect p > F Previous crop 0.0211 0.0986 0.0303 0.1245 0.1731 0.2293 Moisture 0.0882 0.8208 0.5205 0.6274 0.0963 0.8019 content In 2014, average soil penetration resistance for the compacted layer (8–20 cm) was 2.244 MPa where durum was a previous crop in all plots. Numbers followed by different lowercase letters within a column in a set are significantly different at p = 0.05. In 2014, soil PR averaged across all 18 plots was 2.244 MPa where durum or spring wheat was a previous crop for over 30 years. Results from 2014 showed all plots had a compacted layer that exceeded the critical compaction level of 2 MPa between the 8–20 cm depth [22], presumably due to a history of tillage that likely caused a plow pan layer, Land 2021, 10, x FOR PEER REVIEW 6 of 10 presence of argillic horizon, continuous monocropping of spring wheat, and wheel traffic caused by other farming activities and management practices (Figure 1). Penetration resistance, MPa 0.00.5 1.01.5 2.02.5 3.0 All plots 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Figure 1. Initial mean soil penetration resistance across all plots in 2014, and across camelina, carinata, Figure 1. Initial mean soil penetration resistance across all plots in 2014, and across camelina, cari- cover crop mix, and durum after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in 2020. nata, cover crop mix, and durum after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in Average soil penetration resistance across camelina, carinata, cover crop mix, and du- rum plots for the 8–20 cm layer after one, two, and three cycles of the 2 yr rotation were Similarly, soil PR from 0 to 30 cm depth under camelina, carinata, cover crop mix, 2.370, 1.678, and 1.521 MPa in 2016, 2018, and 2020, respectively. and durum are presented in Figures 2–5, respectively. Soil penetration resistance for the After one cycle of the 2 yr rotation (2014–2016), soil PR measured in spring 2016 indicated compacted layer under these crops exhibited similar patterns as described in Figure 1. that the compacted layer continued to exist at the same depth of 8–20 cm. After two cycles (2014–2018), soil PR measurements in spring 2018 indicated that the compacted layer was Penetration resistance, MPa 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Camelina 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Figure 2. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in 2020 for camelina as a previous crop. Depth, cm Depth, cm Land 2021, 10, x FOR PEER REVIEW 6 of 10 Penetration resistance, MPa 0.00.5 1.01.5 2.02.5 3.0 All plots 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Land 2021, 10, 202 6 of 10 Figure 1. Initial mean soil penetration resistance across all plots in 2014, and across camelina, cari- decreased below the critical level of 2 MPa by 25.2% regardless of the rooting characteristics nata, cover crop mix, and durum after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in of the rotation crops. After three cycles (2014–2020), soil PR measurements in spring 2020 indicated that the compacted layer was reduced once again by 32.2% (Figure 1). Similarly, soil PR from 0 to 30 cm depth under camelina, carinata, cover crop mix, Similarly, soil PR from 0 to 30 cm depth under camelina, carinata, cover crop mix, and and durum durum ar are presented e presented in in Figu Figures res 2–5, respecti 2–5, respectively vely. Soi . Soil l penetration penetration resista resistance nce f for or the the compacted layer under these crops exhibited similar patterns as described in Figure 1. compacted layer under these crops exhibited similar patterns as described in Figure 1. Penetration resistance, MPa 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Camelina 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Land 2021, 10, x FOR PEER REVIEW 7 of 10 Figure 2. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, Figure 2. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in 2020 for camelina as a previous crop. after 2 cycles in 2018, and after 3 cycles in 2020 for camelina as a previous crop. Penetration resistance, MPa 0.00.5 1.01.5 2.02.5 3.0 Carinata 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Figure 3. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, Figure 3. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in 2020 for carinata as a previous crop. after 2 cycles in 2018, and after 3 cycles in 2020 for carinata as a previous crop. Penetration resistance, MPa 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Cover crop mix 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Figure 4. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in 2020 for cover crop mix as a previous crop. Depth, cm Depth, cm Depth, cm Depth, cm Land 2021, 10, x FOR PEER REVIEW 7 of 10 Penetration resistance, MPa 0.00.5 1.01.5 2.02.5 3.0 Carinata 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Land 2021, 10, 202 7 of 10 Figure 3. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in 2020 for carinata as a previous crop. Penetration resistance, MPa 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Cover crop mix 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Land 2021, 10, x FOR PEER REVIEW 8 of 10 Figure 4. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, Figure 4. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in 2020 for cover crop mix as a previous crop. after 2 cycles in 2018, and after 3 cycles in 2020 for cover crop mix as a previous crop. Penetration resistance, MPa 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Durum 2014, initial 2016, after 1 cycle 2018, after 2 cycles 2020, after 3 cycles Figure 5. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, Figure 5. Initial mean soil penetration resistance across all plots in 2014 and after 1 cycle in 2016, after 2 cycles in 2018, and after 3 cycles in 2020 for durum as a previous crop. after 2 cycles in 2018, and after 3 cycles in 2020 for durum as a previous crop. After one cycle of the 2 yr rotation (2014–2016), soil PR measured in spring 2016 under After one cycle of the 2 yr rotation (2014–2016), soil PR measured in spring 2016 un- camelina, carinata, cover crop mix, and durum indicated that the compacted layer was der camelina, carinata, cover crop mix, and durum indicated that the compacted layer was present at the 8–20 cm depth. After two and three cycles, soil PR in the compacted layer present at the 8–20 cm depth. After two and three cycles, soil PR in the compacted layer was decreased below the threshold of 2 MPa under each crop. Reductions in soil PR in was decreased below the threshold of 2 MPa under each crop. Reductions in soil PR in the the compacted layer after two and three cycles under camelina, carinata, cover crop mix, compacted layer after two and three cycles under camelina, carinata, cover crop mix, and and durum are given in Table 4. These reductions ranged between 19.3–34% and 29.5–35% durum are given in Table 4. These reductions ranged between 19.3–34% and 29.5–35% after two and three cycles, respectively. after two and three cycles, respectively. Table 4. Reduction in soil penetration resistance in the compacted layer (8–20 cm) for durations 2014–2018 and 2014–2020 under camelina, carinata, cover crop mix, and durum. Reduction in Soil Penetration Resistance, % Previous Crop 2014–2018 2014–2020 Camelina 34.0 30.1 Carinata 19.3 29.5 Cover crop mix 20.9 34.2 Durum 26.7 35.0 All plots (average) 25.2 32.2 The root systems of cover crop mix and durum tended to have greater effects in loos- ening the compacted soil by creating more root channels and voids than both camelina and carinata after three cycles of the rotation (Table 4). The cover crop mix treatment had various crops with a vigorous taproot system such as radish, forage sorghum, and turnip that penetrated through the compacted soil layer, decomposed over time, and created voids and passages through the dense layer. Concluding results indicated that root systems of cover crops used in this study re- quired approximately four years to be decomposed and produced root channels and pore spaces in the compacted soil profile. These findings showed that roots of camelina, cari- nata, cover crop mix, and durum could have a potential to decrease soil penetration re- Depth, cm Depth, cm Depth, cm Land 2021, 10, 202 8 of 10 Table 4. Reduction in soil penetration resistance in the compacted layer (8–20 cm) for durations 2014–2018 and 2014–2020 under camelina, carinata, cover crop mix, and durum. Reduction in Soil Penetration Resistance, % Previous Crop 2014–2018 2014–2020 Camelina 34.0 30.1 Carinata 19.3 29.5 Cover crop mix 20.9 34.2 Durum 26.7 35.0 All plots (average) 25.2 32.2 The root systems of cover crop mix and durum tended to have greater effects in loosening the compacted soil by creating more root channels and voids than both camelina and carinata after three cycles of the rotation (Table 4). The cover crop mix treatment had various crops with a vigorous taproot system such as radish, forage sorghum, and turnip that penetrated through the compacted soil layer, decomposed over time, and created voids and passages through the dense layer. Concluding results indicated that root systems of cover crops used in this study Land 2021, 10, x FOR PEER REVIEW 9 of 10 required approximately four years to be decomposed and produced root channels and pore spaces in the compacted soil profile. These findings showed that roots of camelina, carinata, cover crop mix, and durum could have a potential to decrease soil penetration resistance in sistance in the compacted layer by penetrating the compacted layer, eventually decom- the compacted layer by penetrating the compacted layer, eventually decompose, and form pose, and form biological voids and channels, which enable air, water, nutrient and root biological voids and channels, which enable air, water, nutrient and root growth for following crops growt to move h for easily follow thr ing crop ough the s to compacted move easily through the compa layer. cted layer. Figure 6 shows roots for various crops (sorghum, radish, turnip, etc.) in the cover Figure 6 shows roots for various crops (sorghum, radish, turnip, etc.) in the cover crop mix treatment crop mi growing x trea andtpenetrating ment growin thr g a ough nd penetrati the compacted ng through t soil h layer e compa in summer cted soil la of yer in summer 2017. These roots of 2017. These roots will d will decompose over time eco and mpose ov form lar er time ge voids and and form large vo root channels ids in and the root channels in compacted layer. the compacted layer. Figure 6. An image showing roots for (A) sorghum and (B) turnip through dense soil layers in the Figure 6. An image showing roots for (A) sorghum and (B) turnip through dense soil layers in the cover crop mix treat- ment. cover crop mix treatment. The decomposition rate of cover crop roots and plant residues primarily depends on The decomposition rate of cover crop roots and plant residues primarily depends on many factors including soil aeration, moisture content, temperature, texture, acidity, tillage, many factors including soil aeration, moisture content, temperature, texture, acidity, till- crop species, nitrogen availability, plant characteristics as well as microbial diversity and age, crop species, nitrogen availability, plant characteristics as well as microbial diversity activities in the soil [23]. and activities in the soil [23]. The results of the study confirm previous research that showed that tap-rooted crops The results of the study confirm previous research that showed that tap-rooted crops are more effective than fibrous-rooted crops in ameliorating compacted soils [16,18,24]. are more effective than fibrous-rooted crops in ameliorating compacted soils [16,18,24]. Nevertheless, further investigations on different textured soils with various tap-rooted Nevertheless, further investigations on different textured soils with various tap-rooted crops (i.e., rye grass, radish, safflower, turnip, Lucerne or alfalfa, rape, sugarbeet, chicory, crops (i.e., rye grass, radish, safflower, turnip, Lucerne or alfalfa, rape, sugarbeet, chicory, etc.) as well as cover crops with fibrous-rooted crops are required for conclusive recom- mendations on crop rotations to avoid/recover from soil compaction in a no-tillage sys- tem. 4. Conclusions Overall, after two cycles of the 2 yr rotation, soil PR measurements in 2018 indicated that the compacted layer was decreased below the threshold of 2 MPa, by 25.2% (1.706 MPa) in sandy loam soil. After three cycles, PR measurements in 2020 indicated that the compacted layer was reduced once again by 32.2% (1.480 MPa). These findings indicate that previous crop roots could effectively decrease soil compaction. Results indicated that crop roots required approximately 4–6 years to decompose and produce root channels and bio-voids through the soil compacted layer. Our results showed that decayed cover crop roots over time could combat soil compaction. More re- search is needed to confirm these results on different soils and using various deep-rooted crops with vigorous taproots as well as cover crops with fibrous roots prior to making any explicit conclusion. Roots of cover crop species may differ in their ability to grow and penetrate the compacted soil layers as well as in their decomposition rates in different soils and under various environments. Author Contributions: Conceptualization, J.D.J., and B.L.A.; methodology, J.D.J. and B.L.A.; writ- ing—original draft preparation, J.D.J.; statistics, J.D.J.; writing—review and editing, J.D.J., and Land 2021, 10, 202 9 of 10 etc.) as well as cover crops with fibrous-rooted crops are required for conclusive recom- mendations on crop rotations to avoid/recover from soil compaction in a no-tillage system. 4. Conclusions Overall, after two cycles of the 2 yr rotation, soil PR measurements in 2018 indicated that the compacted layer was decreased below the threshold of 2 MPa, by 25.2% (1.706 MPa) in sandy loam soil. After three cycles, PR measurements in 2020 indicated that the com- pacted layer was reduced once again by 32.2% (1.480 MPa). These findings indicate that previous crop roots could effectively decrease soil compaction. Results indicated that crop roots required approximately 4–6 years to decompose and produce root channels and bio-voids through the soil compacted layer. Our results showed that decayed cover crop roots over time could combat soil compaction. More research is needed to confirm these results on different soils and using various deep-rooted crops with vigorous taproots as well as cover crops with fibrous roots prior to making any explicit conclusion. Roots of cover crop species may differ in their ability to grow and penetrate the compacted soil layers as well as in their decomposition rates in different soils and under various environments. Author Contributions: Conceptualization, J.D.J., and B.L.A.; methodology, J.D.J. and B.L.A.; writing— original draft preparation, J.D.J.; statistics, J.D.J.; writing—review and editing, J.D.J., and B.L.A.; visualization, J.D.J.; funding acquisition, B.L.A.;investigation, J.D.J., B.L.A., T.R., S.R.D., and J.W.C.; project administration, J.D.J., B.L.A., T.R., S.R.D., and J.W.C; review and editing, T.R., S.R.D., and J.W.C. All authors have read and agreed to the published version of the manuscript. Funding: This research was supported by Agrisoma Biosciences Inc., 200, Rue Montcalm, Suite 300 Gatineau, Quebec J8Y 3B5. Data Availability Statement: Data have already been provided within the manuscript. However, other relevant data or information can be requested from the authors. Acknowledgments: We acknowledge the help of Dale Spracklin with soil measurements during the course of this study. Conflicts of Interest: The authors declare no conflict of interest. Disclaimer: Mention of trade names, proprietary products, or specific equipment is intended for reader information only and constitutes neither a guarantee nor warranty by the ARS-USDA, nor does it imply approval of the product named to the exclusion of other products. References 1. Lal, R. Soils and world food security. Soil Till. Res. 2009, 102, 1–4. [CrossRef] 2. Hamza, M.A.; Anderson, W.K. Soil compaction in cropping systems. A review of the nature, causes and possible solutions. Soil Till. Res. 2005, 82, 121–145. [CrossRef] 3. Jabro, J.D.; Iversen, W.M.; Evans, R.G.; Allen, B.L.; Stevens, W.B. Repeated freeze-thaw cycles effects on soil compaction in a clay loam in northeastern Montana. Soil Sci. Soc. Am. J. 2014, 78, 737–744. [CrossRef] 4. Jabro, J.D.; Stevens, W.B.; Iversen, W.M.; Sainju, U.M.; Allen, B.L. Soil cone index and bulk density of a sandy loam under no-till and conventional tillage in a corn-soybean rotation. Soil Till. Res. 2020, submitted. 5. Spinelli, R.; Magagnotti, N.; Cavallo, E.; Capello, G.; Biddoccu, M. Reducing soil compaction after thinning work in agroforestry plantations. Agrofor. Syst. 2019, 93, 1765–1779. [CrossRef] 6. Dudáková, Z.; Allman, M.; Merganic, ˇ J.; Merganicov ˇ á, K. Machinery-induced damage to soil and remaining forest stands—Case study from Slovakia. Forests 2020, 11, 1289. [CrossRef] 7. Lal, R. Soil Compaction and Tillage Effects on Soil Physical Properties of a Mollic Ochraqualf in Northwest Ohio. J. Sustain. Agric. 1999, 14, 53–65. [CrossRef] 8. Sidhu, D.; Duiker, S.W. Soil compaction in conservation tillage: Crop impacts. Agron. J. 2006, 98, 1257–1264. [CrossRef] 9. Busscher, W.J.; Sojka, R.E.; Doty, C.W. Residual effects of tillage on Coastal Plain soil strength. Soil Sci. 1986, 141, 144–148. [CrossRef] 10. Raper, R.L.; Schwab, E.B.; Balkcom, K.S.; Burmester, C.H.; Reeves, D.W. Effect annual, biennial, and triennial in-row subsoiling on soil compaction and cotton yield in southeastern U.S. slit loam soils. Appl. Eng. Agric. 2005, 21, 337–343. [CrossRef] Land 2021, 10, 202 10 of 10 11. Rosolem, C.A.; Pivetta, L.A. Mechanical and biological approaches to alleviate soil compaction in tropical soils: Assessed by root growth and activity (Rb uptake) of soybean and maize grown in rotation with cover crops. Soil Use Manag. 2017, 33, 141–152. [CrossRef] 12. Wang, L.; Wang, H.; Tian, Z.; Lu, Y.; Gao, W.; Ren, T. Structural changes of compacted soil layers in northeast china due to freezing-thawing processes. Sustainability 2020, 12, 1587. [CrossRef] 13. Unger, P.W.; Kasper, T.C. Soil compaction and root growth: A review. Agron. J. 1994, 86, 759–766. [CrossRef] 14. Whalley, W.R.; Dumitru, E.; Dexter, A.R. Biological effects of soil compaction. Soil Till. Res. 1995, 35, 53–68. [CrossRef] 15. Williams, S.M.; Weil, R.R. Crop cover root channels may alleviate soil compaction effects on soybean crop. Soil Sci. Soc. Am. J. 2004, 68, 1403–1409. [CrossRef] 16. Chen, G.; Weil, R.R. Penetration of cover crop roots through compacted soils. Plant Soil 2010, 331, 31–43. [CrossRef] 17. Ehlers, W.; Kopke, U.; Hesse, F.; Bohm, W. Penetration resistance and root growth of oats in tilled and untilled loess soil. Soil Till. Res. 1983, 3, 261–275. [CrossRef] 18. Cresswell, H.P.; Kirkegaard, J.A. Subsoil amelioration by plant roots—The process and the evidence. Aust. J. Soil Res. 1995, 33, 221–239. [CrossRef] 19. Jabro, J.D.; Sainju, U.M.; Stevens, W.B.; Lenssen, A.W.; Evans, R.G. Long-term tillage Influences on soil physical properties under dryland conditions in northeastern Montana. Arch. Agron. Soil Sci. 2009, 55, 633–640. [CrossRef] 20. Jacobsen, J.; Jackson, G.; Jones, C. Fertilizer Guidelines for Montana Crops; Publ. EB 161. Mont. State Univ. Ext. Serv.; Montana State University: Bozeman, Montana, 2005. 21. SAS Institute. The SAS System for Windows; Version 9.2; SAS Institute: Cary, NC, USA, 2011. 22. Taylor, H.M.; Gardner, H.R. Penetration of cotton seeding tap root as influenced by bulk density, moisture content and strength of soil. Soil Sci. 1963, 96, 153–156. [CrossRef] 23. Parr, J.F.; Papendick, R.I. Factors affecting the decomposition of crop residues by microorganisms. Crop. residue Manag. Syst. 1978, 31, 101–129. 24. Lal, R.; Wilson, G.F.; Okigbo, B.N. Changes in properties of an Alfisol produced by various crop covers. Soil Sci. 1979, 127, 377–382. [CrossRef]

Journal

Land – Multidisciplinary Digital Publishing Institute

Published: Feb 17, 2021

There are no references for this article.