No-till Corn-soybean Rotation Research Articles

Agronomic and economic implications of cover crop and phosphorus fertilizer management practices for water quality improvement.

Phosphorus (P) fertilization practices and winter cover crops are promoted to protect water quality yet can potentially influence crop yield and profitability. This study examined the impacts of three P fertilizer management practices (no P, fall broadcast P, and spring injected P) and winter annual cover crop use on yields, net returns, and water quality in a no-till corn-soybean rotation. Treatments were replicated in a 4-yr field study where sediment, total P, and dissolved reactive P (DRP) losses in edge-of-field surface runoff were continuously monitored. Production budgets were developed for each treatment and coupled with water quality data to identify optimal practices and opportunity costs for improving water quality. Applying P fertilizers increased crop yield regardless of application method or cover crop, but the response was more pronounced in corn than soybean. The cover crop reduced corn grain yield in 1 yr with high temperature and low precipitation but did not impact grain yield in the other corn year or either year of soybean. The most profitable treatment was fall broadcast P fertilizer with no cover crop, which also had the greatest total P and DRP losses and near greatest sediment loss. The lowest-cost methods of reducing total P, DRP, and sediment losses were, respectively, no P fertilizer without a cover crop ($47.56kg-1 total P), spring injected P fertilizer without a cover crop ($56.47kg-1 DRP), and spring injected P fertilizer with a cover crop ($0.16kg-1 sediment). Widespread adoption of these practices will likely require monetary incentives.

Influence of Spatial Planting Arrangement of Winter Rye Cover Crop on Corn Seedling Disease and Corn Productivity.

Despite numerous environmental benefits associated with cover crop (CC) use, some farmers are reluctant to include CCs in their production systems because of reported yield declines in corn. There are numerous potential reasons for this yield decline, including seedling disease. A winter rye CC can serve as a "green bridge" for corn seedling pathogens. We hypothesized that proximity of corn seedling roots to decaying rye CC roots contributes to corn seeding disease. An experimental field plot and an on-farm study were conducted over 2 years to evaluate growth, development, and disease severity of corn seedlings planted at various distances from decaying winter rye CC plants. The experimental field plot study was conducted in a no-till corn-soybean rotation with five replications of a winter rye CC treatment seeded as (i) no-CC control, (ii) broadcast, (iii) 19-cm drilled rows, and (iv) 76-cm drilled rows. The on-farm study was no-till corn-soybean rotation with four replications of a winter rye CC seeded as 38-cm drilled rows, 76-cm drilled rows, and no-CC control. The corn was planted on 76-cm rows shortly after rye was terminated. With multiple seeding arrangements of winter rye, corn was planted at different distances from winter rye. Corn radicle root rot severity and incidence, shoot height, shoot dry weight, corn height and chlorophyll at VT (tasseling), ear parameters, and yield were collected. Soil samples were taken in the corn row and the interrow at winter rye termination, corn planting, and corn growth stage V3 (three leaves with fully developed collars) to estimate the abundance of Pythium clade B members present in soil samples. Our results showed that increased distance between winter rye residue and corn reduced seedling disease and Pythium clade B populations in the radicles and soil and increased shoot dry weight, leaf chlorophyll, plant height, and yield. This suggests that physically distancing the corn crop from the winter rye CC is one way to reduce the negative effects of a winter rye CC on corn.

Responses of leached nitrogen concentrations and soil health to winter rye cover crop under no-till corn-soybean rotation in the northern Great Plains.

Winter rye (Secale cereale L.) is an important cover crop (CC) in the northern Great Plains (NGP), yet concerns over its establishment under the variable weather conditions of this region are an important limitation for its widespread adoption. This study evaluated the impacts of no-till corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation with winter rye CC established in 2017 on (a) water quality (nitrate-N [NO3 - -N], ammonia-N [NH4 + -N], and total nitrogen [TN]) and (b) soil health parameters at the 0-to-15-cm depth. Data showed that rye CC biomass was 251kg ha-1 in 2018, 1,213kg ha-1 in 2019, and 147kg ha-1 in 2020, coinciding with contrasting growing degree days for rye CC (i.e., 1,458, 2,042, and 794, respectively), as a consequence of variable weather conditions. Water quality was not affected for the periods when rye growth was<300kg ha-1 . In the season when rye CC had greater biomass (1,213kg ha-1 ), significant reductions in leached NO3 - -N (19-20%) and TN (8.5-16%) concentrations were observed due to greater N uptake by rye CC (18.8kg N ha-1 ). Rye CC showed significantly (p ≤ .05) higher microbially active carbon ( ∼13%) and water-extractable organic N(∼11%) than the control treatment. Nonsignificant impacts on soil health indicators due to rye CC showed that the study duration (3 yr) may not be sufficient to see the beneficial impacts of CCs on soils. However, significant reductions in leached NO3 - -N and TN concentrations for one (2019) out of three study years suggest that rye with optimal growth has the potential of reducing N leaching and enhancing soil health for the NGP region.

Cover crop and phosphorus fertilizer management impacts on surface water quality from a no-till corn-soybean rotation

Best management practices that reduce potential phosphorus (P) loss and provide flexibility in P fertilizer management are needed to help producers protect water quality while maintaining crop yield. This study examined the impacts of P fertilizer management (no P, fall broadcast P, and spring injected P) and cover crop use on annual concentrations and loads of sediment, total P, and dissolved reactive P (DRP) in edge-of-field runoff from a no-till corn (Zea mays)-soybean (Glycine max) rotation in the Central Great Plains, USA, from September 2015 through September 2019. The spring injected P fertilizer treatment generally had 19% less total P and 33% less DRP loss compared to the fall broadcast treatment, confirming the importance of P fertilizer management as a practice for reducing P loss. The addition of a cover crop had an inconsistent effect on total P loss, with no effect in 2016 and 2017, increasing loss in 2018 by 56%, and decreasing it in 2019 by 40%. The inconsistent impact of cover crops on total P loss was related to cover crop effects on sediment loss. Although cover crop impacts on total P losses were inconsistent, the addition of a cover crop increased DRP loss in three of four years. Cover crop use consistently reduced sediment loss, with greater sediment reduction when P fertilizer was applied. Results from this study highlight the benefit of cover crops for reducing sediment loss and the continued need for proper fertilizer management to reduce P loss from agricultural fields.

Early corn stand count of different cropping systems using UAV-imagery and deep learning

Optimum plant stand density and uniformity is vital in order to maximize corn (Zea mays L.) yield potential. Assessment of stand density can occur shortly after seedlings begin to emerge, allowing for timely replant decisions. The conventional methods for evaluating an early plant stand rely on manual measurement and visual observation, which are time consuming, subjective because of the small sampling areas used, and unable to capture field-scale spatial variability. This study aimed to evaluate the feasibility of an unmanned aerial vehicle (UAV)-based imaging system for estimating early corn stand count in three cropping systems (CS) with different tillage and crop rotation practices. A UAV equipped with an on-board RGB camera was used to collect imagery of corn seedlings (~14 days after planting) of CS, i.e., minimum-till corn-soybean rotation (MTCS), no-till corn-soybean rotation (NTCS), and no-till corn-corn rotation with cover crop implementation (NTCC). An image processing workflow based on a deep learning (DL) model, U-Net, was developed for plant segmentation and stand count estimation. Results showed that the DL model performed best in segmenting seedlings in MTCS, followed by NTCS and NTCC. Similarly, accuracy for stand count estimation was highest in MTCS (R2 = 0.95), followed by NTCS (0.94) and NTCC (0.92). Differences by CS were related to amount and distribution of soil surface residue cover, with increasing residue generally reducing the performance of the proposed method in stand count estimation. Thus, the feasibility of using UAV imagery and DL modeling for estimating early corn stand count is qualified influenced by soil and crop management practices.

Simulated long-term effect of wheat cover crop on soil nitrogen losses from no-till corn-soybean rotation under different rainfall patterns

Soil nitrogen dynamics is affected by the interaction of cover crops and rainfall amount and distribution in rainfed agricultural production systems. There is a lack of understanding on soil nitrogen losses from cover crop-based based cropping systems receiving different rainfall amounts. A simulation model, RZWQM2 (Root Zone Water Quality Model), was calibrated and validated with field measurements, and used to determine the long-term effect of a winter wheat (Triticum aestivum L.) cover crop on soil nitrogen balance in an 80-yr (1938–2017) no-tillage and rainfed corn (Zea mays L.)–soybean (Glycine max L.) rotations in northeastern Mississippi, United States. Based on annual soil nitrogen dynamics, the model also estimated nitrate losses to deep percolation during wheat, corn, and soybean growth periods under different seasonal rainfall patterns. A record of seasonal rainfall for 80 consecutive years (1938–2017) was classified as ‘wet’, ‘normal’, ‘dry’ years using frequency analysis approach, and the classifications were matched chronologically to each of these three crop growth periods as model input parameters. Results showed that, mean annual net nitrogen mineralization and annual denitrification were respectively 15% and 9% higher under wheat cover crop (WCC) than under winter fallow (WF) across 80 simulation years. Average annual nitrate leaching was 20% less in the WCC than in the WF system (68.2 vs. 84.8 kg N ha−1). The difference in annual nitrate leaching between the two treatments is equivalent to 17% of the total fertilizer nitrogen-applied annually for corn-soybean system. Compared to WF, the WCC system during autumn to spring (early October to early April) reduced simulated annual nitrate leaching losses by 19.6, 18.6, and 8.2 kg N ha−1 in wet, normal, and dry years, respectively. Long-term integration of wheat cover crop into a no-till corn-soybean rotation is a promising agronomic practice for reducing nitrate leaching and also fertilizer-nitrogen input in the humid northeastern Mississippi, especially in wetter fallow seasons from early October to early April.

Cover Crops for Managing Stream Water Quantity and Improving Stream Water Quality of Non-Tile Drained Paired Watersheds

In the Midwestern United States, cover crops are being promoted as a best management practice for managing nutrient and sediment losses from agricultural fields through surface and subsurface water movement. To date, the water quality benefits of cover crops have been inferred primarily from plot scale studies. This project is one of the first to analyze the impacts of cover crops on stream water quality at the watershed scale. The objective of this research was to evaluate nitrogen, phosphorus, and sediment loss in stream water from a no-till corn-soybean rotation planted with winter cover crops cereal rye (Secale cereale) and hairy vetch (Vicia villosa) in non-tile drained paired watersheds in Illinois, USA. The paired watersheds are under mixed land use (agriculture, forest, and pasture). The control watershed had 27 ha of row-crop agriculture, and the treatment watershed had 42 ha of row crop agriculture with cover crop treatment (CC-treatment). During a 4-year calibration period, 42 storm events were collected and Event Mean Concentrations (EMCs) for each storm event were calculated for total suspended solids (TSS), nitrate-N (NO3-N), ammonia-N (NH4-N), dissolved reactive phosphorus (DRP), and total discharge. Predictive regression equations developed from the calibration period were used for calculating TSS, NO3-N, NH4-N, and DRP losses of surface runoff for the CC-treatment watershed. The treatment period consisted of total 18 storm events, seven of which were collected during the cereal rye, eight in the hairy vetch cover crop season and three during cash crop season. Cover crops reduced TSS and discharge by 33% and 34%, respectively in the CC-treatment watershed during the treatment period. However, surprisingly, EMCs for NO3-N, NH4-N, and DRP did not decrease. Stream discharge from the paired-watersheds will continue to be monitored to determine if the current water quality results hold or new patterns emerge.

Impacts of biosolids application on soil quality under alternate year no-till corn–soybean rotation

Biosolids are a source of recycled organic matter and nutrients. To evaluate the impact of biosolids application (1984-2008) on soil quality, composite soils (Genesee silt loam, fine loamy, mixed, nonacid, and mesic typic udifluvent) were randomly sampled at geo-referenced sites from 0 (control), 2, 5, and 25 years of lime-stabilized anaerobically digested biosolid- applied fields. Results showed that microbial biomass C( Cmic), N (Nmic), and P (Pmic) contents were signifi- cantly higher at both depths of the 5 and 25 years of biosolid-appliedfieldscomparedtothecontrol.Biosolid application significantly enlarged the biologically labile C( Cmic over total organic C, Cmic:Corg )a nd N( Nmic overtotalN,Nmic:TN)poolswithanassociateddecrease in metabolic C loss (20-53 %) by specific maintenance respiration (qCO2) relative to the control. The Corg, active (AC) and soluble C (SC), TN and reactive N (RN), and reactive P (RP) contents were significantly higher in the long-term biosolid-applied fields than in the control. However, there was an indication of leaching of SC, RN, and RP between depths. Years of biosolidapplicationsignificantlyincreasedsoilmoisture content (θv at −0.03 MPa) by 20-40 %, macroaggregate stability (MaA) by 2-44 %, and mean weight diameter (MWD) of aggregates by 7-51 %, respectively. Conse- quently, there was a decrease in soil bulk density (ρb) and microaggregate stability (MiA) at both depths. Re- sults confirmed that biosolids application at rates rec- ommended is a viable management option to improve soil quality for crop production. However, long-term and repeated biosolid applications above the recom- mended agronomic N and P rates may be responsible for accumulation and consequent leaching and runoff of SC,RN,and RP tocause groundwaterandsurface water pollution with environmental consequences.

Cover crops in the upper midwestern United States: Simulated effect on nitrate leaching with artificial drainage

A fall-planted winter cover crop is an agricultural management practice with multiple benefits that may include reducing nitrate (NO₃) losses from artificial drained agricultural fields. While the practice is commonly used in the southern and eastern United States, little is known about its efficacy in midwestern states where winters are longer and colder, and artificial subsurface drainage is widely used in corn–soybean systems (<i>Zea mays</i> L.–<i>Glycine max</i> L.). We used a field-tested version of the Root Zone Water Quality Model (RZWQM) to simulate the adoption of cereal rye (<i>Secale cereale</i> L.) as a winter cover crop and estimate its impact on NO₃ losses from drained fields at 41 sites across the Midwest from 1961 to 2005. The average annual nitrogen (N) loss reduction from adding winter rye ranged from 11.7 to 31.8 kg N ha⁻¹ (10.4 to 28.4 lb N ac⁻¹) among four simulated systems. One of the simulated treatments was winter rye overseeded (aerial seeded) into a no-till corn–soybean rotation at simulated main crop maturity (CC2). On average, this treatment reduced simulated N loss in drainage by 20.1 kg N ha⁻¹ (17.9 lb N ac⁻¹) over the sites compared to systems without winter rye (NCC2), from 47.3 to 27.2 kg N ha⁻¹ (42.2 to 24.3 lb N ac⁻¹). Adding spring tillage to this treatment and killing the rye earlier (CC3) reduced simulated N loss from 57.3 (NCC3) to 34.4 kg N ha⁻¹ (30.7 lb N ac⁻¹). Replacing the corn–soybean rotation with continuous corn and spring tillage reduced simulated N loss from 106 (NCC4) to 74.2 kg N ha⁻¹ (CC4) (94.6 to 66.2 lb N ac⁻¹). Adding a winter rye cover crop reduced N loss more in the continuous corn system despite earlier spring termination of the winter rye and slightly less N uptake by the rye possibly because of more denitrification. Regression analysis of the RZWQM variables from these sites showed that temperature and precipitation during winter rye growth, N fertilizer application rates to corn, and simulated corn yield account for greater than 95% of the simulated site-to-site variability in NO₃ loss reductions in tile flow due to winter rye. Our results suggest that on average winter rye can reduce N loss in drainage 42.5% across the Midwest. Greater N loss reductions were estimated from adding winter rye at sites with warmer temperatures and less precipitation because of more cover crop growth and more soil N available for cover crop uptake.

Biosolid Impact on Heavy Metal Accumulation and Lability in Soiln Under Alternate-Year No-Till Corn–Soybean Rotation

Biosolids are nutrient-rich waste products often used as soil amendments. To evaluate the impact of repeated application of biosolids on heavy metal accumulation and lability, composite soils (at 0–15- and 15–30-cm depths) were collected from 0-, 2-, 5-, and 25-year biosolid-applied Genesee silt loam (fine loamy, mixed, nonacid, mesic Typic Udifluvent). While the biosolid application did not influence the pH, the electrical conductivity and heavy metal concentration varied significantly. Among the heavy metals, the concentration of total and residual cadmium (Cd) was the highest (3 and 2.8 times), and copper (Cu) was the lowest (1.3 to 1.2 times) in the 25-year biosolid-applied field than in the control. The exchangeable chromium (Cr) concentration was the highest (6 times), and Cu was the lowest (1.9 times) in the 25-year biosolid-applied field as compared with the control. The lability of Cr, lead (Pb), cobalt (Co), zinc (Zn), Cu, nickel (Ni), and arsenic (As) significantly increased by 20, 11, 9, 9, 8, 6, and 4 %, respectively, in the 25-year biosolid-applied field compared to the control field. The extractable Pb, As, Zn, and Cu concentrations were significantly higher at 0–15 cm than at 15–30 cm depth. The labilities of Pb, Cu, and Ni were significantly varied between depths. Biosolids × depth significantly influenced the total As and residual As, Cu, and Pb concentrations. All the heavy metals except total and residual As significantly correlated with the total organic carbon. Results suggest that the accumulation and lability of heavy metals are related to complexation of heavy metals with organic carbon in response to years of biosolid application.

Contrasting grain crop and grassland management effects on soil quality properties for a north-central Missouri claypan soil landscape

Crop management has the potential to either enhance or degrade soil quality, which in turn impacts on crop production and the environment. Few studies have investigated how crop management affects soil quality over different landscape positions. The objective of the present study was to investigate how 12 years of annual cropping system (ACS) and conservation reserve program (CRP) practices impacted soil quality indicators at summit, backslope and footslope landscape positions of a claypan soil in north-central Missouri. Claypan soils are particularly poorly drained because of a restrictive high-clay subsoil layer and are vulnerable to high water erosion. Three replicates of four management systems were established in 1991 in a randomized complete block design, with landscape position as a split-block treatment. The management systems were investigated: (1) annual cropping system 1 (ACS1) was a mulch tillage (typically ≥ 30% of soil covered with residue after tillage operations) corn (Zea mays L.)–soybean (Glycine max (L.) Merr.) rotation system, (2) annual cropping system 2 (ACS2) was a no-till corn–soybean rotation system, (3) annual cropping system 3 (ACS3) was a no-till corn–soybean–wheat (Triticum aestivum L.) rotation system, with a cover crop following wheat, (4) CRP was a continuous cool-season grass and legume system. In 2002, soil cores (at depths of 0–7.5, 7.5–15 and 15–30 cm) were collected by landscape position and analyzed for physical, chemical and biological soil quality properties. No interactions were observed between landscape and crop management. Relative to management effects, soil organic carbon (SOC) significantly increased with 12 years of CRP management, but not with the other management systems. At the 0–7.5-cm soil depth in the CRP system, SOC increased over this period by 33% and soil total nitrogen storage increased by 34%. Soil aggregate stability was approximately 40% higher in the no-till management systems (ACS2 and ACS3) than in the tilled system (ACS1). Soil aggregation under CRP management was more than double that of the three grain-cropping systems. Soil bulk density at the shallow sampling depth was greater in ACS3 than in ACS1 and ACS2. In contrast to studies on other soil types, these results indicate only minor changes to claypan soil quality after 12 years of no-till management. The landscape had minor effects on the soil properties. Of note, SOC was significantly lower in the 7.5–15-cm soil depth at the footslope compared with the other landscape positions. We attribute this to wetter and more humid conditions at this position and extended periods of high microbial activity and SOC mineralization. We conclude that claypan soils degraded by historical cropping practices will benefit most from the adoption of CRP or CRP-like management.

Net Global Warming Potential and Greenhouse Gas Intensity in Irrigated Cropping Systems in Northeastern Colorado

The impact of management on global warming potential (GWP), crop production, and greenhouse gas intensity (GHGI) in irrigated agriculture is not well documented. A no-till (NT) cropping systems study initiated in 1999 to evaluate soil organic carbon (SOC) sequestration potential in irrigated agriculture was used in this study to make trace gas flux measurements for 3 yr to facilitate a complete greenhouse gas accounting of GWP and GHGI. Fluxes of CO2, CH4, and N2O were measured using static, vented chambers, one to three times per week, year round, from April 2002 through October 2004 within conventional-till continuous corn (CT-CC) and NT continuous corn (NT-CC) plots and in NT corn-soybean rotation (NT-CB) plots. Nitrogen fertilizer rates ranged from 0 to 224 kg N ha(-1). Methane fluxes were small and did not differ between tillage systems. Nitrous oxide fluxes increased linearly with increasing N fertilizer rate each year, but emission rates varied with years. Carbon dioxide efflux was higher in CT compared to NT in 2002 but was not different by tillage in 2003 or 2004. Based on soil respiration and residue C inputs, NT soils were net sinks of GWP when adequate fertilizer was added to maintain crop production. The CT soils were smaller net sinks for GWP than NT soils. The determinant for the net GWP relationship was a balance between soil respiration and N2O emissions. Based on soil C sequestration, only NT soils were net sinks for GWP. Both estimates of GWP and GHGI indicate that when appropriate crop production levels are achieved, net CO2 emissions are reduced. The results suggest that economic viability and environmental conservation can be achieved by minimizing tillage and utilizing appropriate levels of fertilizer.

EXPERIMENTAL EVALUATION OF INFILTRATION MODELS FOR DIFFERENT LAND USE AND SOIL MANAGEMENT SYSTEMS

Soil structural and water transmission properties, as influenced by land use and soil management, affect the coefficients of infiltration predictive models. Ten infiltration models were analyzed to assess these coefficients. The models tested include Green and Ampt (1911), Kostiakov (1932), Horton (1940), Mezencev (1948), Philip (1957), Holtan (1961)-two and three-parameters, Stroosnijder (1976), Swartzendruber (1987), and Kutilek and Krejca (1987). Parameters were evaluated for time-dependence and precision and with regard to the effects of land use/soil management and landscape positions. The field water infiltration data used in these models were based on double ring infiltrometer tests conducted for 3 h at six different land use/soil management treatments at the North Appalachian Experimental Watersheds (NAEW) near Coshocton, Ohio. The treatments were no-till without manure (NTWM), no-till with manure (NTM), no-till corn-soybean rotation (NTCSR), conventional tillage (CT), meadow (M) and forest. Measurements were made at three landscape positions (e.g., shoulder or upper slope (US); back or middle slope, (MS); and foot slope (FS)). The algebraic parameters of the infiltration models and nonlinear least squares regression were fitted using measured infiltration time [I (t)] data. Among process-based infiltration models, the Swartzendruber model performed best and matched the measured I (t) data with lower sum of squares (SS) and higher model efficiency (EF) and Wilmot's index of agreement (W). Overall the three-parameter Horton model gave the best representation of the I (t) relationship with the lowest SS and the highest EF and W for most of the land use treatments, including forest. The treatments had significant influence on the parameters related to initial infiltration rate or sorptivity and final steady state infiltration rate or hydraulic conductivity near saturation, whereas landscape positions had significant influence on the sorptivity parameter only. The fitted parameters (i.e., sorptivity and hydraulic conductivity near saturation) were time dependent and were higher for NTM than for other treatments.