Core Ideas We studied the impact of three rotations and two tillage systems on soil biological health after 25 yr. A significant rotation × tillage interaction was found for microbial biomass C and N, hot‐water‐extractable C, and urease and β‐glucosidase activity. Adoption of no‐till and diversified crops improved these soil health properties. Crop rotational diversity and tillage management influence soil microbial properties. Three crop rotations [maize (Zea mays L.)–soybean (Glycine max [Merr.] L.) (the 2‐yr rotation); maize–soybean–oat (Avena sativa L.) (3‐yr rotation); maize–soybean–oat–wheat (Triticum aestivum L.) (4‐yr rotation)] in combination with no‐till (NT) and conventional tillage (CT) were used to assess the impact on soil health parameters such as microbial biomass C (MBC) and microbial biomass N (MBN), C fractions, and urease and β‐glucosidase enzymes. Soil samples were collected in the maize and soybean phases at planting and harvest in 2016 at surface depth (0–7.5 cm). A significant tillage × rotation interaction was observed for all the parameters. At planting, under the maize phase, NT with the 4‐yr rotation increased MBC by 86% and MBN by 20% compared with the same cropping system (4‐yr) under CT. The hot‐water‐extractable C fraction under NT was, respectively, 19, 27, and 71% higher at maize harvest, soybean planting, and soybean harvest than under CT. Urease activity under the 4‐yr rotation with NT was 55% higher than that under the 2‐yr rotation with NT and almost doubled that under the 4‐yr rotation with CT. Beta‐glucosidase enzyme activity was higher under the 2‐yr cropping system with NT than in the other treatments at planting and harvest in the maize phase. A diverse cropping system (maize–soybean–wheat–oat, the 4‐yr rotation) managed with NT could benefit soil health by improving MBC, MBN, hot‐water‐extractable C, and urease and β‐glucosidase enzyme activity.
Diversification within a cropping system together with no-till (NT) soil management can help to improve soil organic carbon (SOC). The present study was conducted to assess the impacts of crop diversity through crop rotations on SOC and other selected soil properties. The long-term experimental sites were located in Beresford and Brookings, South Dakota, USA. The Beresford site was initiated in 1991 (24 years) on Egan soil series (fine-silty, mixed, superactive, mesic Udic Haplustolls), whereas, the Brookings site was established in 2000 (14 years) on a Barnes clay loam soil (fine-loamy, mixed, superactive, frigid Calcic Hapludolls) under a randomised complete block design with four replications. Treatments at both sites consisted of a 2-year (corn (Zea mays L.)–soybean (Glycine max L.)), and a 4-year (corn–soybean–winter wheat (Triticum aestivum L.)–oat (Avena sativa L.)) rotation, all managed under NT soil management. Soil samples were collected in the fall of 2015 after crop harvest under the corn phase. Data showed that 4-year rotation increased SOC stock (8.3% in Brookings and 22% in Beresford) compared with that under 2-year rotation (not always significant) in the soil profile 0–60cm. Soil particulate organic matter and organic matter were always higher under 4-year rotation than under 2-year rotation at 0–5 and 5–15cm depths at both sites. Surface soil aggregate stability was improved in both locations under 4-year rotation (12% in Brookings, 4% in Beresford). Additionally, at 0–5cm depth, the 4-year rotation increased light fractions of carbon (18% in Brookings, and 32% in Beresford) compared with 2-year. Results from this study showed that the use of diverse crop rotations (4-year) for longer (>24 years) duration enhanced SOC, carbon and nitrogen fractions, and soil aggregation compared with those under corn–soybean (2-year) rotation.
Prairie cordgrass (PCG) (Spartina pectinata Link) has a high tolerance to soil salinity and waterlogging, therefore, it can thrive on marginal lands. Optimizing the nitrogen (N) input is crucial to achieving desirable biomass production of PCG without negatively impacting the environment. Thus, this study was based on the hypothesis that the use of legumes such as kura clover (Trifolium ambiguum M. Bieb.) (KC) as an intercrop with PCG can provide extra N to the crop reducing the additional N fertilizer and mitigating soil surface greenhouse gas (GHG) emissions. Specific objective of the study was to assess the impact of PCG managed with different N rates [0 kg N ha−1 (PCG-0N), 75 kg N ha−1 (PCG-75N), 150 kg N ha−1 (PCG-150N), and 225 kg N ha−1 (PCG-255N)], and PCG intercropped with KC (PCG-KC) on GHG fluxes and biomass yield. The experimental site was established in 2010 in South Dakota under a marginally yielding cropland. The GHG fluxes were measured from 2014 through 2018 growing seasons using the static chamber. Net global warming potential (GWP) was calculated. Data showed that cumulative CH4 and CO2 fluxes were similar for all the treatments over the study period. However, the PCG-KC, PCG-0N, and PCG-75N recorded lower cumulative N2O fluxes (384, 402, and 499 g N ha−1, respectively) than the PCG-150N (644 g N ha−1) and PCG-255N (697 g N ha−1). The PCG-KC produced 85% and 39% higher yield than the PCG-0N in 2016 and 2017, respectively, and similar yield to the other treatments (PCG-75N, PCG-150N, and PCG-255N) in these years. Net GWP was 52% lower for the PCG-KC (112.38 kg CO2-eq ha−1) compared to the PCG-225N (227.78 kg CO2-eq ha−1), but similar to other treatments. Soil total N was 15%% and 13% higher under PCG-KC (3.7 g kg−1) than that under PCG-0N (3.2 g kg−1) and PCG-75N (3.3 g kg−1), respectively. This study concludes that intercropping prairie cordgrass with kura clover can enhance biomass yield and reduce fertilizer-derived N2O emissions and net global warming potential.
This study examined the effect of crop rotations and winter cover crops (CCs) on near‐surface pore characteristics of a silty clay loam soil in a 27‐yr no‐till field experiment. The crop rotation treatments included a 2‐yr corn (Zea mays L.)–soybean [Glycine max L. (Merr.)] (CS) rotation and a 4‐yr corn–soybean–oat (Avena sativa L.)–winter wheat (Triticum aestivum L.) (CSOW) rotation. The subplot treatment was CC and no‐CC (fallow). Intact soil cores (7.62 by 7.62 cm) were extracted from each treatment in July 2018 from soybean plots and examined for X‐ray computed tomography (CT)‐measured pore parameters and other soil physical and hydrological properties. Data showed that, compared with fallow, the CC reduced bulk density (ρb) by 6% and increased saturated hydraulic conductivity (Ksat) and water infiltration rate (qs) by 1.5 times. Soils under CSOW rotation had 16, 14, and 4% higher values of soil organic carbon (SOC), total nitrogen (TN), and wet aggregate stability (WAS) compared with those under CS rotation, respectively. The CSOW rotation significantly (P < .05) increased number of CT‐measured pores, number of macropores (>1,000 μm diameter), coarse mesopores (226–1,000 μm diameter), macroporosity, and mesoporosity compared with the CS system. The CT‐measured total porosity, number of macropores, and macroporosity were 43, 34, and 60%, respectively, higher with CC as compared to the fallow plots. The CT‐measured pore parameters were well correlated with soil ρb, Ksat, qs, SOC, TN, and WAS. This study emphasizes that cropping systems that include diverse crop rotations (CSOW) and CC has potential to enhance SOC, pore characteristics, and associated physical and hydrological properties.
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