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Crop rotations in the northern Great Plains of North America increasingly include corn (Zea mays L.) and soybean (Glycine max (L.) Merr.). Use of cover crops, while less extensive, is also increasing given their purported agronomic and environmental benefits. To date, soil responses to the inclusion of corn, soybean, and cover crops in rainfed cropping systems have not been well documented in the region. Therefore, soil properties were evaluated 6 years after establishment of three crop rotations (spring wheat (Triticum aestivum L.)–soybean (SW–S), spring wheat–corn–soybean (SW–C–S), and spring wheat–corn–cover crop (SW–C–cc)) each split by no and minimum tillage on a Dark Brown Chernozem near Mandan, ND, USA. Soil responses to treatments were subtle and exclusive to the 0–7.6 cm depth. Soil pH was lower in SW–S than SW–C–cc (5.28 vs. 5.48; P = 0.05), SO4-S was greater under SW–C–cc than SW–C–S (13.4 vs. 11.6 g S kg−1; P = 0.03), exchangeable K was greater under SW–C–S and SW–C–cc than SW–S (0.83 cmol kg−1 vs. 0.52 cmol kg−1; P = 0.05), and water-stable aggregates were greater in SW–S than SW–C–S (26% vs. 19%; P = 0.08). Soil organic carbon (SOC) and total N did not differ among crop rotations or between tillage treatments, while particulate organic matter N was greater under no tillage compared to minimum tillage (P = 0.08). Between 2012 and 2018, soil pH decreased and SOC increased under SW–C–S. Frequent monitoring of near-surface soil conditions in rotations with soybean every other year is recommended. Furthermore, innovative management practices are needed to enhance soil C and N fractions in rotations with full-season cover crops. [ABSTRACT FROM AUTHOR]

Conservation agriculture is often assumed to reduce soil N2O emissions. Yet, studies analyzing the specific effect of conservation agriculture practices on N2O emissions give contradictory results. Herein, we synthesized a comprehensive database on the three main conservation agriculture practices (cover crops, diversified crop rotations, and no-till and/or reduced tillage (NT/RT)) to elucidate the role of conservation practices on N2O emissions. Further, we used a random meta-forest approach to identify the most important predictors of the effects of these practices on soil N2O emissions. Averaged across all comparisons, NT/RT significantly decreased soil N2O emissions by 11% (95% CI: –19 to –1%) compared to conventional tillage. The reductions due to NT/RT were more commonly observed in humid climates and in soils with an initial carbon content < 20 g kg–1. The implementation of cover crops and diversified crop rotations led to variable effects on soil N2O emissions. Cover crops were more likely to reduce soil N2O emissions at neutral soil pH, and in soils with intermediate carbon (~20 g kg–1) and nitrogen (~3 g kg–1) contents. Diversified crop rotations tended to increase soil N2O emissions in temperate regions and neutral to alkaline soils. Our results provide a comprehensive predictive framework to understand the conditions in which the adoption of various conservation agriculture practices can contribute to climate change mitigation. Combining these results with a similar mechanistic understanding of conservation agriculture impacts on ecosystem services and crop production will pave the way for a wider adoption globally of these management practices. [ABSTRACT FROM AUTHOR]

Integrated crop–livestock (ICL) systems have shown potential to provide a variety of environmental benefits including soil carbon (C) increases relative to conventional row cropping systems. However, studies documenting C dynamics of ICL systems in the northern Great Plains are lacking relative to other agroecosystems. Soil carbon dioxide (CO2) efflux, crop biomass, and soil organic matter (SOM) pools were monitored over 3 years in an ICL rotation (corn [Zea mays L.]/soybean [Glycine max L.]–spring wheat [Triticum aestivum L.] + cover crop–cover crop) with fall grazing, a conventional cropping system rotation (corn–spring wheat–soybean) and fall grazed and ungrazed mixed‐grass pasture near Mandan, ND. Cropped treatments were under no‐till management. Annual aboveground crop residue biomass C was similar in the ICL and conventional systems, while less in the grazed pasture (4.18, 3.83, and 1.21 Mg C ha−1 year−1 respectively; p = 0.039). Annual soil CO2 efflux was greater in the ICL, grazed, and ungrazed pasture systems than the conventional system (8.05, 8.73, 8.25, and 5.81 Mg C ha−1 year−1, respectively; p < 0.001). Among crop phases in the ICL and conventional cropping systems, cover crops contributed to greater CO2 efflux in the spring and fall. SOM and C mineralization were greater at 0–5 cm in the ICL system compared to the conventional cropping system (6.6% vs. 6.3%, p = 0.028 and 248 vs. 184 mg CO2–C kg−1, p < 0.001, respectively). Interseeded cover crops in ICL systems can contribute increased root respiration and enhanced SOM pools relative to conventional cropping systems under semiarid conditions. Core Ideas: Soil carbon (C) dynamics in integrated crop–livestock (ICL) systems are not well understood.Soil carbon dioxide (CO2) efflux and labile pools of soil organic matter (SOM) were evaluated over 3 years.Soil CO2 efflux was greater in the ICL system compared to conventional cropping.SOM and C mineralization were also greater in the ICL system compared to conventional cropping.Interseeded cover crops in ICL systems can enhance soil C pools and biological activity. [ABSTRACT FROM AUTHOR]

Interest in cover crops is increasing but information is limited on integrating them into crop rotations especially in the relatively short growing season on the northern Great Plains. A 3-yr research project, initiated in 2009 near Mandan, North Dakota, USA, evaluated (1) what impact cover crops may have on subsequent cash crops yields and (2) whether cover crop mixtures are more productive and provide additional benefits compared to cover crop monocultures. The study evaluated 18 different cover crop monocultures and mixtures that were seeded in August following dry pea (Pisum sativum L.). The following year, spring wheat (Triticum aestivum L.), corn (Zea mays L.), soybean (Glycine max L.) and field pea were seeded into the different cover crop treatments and a non-treated control. A lack of timely precipitation in 2009 resulted in a low cover crop yield of 17 g m2 compared to 100 and 77 g m2 in 2008 and 2010, respectively. Subsequent cash crop yield was not affected by late-seeded cover crops. Cool-season cover crop monocultures were more productive than warm-season monocultures and some mixtures in 2008 and 2010. Relative yield total did not differ from one in any cover crop mixture suggesting that overyielding did not occur. Species selection rather than species diversity was the most important contributor to cover crop yield. Cover crops can be grown following short-season cash crops in the northern Great Plains, but precipitation timing and species selection are critical. [ABSTRACT FROM AUTHOR]

Many integrated crop-livestock system (ICL) studies have been conducted, but few report cattle performance and forage nutrients. Here, we report one year of cattle weight gains for Angus yearling heifers and steers grazing ICL plots (ICL) or tame grass pastures (PAS) in four replicates. Five yearlings (avg. BW 390 ± 26 kg) were randomly assigned to graze each plot while provided ad libitum water and trace mineral salt. Cattle assigned to ICL grazed three crop rotations: 1) corn interseeded with soybean (C/S), 2) spring wheat interseeded with cover crop and 3) cover crop planted into spring wheat from the previous year. Yearlings in ICL were stocked first on green C/S, grazing an average of 60 days. Beginning C/S biomass was 1,827 ± 638 g m-2, yearling end BW was 465 ± 34 kg and ADG 1.28 ± 0.27 kg. Yearlings then grazed residual cover crop growth, averaging additional 42 d grazing while supplemented with a ration of baled cover crop forage, wheat straw, and corn. Ration intake averaged 15.35 ±0.6 kg animal-1 d-1. Final BW of ICL yearlings on cover crops averaged 499 ± 34 kg, ADG of 0.79 ± 0.29 kg. Yearlings assigned PAS were provided 1,911 ± 162 g m-2 at the beginning of grazing for 69 days, had final BW 443 ± 35 kg, ADG of 1.01 ± 0.22. Forage nutrient analyses are reported in Table 1, showing that individual crops are similar in ADF and TDN, but vary in crude protein content. Performance of ICL cattle exceeded that of PAS while on corn and soybean but decreased ICL performance while grazing cover crop was likely due to extreme cold weather at the time of grazing. Nutrient values reported here can be used to plan and predict cattle growth while grazing crop residues instead of pastures. [ABSTRACT FROM AUTHOR]

Cropland agriculture in the northern Great Plains is challenged by variable weather, agricultural intensification, and competing use for energy development. Innovative cropland practices that address these challenges are needed to ensure regional agriculture can sustainably meet future food, fuel, and fiber demand. In response to this need, the Northern Plains Long-Term Agroecosystem Research Network site established a cropland experiment in 2019 that contrasts prevailing and alternative practices at plot and field scales over a proposed 30-year time frame. The experimental site is located on the Area IV Soil Conservation Districts Cooperative Research Farm near Mandan, ND. Cropping practices for the first 6 years of the experiment were developed with input from stakeholders and include a 3-year crop rotation of spring wheat (Triticum aestivum L.), corn (Zea mays L.), and soybean (Glycine max L.) with cover crops (alternative practice) and without (prevailing practice). The prevailing practice also involves the removal of crop residue, while a second alternative practice of perennial forages is included in the plot-scale experiment. Biophysical measurements are made at both spatial scales at frequencies aligned with approved methods for each agronomic and environmental metric. Findings from the first 6 years of the experiment will help identify tradeoffs associated with cover crop use and residue removal in dryland cropping systems. In the future, the experiment will adopt a knowledge co-production approach whereby researchers and stakeholders will work collaboratively to identify problems, implement research, and interpret results., (© 2024 The Authors. Journal of Environmental Quality published by Wiley Periodicals LLC on behalf of American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.)