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Diverse patterns of climate and edaphic factors challenge detection of soil property change in the US Great Plains. Because detectable soil change can take decades, insights into the trajectory of soil properties frequently require long‐term site monitoring and, where available, associated soil archives to enable comparisons with initial or baseline states. Unfortunately, few multi‐decadal soil change investigations have been conducted in this region. Here, we document effects of dryland cropping on a suite of soil properties by comparing matched historic (1947) and contemporary (2018) soil samples from the Haas Soil Archive at three sites in the US Great Plains: Moccasin, MT, Akron, CO, and Big Spring, TX. Current analytical methods were used to provide insight into changes in soil texture, pH, carbon, and micronutrients at 0‐ to 15.2‐cm and 15.2‐ to 30.5‐cm depths. Changes in direction and magnitude of soil properties over 71 years were site specific. Changes in textural class occurred at all sites, with Moccasin and Akron transitioning from loam to clay loam and Big Spring from sandy clay loam to sandy loam. The soil pH reaction class changed from slightly alkaline to moderately acid at Akron and slightly alkaline to moderately alkaline at Big Spring. At 0–15.2 cm, soil organic carbon decreased by 15% and 36% at Moccasin and Big Spring, respectively, but increased by 15% at Akron. Soil micronutrients generally declined at all sites. Weather‐related variables derived from air temperature and precipitation records were not correlated with soil change. Inferred factors contributing to soil change included on‐site management, inherent soil features, weather metrics not evaluated, or a combination thereof. Core Ideas: Soil change under dryland cropping was documented over 71 years in the US Great Plains.Changes in the direction and magnitude of texture, pH, and soil organic carbon were site specific.Soil micronutrients generally declined at all sites.Soil archives are essential for documenting long‐term soil change. [ABSTRACT FROM AUTHOR]

Wind erosion and variable weather challenge crop production in the northern Great Plains. Management that increases residue cover might mitigate wind erosion during the cash crop growing season. We evaluated horizontal sediment flux (modified Wilson and Cooke samplers) and cash crop yield across a single rotation of corn (Zea mays L.)–soybean (Glycine max (L.) Merr.)–spring wheat (Triticum aestivum L.) in paired fields with contrasting management. One field included cover crops and retained spring wheat straw (aspirational), while the other excluded both conservation practices over the 3‐year rotation (business‐as‐usual). Horizontal sediment flux rapidly decreased with days after cash crop planting (increasing crop canopy), regardless of management treatment. In 2 years (2020 corn and 2022 spring wheat), there was greater horizontal sediment flux, lower cash crop grain yield, and lower cash crop aboveground biomass in the aspirational versus business‐as‐usual field. In 2021 soybean, there was lower horizontal sediment flux, greater cash crop yield, and greater cash crop aboveground biomass in the aspirational versus business‐as‐usual field. Higher yield and lower horizontal sediment flux responses corresponded with the management treatment that produced the higher cash crop aboveground biomass. Additionally, our short‐term study indicated that in drought years, cover crops worsened the adverse effects of abnormally low precipitation on yield and biomass of 2020 corn but not 2021 soybean. Core Ideas: Sediment mass flux and grain yield were measured in response to cover cropping and wheat straw management.Horizontal sediment flux rapidly decreased with canopy development, regardless of management treatment.During drought, cover crops decreased yield and biomass of corn but not soybean.Conservation practices treatment had lower horizontal sediment flux in 2021 soybean, but not in 2020 or 2022. [ABSTRACT FROM AUTHOR]

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]

Understanding controls on soil organic carbon (SOC) will be crucial to managing soils for climate change mitigation and food security. Climate exerts an overarching influence on SOC, affecting both carbon (C) inputs to soil and soil physicochemical properties participating in C retention. To test our hypothesis that climate, C inputs, and soil properties would differently affect particulate organic carbon (POC) and mineral-associated organic carbon (MAOC), we sampled 16 agricultural sites (n = 124 plots) in the United States, ranging in climate (mean annual precipitation (MAP)—potential evapotranspiration (PET; MAP-PET)), soil pH (5.8–7.9), and soil texture (silt + clay = 13–96%). As MAP-PET increased, soils increased in oxalate-extractable iron (FeO) and aluminum (AlO), decreased in exchangeable calcium (Caex) and magnesium (Mgex), and received greater C inputs. Soil physicochemical properties did not strongly predict POC, confirming the relative independence of this SOC fraction from the soil matrix. In contrast, MAOC was well predicted by combining AlO + [1/2]FeO with Caex + Mgex in a 'matrix capacity index', which performed better than individual soil physicochemical properties across all pH levels (r > 0.79). Structural equation modeling indicated a similar total effect of MAP-PET on MAOC and POC, which was mediated by total C inputs and the matrix capacity index for MAOC but not POC. Our results emphasize the need to separately conceptualize controls on MAOC and POC and justify the use of a unified soil matrix capacity index for predicting soil MAOC storage. [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]

Farmers and ranchers depend on annual forage production for grassland livestock enterprises. Many regression and machine learning (ML) prediction models have been developed to understand the seasonal variability in grass and forage production, improve management practices, and adjust stocking rates. Moreover, decision support tools help farmers compare management practices and develop forecast scenarios. Although numerous individual studies on forage growth, modeling, prediction, economics, and related tools are available, these technologies have not been comprehensively reviewed. Therefore, a systematic literature review was performed to synthesize current knowledge, identify research gaps, and inform stakeholders. Input features (vegetation index [VI], climate, and soil parameters), models (regression and ML), relevant tools, and economic factors related to grass and forage production were analyzed. Among 85 peer-reviewed manuscripts selected, Moderating Resolution Imaging Spectrometer for remote sensing satellite platforms and normalized difference vegetation index (NDVI), precipitation, and soil moisture for input features were most frequently used. Among ML models, the random forest model was the most widely used for estimating grass and forage yield. Four existing tools used inputs of precipitation, evapotranspiration, and NDVI for large spatial-scale prediction and monitoring of grass and forage dynamics. Most tools available for forage economic analysis were spreadsheet-based and focused on alfalfa. Available studies mostly used coarse spatial resolution satellites and VI or climate features for larger-scale yield prediction. Therefore, further studies should evaluate the use of high-resolution satellites; VI and climate features; advanced ML models; field-specific prediction tools; and interactive, user-friendly, web-based tools and smartphone applications in this field. [ABSTRACT FROM AUTHOR]

Over the past 30 years, agricultural land use in the northern Great Plains has negatively affected soil health and associated ecosystem services through grassland conversion to cropland and a transition away from small‐grain cropping systems to warm‐season crops. Mitigating these effects requires adoption of conservation practices, but information about how conservation practices influence on soil condition and function are needed. This study sought to quantify near‐surface soil responses to crop diversity and intensity, cover crops, and livestock integration under controlled experimental conditions, and land use (dryland cropping vs. perennial agroecosystems) on working farms and ranches, all on a common Haplustoll soil in southcentral North Dakota, USA. Among dryland cropping practices, diverse, continuous cropping led to improvements in soil structure, nutrient supply potential, and biological habitat, but increased soil acidification and soil NO3–N accumulation. Cover crops had a negligible effect on soil condition and function, while livestock integration on cropland improved nutrient supply potential and biological habitat but impaired water intake into soil. Relative to dryland cropping, soil conditions and functions were consistently improved under perennial agroecosystems. Retention of perennial agroecosystems and adoption of diverse, nutrient‐efficient dryland cropping practices should be prioritized to enhance soil health in the northern Great Plains. Core Ideas: Conservation practices on croplands are needed in the northern Great Plains.Soil assessments were conducted on long‐term experiments and on‐farm research sites.Soil functions under cropland were impaired compared with perennial agroecosystems.Increased crop diversity and intensity improved soil quality indices and grain yield.Cropland conservation practices can create tradeoffs in soil function. [ABSTRACT FROM AUTHOR]

During periods of no or low crop growth in dryland cropping systems, tillage can reduce residue coverage and thereby elevate wind erosion risk. We measured wind erosion on a silt loam, Haplustoll soil in North Dakota (456 mm precipitation yr–1) in response to levels of tillage applied once in spring during fallow following a small grain–sunflower (Helianthus annuus L.) rotation. Treatments were no‐tillage (NT), one‐pass tandem disk tillage (TDT), and two‐pass offset disk tillage (ODT). Erosion flux was measured with sediment samplers near peripheries of >1‐ha replicated plots from May through September 2003 and 2004. Soil losses in ODT, TDT, and NT were 12.0, 4.8, and 2.1 Mg ha–1, respectively, in 2003 and 2.6, 1.6, and 1.4 Mg ha–1 in 2004. The greatest loss, 12.0 Mg ha–1, was equivalent to 1‐mm soil depth. The two‐ to fivefold greater erosion in 2003, a year with 2 mo of <30% of average precipitation, appears linked to a decline in residue coverage. Coverage remained about the same in NT and increased in tilled treatments during 2004 with more average precipitation. Our measurements of wind erosion have shown how the residue‐destroying effects of a single tillage event can be considerably exacerbated by a moderate, seasonal drought. This indicates the critical importance of NT for limiting soil and residue disturbance and reducing wind erosion risk from drought‐affected plant growth failure in semiarid cropping systems. Core Ideas: Wind erosion loss was two‐ to sixfold greater under disk tillage than no‐tillage.Seasonal drought led to less weed growth and residue coverage.Seasonal drought resulted in two‐ to fivefold greater wind erosion loss.The Revised Wind Erosion Equation (RWEQ) model indicated that residue coverage conferred the greatest resistance to erosion. [ABSTRACT FROM AUTHOR]

The increase in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] production in rainfed cropping systems of the northern Great Plains (NGP) has altered the delivery of ecosystem services from agricultural land. To date, there is limited understanding about how these crops affect the carbon (C) balance of cropping systems in the region when included in a short rotation window. This study sought to quantify C balance of a spring wheat (Triticum aestivum L.)–corn—soybean rotation under no‐tillage management using eddy covariance (EC) techniques. Paired field sites with the same soil type near Mandan, ND, were used for the study. Annual net ecosystem production (NEP) by crop was –34, 120, and 7 g C m–2 y–1 for spring wheat, corn, and soybean, respectively. Carbon removed in grain over the rotation was less than a third of C lost by ecosystem respiration (ER) (210 vs. 674 g C m–2 y–1). After accounting for grain C removal, net ecosystem carbon balance (NECB) was –164, –253, and –121 g m–2 y–1 for spring wheat, corn, and soybean, respectively, with a mean NECB of –179 ± 39 g C m–2 y–1 (P =.043; t test for difference from zero), implying the rotation was a net C source. Time associated with active crop growth each year was 27% for spring wheat, 41% for corn, and 28% for soybean. Management strategies that lengthen the period of biomass growth may mitigate C loss from spring wheat–corn–soybean rotations in the NGP. Core Ideas: Eddy covariance methods were used to quantify CO2 fluxes from a wheat–corn–soybean rotation. Annual net ecosystem production was negative for wheat, positive for corn, and near zero for soybean.Carbon removed in grain was less than a third of carbon lost by ecosystem respiration.Net ecosystem carbon balance for the rotation was negative, implying carbon loss. [ABSTRACT FROM AUTHOR]

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Soil archives preserve a snapshot of soils from a specific time and location, allowing researchers to re‐evaluate soils of the past in the context of the present for an improved understanding of long‐term soil change. To date, the extent of soil archive use in the peer‐reviewed literature is poorly inventoried. Here, we document the characteristics and distribution of global soil archive use, as found in 245 publications, following an exhaustive search of English language journals. Soil archive use has increased substantially since 1980, reaching 59 publications between 2016 and 2020. The age of soil archives across the compilation ranged from 5 to 160 yr, with mean and median archive ages of 48 and 37 yr, respectively. Publications using soil archives originated mostly from countries in the northern hemisphere, with the top five reporting countries including the United States (61), United Kingdom (52), New Zealand (21), Canada (18), and China (14). Land uses associated with soil archive publications were dominated by agroecosystems, specifically land planted to annual crops. Forty‐seven percent of investigations focused on changes in soil C, N, or organic matter, whereas investigations of other subjects did not exceed 20% each. The compilation is publicly available online. As demands on soils increase, archives will serve as an invaluable tool for understanding long‐term soil change in the Anthropocene era. Multiregional coordination and increased investment in curation and retention of soil archives are recommended to preserve these irreplaceable resources. Core Ideas: Archived soil samples facilitate an improved understanding of long‐term soil change.A literature review was conducted to compile metadata documenting soil archive use.Since 1980, there has been an accelerating use of soil archives in research.Research is primarily focused on soil organic matter change in agroecosystems.Resources are needed to support soil archives, especially in developing countries. [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]

Agricultural land management may influence crop nutritional quality. However, few studies have explored potential connections between crop quality with different land management strategies. We analyzed mineral and crude protein concentrations in spring wheat grain (Triticum aestivum L.) samples from a study in Mandan, ND conducted from 2006 to 2014. The study introduced a perennial forage phase into an annual spring wheat cropping system, in three to four replicates, and previously found yield benefits and enhanced soil parameters in the perennial forage treatments. We determined whether integrating a perennial forage phase into continuous wheat would also affect crop nutritional quality by measuring wheat grain mineral and protein concentrations. Crude protein concentration was greater (p <.05) when wheat followed alfalfa (Medicago sativa L.) and increased linearly after 2–5 yr of established alfalfa. We observed comparable wheat grain crude protein and mineral concentrations between continuous annually fertilized wheat and unfertilized wheat following perennial forages. Negative correlations (p <.001) were observed between wheat grain yield and crude protein, potassium (K), magnesium (Mg), nickel (Ni), phosphorus (P), sulfur (S), and zinc (Zn) concentrations. Discriminate multivariate analyses showed, with 96% predictive accuracy, that differences in crude protein and mineral concentration were largely driven by year of wheat harvest. Differences between harvest years were likely due to timely precipitation at critical Growth Stage 3, during spikelet development. Study outcomes highlighted the important role of perennial forages and environmental factors to influence protein and mineral concentration in spring wheat grain. Core Ideas: Perennial forages benefit annual cropping systems. Wheat grain samples were analyzed for mineral and protein concentration. Protein was greater when wheat followed alfalfa versus intermediate wheatgrass. Grain quality was similar between annual cropping and wheat following perennials. Grain mineral and protein concentrations were influenced by environmental factors. [ABSTRACT FROM AUTHOR]

Wheat (Triticum spp.) dominates dryland grain crop production in the North American Great Plains and other regions with semi‐arid steppe climates. A common practice is to alternate winter or spring wheat with a 14‐ to 21‐mo fallow period to allow for soil‐water recharge, despite economic inefficiencies and environmental degradation. Replacing fallow with non‐cereal grain and seed crops often reduces future wheat yields due to increased water stress during grain fill. The use of annual forages may not have the disadvantages associated with grain and seed crops. The objective of this review was to determine benefits and challenges of incorporating annual forages into dryland wheat systems in semi‐arid steppe climates, using the Great Plains within the United States as a model system. Results indicate that: (a) cool‐ and warm‐season, annual grass and broadleaf species can be grown for forage across the region; (b) forage production will be less risky than grain and seed crop production under predicted climate‐change scenarios; (c) grazing annual forages may offer advantages (e.g., nutrient cycling, improved soil structure, added revenue from livestock) over mechanically harvesting annual forages; (d) the lack of infrastructure and local markets impede the use of annual forages to diversify wheat‐based cropping systems in the region; and (e) limited networking among researchers hinders the advancement in knowledge on how annual forages can be used to improve dryland wheat system resilience. [ABSTRACT FROM AUTHOR]

A potential strategy for mitigating nitrous oxide (N2O) emissions from permanent grasslands is the partial substitution of fertilizer nitrogen (Nfert) with symbiotically fixed nitrogen (Nsymb) from legumes. The input of Nsymb reduces the energy costs of producing fertilizer and provides a supply of nitrogen (N) for plants that is more synchronous to plant demand than occasional fertilizer applications. Legumes have been promoted as a potential N2O mitigation strategy for grasslands, but evidence to support their efficacy is limited, partly due to the difficulty in conducting experiments across the large range of potential combinations of legume proportions and fertilizer N inputs. These experimental constraints can be overcome by biogeochemical models that can vary legume‐fertilizer combinations and subsequently aid the design of targeted experiments. Using two variants each of two biogeochemical models (APSIM and DayCent), we tested the N2O mitigation potential and productivity of full factorial combinations of legume proportions and fertilizer rates for five temperate grassland sites across the globe. Both models showed that replacing fertilizer with legumes reduced N2O emissions without reducing productivity across a broad range of legume‐fertilizer combinations. Although the models were consistent with the relative changes of N2O emissions compared to the baseline scenario (200 kg N ha−1 yr−1; no legumes), they predicted different levels of absolute N2O emissions and thus also of absolute N2O emission reductions; both were greater in DayCent than in APSIM. We recommend confirming these results with experimental studies assessing the effect of clover proportions in the range 30–50% and ≤150 kg N ha−1 yr−1 input as these were identified as best‐bet climate smart agricultural practices. Key Points: A partial substitution of fertilizer nitrogen with symbiotically fixed nitrogen could mitigate nitrous oxide (N2O) emissions in grasslands by around 130 Gg yr−1Experimentally testing this mitigation option is challenging so modeling offers means to identify the optimum legume/fertilizer combinationThe models showed that net benefits to N2O mitigation and yield can be achieved across a wide range of legume/fertilizer combinations [ABSTRACT FROM AUTHOR]

This study evaluates the dynamics of soil organic carbon (SOC) under perennial crops across the globe. It quantifies the effect of change from annual to perennial crops and the subsequent temporal changes in SOC stocks during the perennial crop cycle. It also presents an empirical model to estimate changes in the SOC content under crops as a function of time, land use, and site characteristics. We used a harmonized global dataset containing paired‐comparison empirical values of SOC and different types of perennial crops (perennial grasses, palms, and woody plants) with different end uses: bioenergy, food, other bio‐products, and short rotation coppice. Salient outcomes include: a 20‐year period encompassing a change from annual to perennial crops led to an average 20% increase in SOC at 0–30 cm (6.0 ± 4.6 Mg/ha gain) and a total 10% increase over the 0–100 cm soil profile (5.7 ± 10.9 Mg/ha). A change from natural pasture to perennial crop decreased SOC stocks by 1% over 0–30 cm (−2.5 ± 4.2 Mg/ha) and 10% over 0–100 cm (−13.6 ± 8.9 Mg/ha). The effect of a land use change from forest to perennial crops did not show significant impacts, probably due to the limited number of plots; but the data indicated that while a 2% increase in SOC was observed at 0–30 cm (16.81 ± 55.1 Mg/ha), a decrease in 24% was observed at 30–100 cm (−40.1 ± 16.8 Mg/ha). Perennial crops generally accumulate SOC through time, especially woody crops; and temperature was the main driver explaining differences in SOC dynamics, followed by crop age, soil bulk density, clay content, and depth. We present empirical evidence showing that the FAO perennialization strategy is reasonable, underscoring the role of perennial crops as a useful component of climate change mitigation strategies. [ABSTRACT FROM AUTHOR]

While crop residues could provide an additional source of revenue for agricultural producers, there are concerns that harvesting these residues could have negative effects on productivity and economic returns. Although crop residue harvest effects have been studied in wetter areas, including the U.S. Corn Belt and Southeast, there have been few studies in more arid areas. The objective of this analysis was to quantify intermediate‐term (6‐yr) effects of crop residue harvest on crop productivity and economic returns for different biomass harvest intensities and methods, and for different practices aimed at mitigating negative effects of residue harvest in the U.S. Northern Great Plains. Crop rotation treatments included spring wheat (Triticum aestivum L.)–dry pea (Pisum sativum L.), W–P; spring wheat–dry pea/cover crop mix, W–P/CC; and spring wheat–dry pea–corn (Zea mays L.), W–P–C. Biomass removal treatments included no biomass removal, bale and remove wheat straw, bale and remove residues from each crop, and graze all crop residues. Significant corn yield reductions occurred when baling crop residues, but not with grazing. However, significant spring wheat yield reductions occurred with grazing in the W–P rotation. Grazing may be more suited to the W–P–C rotation than the W–P or W–P/CC rotations as the breakeven grazing price was lower in this rotation, and the grazing treatment in this rotation had both relatively high economic returns and low economic risk over the study period. [ABSTRACT FROM AUTHOR]

Increasing crop diversity has been proposed to increase the sustainability of cropping systems. If producers are to adopt these systems, they should also be economically viable. In this study conducted near Mandan, North Dakota, four no-till cropping systems with varying levels of crop diversity were evaluated over a 12-yr period to quantify system effect on crop productivity, input use, production costs, and economic risks and returns. Cropping system treatments included a small grain–fallow rotation (SG–Fallow) and a continuous spring wheat (Triticum aestivum L.) rotation (Cont SW) as baseline low-diversity rotations, a small grain–winter wheat (T. aestivum L.)–sunflower (Helianthus annuus L.) rotation (SG–WW–Sun), a 5-yr rotation (Five Year) and a dynamic rotation (Dynamic). The SG–Fallow rotation was significantly less productive and less profitable on average than the other rotations, as measured by gross returns and net returns, respectively. However, SG–Fallow also used significantly less inputs than the other rotations. Production costs for the Cont SW and SG–WW–Sun rotations showed a significant increasing trend over time, while production costs for the Five Year rotation showed a significantly lower and slight decreasing trend over the period, with cost trends for the SG–Fallow and Dynamic rotations intermediate to these. Net returns tended to increase and relative economic risk tended to decrease as crop diversity increased from SG–Fallow and Cont SW to SG–WW–Sun, Five Year and the Dynamic system. Results from this study suggest that more diverse rotations can maintain or increase crop productivity and enhance economic viability. [ABSTRACT FROM AUTHOR]

Integrated crop-livestock systems (ICLSs) can help increase food production while benefiting soils and the environment. This review summarizes recent impacts of ICLSs on crop and livestock production and rural economics and discusses lessons learned in the northern Great Plains (NGP). Research on ICLS conducted in the NGP indicates that the crop residue grazing, swath grazing, and annual forage grazing can positively influence crop production; whereas, livestock performance varies with season, forage nutritive value, and grazing management. Furthermore, ICLSs can reduce the costs and risks of agricultural production. The success of ICLSs in NGP region depends on trade-offs, planning, economic benefits, policies, regulations, community acceptance, and management skills. The ICLSs could play a strategic role in future agricultural production. The lessons learned from adopting ICLSs in the NGP include the lack of available land for fertilizer (manure) management, that to implement ICLS practices skills and knowledge must be maintained, and ICLS provides an entry point for young farmers and ranchers however capital is needed. These experiences and lessons could be valuable references for producers to adopt ICLSs in the NGP or other regions. [ABSTRACT FROM AUTHOR]

In semiarid dryland farming regions, No-till and intensified crop rotations may improve water use. Our objective was to determine water use efficiency (WUE) and precipitation use efficiency (PUE) for spring wheat (Triticum aestivum L.; SW) grown in crop sequences representing different levels of intensification, under minimum (Min-till) or No-till. Root zone (0-122 cm) water at planting (SWP) was 2.76 cm higher for two- and three-phase sequences under Min-till than continuous spring wheat (CSW), and sequences with fallow averaged 2.65 cm higher than those without. Conversely, SWP was unaffected by sequence under No-till, with less effect of fallow. Root zone water at harvest was unaffected by the number of crop phases or fallow under Min-till. However, values for CSW exceeded the two- or three-phase sequences by 1.57 and 2.53 cm under No-till, and sequences without fallow averaged 1.52 cm more than those with fallow. The highest WUE (8.4 kg grain ha-1 mm-1 water) was observed when SW was grown in three-phase sequences compared with 7.7 kg grain ha-1 mm-1 water, for CSW and SW-fallow. Spring wheat under Min-till had higher WUE in sequences with fallow, but no effects of fallow occurred with No-till. The lowest PUE (near 3 kg grain ha-1 mm-1 precipitation) and no effects of tillage were found in sequences with fallow. However, SW in continuously cropped sequences had PUE between 5.5 and 6.4 kg grain ha-1 mm-1 precipitation and was higher under No-till. Both WUE and PUE are affected by intensification but may also be influenced by patterns of weather.

Coal surface mining in northern Great Plains USA led to reclamation experiments with soil respreading. Respread soil depth (RSD) and runoff of water redistribution (WR) effects interacted in original North Dakota studies, complicating interpretations. We determined WR and soil depth/soil quality (SQ) effects on hillslope production patterns for sites with soil wedges (2%–5% slope, 50-m length) over sodic mine spoils. At Zap, cool-season forages crested wheatgrass (CWG: Agropyron cristatum) and Russian wildrye (Psathyrostachys juncea) generally decreased as RSD increased upslope. At Stanton, alfalfa (Medicago sativa), native grasses (Bouteloua spp.), and CWG responded to RSD, increasing 70% to midslope and decreasing further. A SQ index (SQI) based on six indicator properties was highly correlated (r > 0.7) with RSD. Yield regressions with RSD or SQI were generally significant for Stanton forages and for spring wheat (Triticum aestivum) at both sites. Yield regressions with WR index (catchment area-based) indicated dominance of WR effects at Zap. Cool-season forages at Zap evidently responded to springtime runoff, while Stanton forages and spring wheat at both sites used water later in the season and responded to soil depth/SQ effects. Results suggest models for interaction of SQ and landform WR affecting productivity should include plant community composition and water-use information. [ABSTRACT FROM AUTHOR]

Management, environment, and agroecosystem type are key factors influencing photosynthetic carbon (C) uptake and C use efficiency (CUE), calculated as the ratio of net ecosystem production to gross ecosystem production (NEP:GEP). Current literature has mainly emphasized annual C balance in studies involving multiple years with continuous monitoring of ecosystem C fluxes, yet CUE has not been thoroughly analyzed during the growing season, particularly in paired comparisons of contrasting types of pasture under semiarid conditions. From 2009 through 2013, we used eddy covariance method to determine daily, seasonal, and annual C budgets in rainfed alfalfa (Medicago sativa L.) and grass ecosystems subjected to periodic harvest (haying) near Mandan, North Dakota, USA. We found consistently higher magnitudes of C fluxes (ecosystem respiration [ER], NEP, GEP) and hay production in alfalfa than grassland. Leaf area and canopy nitrogen content per unit land area were key driving factors for daily, seasonal, and annual differences in C fluxes between agroecosystems. Net ecosystem C balance indicated C losses occurred through haying in both ecosystems, though no changes in soil C stocks were detected in either ecosystem over the course of the study. Mean NEP:GEP ratios (±standard error) during periods of steady carbon dioxide (CO2) uptake before and after haying were 0.43 ± 0.01 and 0.26 ± 0.03 for alfalfa and grassland, respectively, implying more efficient C use in the former. Moreover, alfalfa had consistently greater CUE than grassland despite variations in sunlight, temperature, and precipitation within and between growing seasons. Ratios of ER to GEP were also repeatedly lower in alfalfa than grassland in all five growing seasons. Under drought conditions, we infer alfalfa roots accessed water in the soil profile unavailable to more shallow-rooted grass species. Overall, hayed alfalfa was more efficient and tolerant than grassland in assimilating and using atmospheric CO2 under variable intra- and inter-seasonal conditions. Outcomes from this study suggest the inclusion of alfalfa in unirrigated crop rotations can sustain high CUE, C uptake, and hay production while mitigating C losses in a semiarid environment. [ABSTRACT FROM AUTHOR]

Conventional farming (CONV) is the norm in European farming, causing adverse effects on some of the five major soil functions, viz. primary productivity, carbon sequestration and regulation, nutrient cycling and provision, water regulation and purification, and habitat for functional and intrinsic biodiversity. Conservation agriculture (CA) is an alternative to enhance soil functions. However, there is no analysis of CA benefits on the five soil functions as most studies addressed individual soil functions. The objective was to compare effects of CA and CONV practices on the five soil functions in four major environmental zones (Atlantic North, Pannonian, Continental and Mediterranean North) in Europe by applying expert scoring based on synthesis of existing literature. In each environmental zone, a team of experts scored the five soil functions due to CA and CONV treatments and median scores indicated the overall effects on five soil functions. Across the environmental zones, CONV had overall negative effects on soil functions with a median score of 0.50 whereas CA had overall positive effects with median score ranging from 0.80 to 0.83. The study proposes the need for field-based investigations, policies and subsidy support to benefit from CA adoption to enhance the five soil functions. [ABSTRACT FROM AUTHOR]

Long-term use of nitrogen (N) fertilizers can lead to fertility-lowering soil chemical changes. To examine this in geologically young soils in the northern Great Plains of North America, we present near-surface (0–7.6 cm) soil chemistry data from 16 years of two crop rotations: continuous crop (CC; spring wheat [Triticum aestivumL.]—winter wheat [T. aestivum]—sunflower [Helianthus annuusL.]) and crop-fallow (C-F; spring wheat—fallow) that underwent factorial tillage (none, minimum, conventional) and N rate (low, medium, high) treatments. For CC, the N rate (but not tillage) had a significant effect on pH, with the high N rate leading to the largest pH decline (−0.76). The nitrogen rate also had a significant effect on cation exchange capacity (CEC) for CC, whereby CEC increased with the N rate. Managers utilizing high N rates should be aware of the potential for soil acidification, even in the northern Great Plains of North America. [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]

In the northern Great Plains (NGP) of North America, surface sampling depths of 0 to 15 or 0 to 20 cm are suggested for testing soil characteristics such as pH. However, acidification is often most pronounced near the soil surface. Thus, sampling deeper can potentially dilute (increase) pH measurements and therefore change management recommendations. Here, we show evidence from two long-term (16-19 yr) dryland cropping experiments that soil acidification at 0 to 7.6 cm was notably diluted at both 0 to 15.2 and 0 to 30.5 cm. There were significant differences among depths for both final pH and pH change over time, with final pH being progressively higher and pH change smaller at deeper depths. Even in the relatively young, highly buffered NGP soils, acidification can occur and sampling depth for testing pH could be an important confounding factor. We suggest sampling soils at depths <8 cm for testing pH in the NGP. [ABSTRACT FROM AUTHOR]

Emphasis is placed on developing robust, productive, economically competitive, and environmentally benign agroecosystems. In 2012, after 18 yr of a study to evaluate the effects of crop sequence and tillage, we measured soil properties at various depths to 91.4 cm and estimated soil C. The experiment, near Mandan, ND, was a split-plot design, with crop sequence as whole plots and tillage (minimum tillage or no-till) as subplots. Crop sequences included continuous spring wheat (Triticum aestivum L.) with crop residue retained or removed, spring wheat--millet [Setaria italica (L.) Beauv.], spring wheat--safflower (Carthamus tinctorius L.)--fallow, spring wheat--safflower--rye (Secale cereale L.) and spring wheat--fallow. Soil organic C, calculated by the equivalent mass method (SOCem), was consistently higher (P < 0.001) than when calculated by the fixed-depth method. Disparities between the two methods, greatest near the soil surface, were attributable to tillage. Estimates of SOCem were not affected by cropping sequence at any depth, averaging about 26, 47, 73, 114 and 156 Mg ha-1 in the 0- to 7.6-, 0- to 15.2-, 0- to 30.5-, 0- to 61.0-, and 0- to 91.4-cm partitions. Tillage had no influence at depths <30.5 cm, but no-till plots contained more SOCem than minimum tillage plots in the 0- to 61-cm (115 vs. 112 Mg ha-1 ) and 0-to 91.4-cm (158 vs. 153 2.3 Mg ha-1 ) partitions (P < 0.05). Soil organic C in the 0-to 7.6-cm depth increased by an average of 3.2 Mg ha-1 or 16% since 2001. This study suggests that C sequestration in soil is less impacted by the choice of crop sequence than by tillage. [ABSTRACT FROM AUTHOR]

Anecdotal accounts regarding reduced US cropping system diversity have raised concerns about negative impacts of increasingly homogeneous cropping systems. However, formal analyses to document such changes are lacking. Using US Agriculture Census data, which are collected every five years, we quantified crop species diversity from 1978 to 2012, for the contiguous US on a county level basis. We used Shannon diversity indices expressed as effective number of crop species (ENCS) to quantify crop diversity. We then evaluated changes in county-level crop diversity both nationally and for each of the eight Farm Resource Regions developed by the National Agriculture Statistics Service. During the 34 years we considered in our analyses, both national and regional ENCS changed. Nationally, crop diversity was lower in 2012 than in 1978. However, our analyses also revealed interesting trends between and within different Resource Regions. Overall, the Heartland Resource Region had the lowest crop diversity whereas the Fruitful Rim and Northern Crescent had the highest. In contrast to the other Resource Regions, the Mississippi Portal had significantly higher crop diversity in 2012 than in 1978. Also, within regions there were differences between counties in crop diversity. Spatial autocorrelation revealed clustering of low and high ENCS and this trend became stronger over time. These results show that, nationally counties have been clustering into areas of either low diversity or high diversity. Moreover, a significant trend of more counties shifting to lower rather than to higher crop diversity was detected. The clustering and shifting demonstrates a trend toward crop diversity loss and attendant homogenization of agricultural production systems, which could have far-reaching consequences for provision of ecosystem system services associated with agricultural systems as well as food system sustainability. [ABSTRACT FROM AUTHOR]

Rigorous economic analyses are crucial for the successful launch of lignocellulosic bioenergy facilities in 2014 and beyond. Our objectives are to (1) introduce readers to a query tool developed to use data downloaded from the Agricultural Research Service (ARS) REAPnet for constructing enterprise budgets and (2) demonstrate the use of the query tool with REAPnet data from two field research sites (Ames, IA, and Mandan, ND) for evaluating short-term economic performance of various biofuel feedstock production strategies. Our results for both sites showed that short-term (<3 years) impacts on grain profitability were lower at lower average annual crop residue removal rates. However, it will be important to monitor longer term changes to see if grain profitability declines over time and if biomass harvest degrades soil resources. Analyses for Iowa showed short-term breakeven field-edge biomass prices of $26-$42 Mg among the most efficient strategies, while results for North Dakota showed breakeven prices of $54-$73 Mg. We suggest that development of the data query tool is important because it helps illustrate several different soil and crop management strategies that could be used to provide sustainable feedstock supplies. [ABSTRACT FROM AUTHOR]

Unprecedented changes in agricultural land use throughout the northern Great Plains of North America have highlighted the need to better understand the role of crop diversity to affect ecosystem services derived from soil. This study sought to determine the effect of four no-till cropping systems differing in rotation length and crop diversity on near-surface (0 to 10 cm) soil properties. Cropping systemtreatments included small grain-fallow (SG-F) and three continuously cropped rotations (3 yr, 5 yr, andDynamic) located in south-central North Dakota, USA. Soil pH was lower in the 3 yr rotation (5.17) compared to the Dynamic (5.51) and SGF (5.55) rotations (p = 0.05). Among cropping system treatments, 5 yr and Dynamic rotations possessed significantly greater soil organic C (SOC) and total N (mean = 26.3MgC ha-1, 2.5MgNha-1) compared to the 3yr (22.7MgCha-1, 2.2MgNha-1) and SG-F (19.9Mg C ha-1, 2.0MgNha-1) rotations (P = 0.05). Comparison of SOC measured in this study to baseline values at the research site prior to the establishment of treatments revealed only the 5 yr and Dynamic rotations increased SOC over time. The results of this study suggest that a diverse portfolio of crops is necessary to minimize soil acidification and increase SOC. [ABSTRACT FROM AUTHOR]

A correction is presented to the article "Perennial forages influence mineral and protein concentrations in annual wheat cropping systems."

Organic farming has been identified as promoting soil quality even though tillage is used for weed suppression. Adopting zero tillage and other conservation tillage practices can enhance soil quality in cropping systems where synthetic agri-chemicals are relied on for crop nutrition and weed control. Attempts have been made to eliminate tillage completely when growing several field crops organically. Vegetative mulch produced by killed cover crops in organic zero tillage systems can suppress annual weeds, but large amounts are needed for adequate early season weed control. Established perennial weeds are not controlled by cover crop mulch. Integrated weed management strategies that include other cultural as well as biological and mechanical controls have potential and need to be incorporated into organic zero tillage research efforts. Market crop performance in organic zero tillage systems has been mixed because of weed, nutrient cycling, and other problems that still must be solved. Soil quality benefits have been demonstrated in comparisons between organic conservation tillage and inversion tillage systems, but studies that include zero tillage treatments are lacking. Research is needed which identifies agronomic strategies for optimum market crop performance, acceptable levels of weed suppression, and soil quality benefits following adoption of organic zero tillage. [ABSTRACT FROM AUTHOR]

Conservation agricultural systems rely on three principles to enhance ecosystem services: (1) minimizing soil disturbance, (2) maximizing soil surface cover and (3) stimulating biological activity. In this paper, we explore the concept of diversity and its role in maximizing ecosystem services from managed grasslands and integrated agricultural systems (i.e., integrated crop–livestock–forage systems) at the field and farm level. We also examine trade-offs that may be involved in realizing greater ecosystem services. Previous research on livestock production systems, particularly in pastureland, has shown improvements in herbage productivity and reduced weed invasion with increased forage diversity but little response in terms of animal production. Managing forage diversity in pastureland requires new tools to guide the selection and placement of plant mixtures across a farm according to site suitability and the goals of the producer. Integrated agricultural systems embrace the concept of dynamic cropping systems, which incorporates a long-term strategy of annual crop sequencing that optimizes crop and soil use options to attain production, economic and resource conservation goals by using sound ecological management principles. Integrating dynamic cropping systems with livestock production increases the complexity of management, but also creates synergies among system components that may improve resilience and sustainability while fulfilling multiple ecosystem functions. Diversified conservation agricultural systems can sustain crop and livestock production and provide additional ecosystem services such as soil C storage, efficient nutrient cycling and conservation of biodiversity. [ABSTRACT FROM AUTHOR]

The use of commercial nitrogen (N) fertilizers has led to enormous increases in US agricultural productivity. However, N losses from agricultural systems have resulted in numerous deleterious environmental impacts, including a continuing increase in atmospheric nitrous oxide (N20), a greenhouse gas (GHG) and an important catalyst of stratospheric ozone depletion. Although associated with about 7% of total US GHG emissions, agri-cultural systems account for 75% of total US N20 emissions. Increased productivity in the crop and livestock sectors during the past 30 to 70 years has resulted in decreased N20 emissions per unit of production, but N20 emissions from US agriculture continue to increase at a rate of approximately 0.46 teragrams of carbon dioxide equivalents per year (2002-2009). This rate is lower than that during the late 20th century. Improvements in agricultural productivity alone may be insufficient to lead to reduced emissions; implementing strategies specifically targeted at reducing N20 emissions may therefore be necessary. INSET: In a nutshell:. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N20) is often the largest single component of the greenhouse-gas budget of individual cropping systems, as well as for the US agricultural sector as a whole. Here, we highlight the factors that make mitigating N20 emissions from fertilized agroecosystems such a difficult challenge, and discuss how these factors limit the effectiveness of existing practices and therefore require new technologies and fresh ideas. Modification of the rate, source, placement, and/or timing of nitrogen fertilizer application has in some cases been an effective way to reduce N20 emissions. However, the efficacy of existing approaches to reducing N20 emissions while maintaining crop yields across locations and growing seasons is uncertain because of the interaction of multiple factors that regulate several different N20-producing processes in soil. Although these processes have been well studied, our understanding of key aspects and our ability to manage them to mitigate NzO emissions remain limited. INSETS: In a nutshell:;Panel 1. N20-producing processes in soil. [ABSTRACT FROM AUTHOR]

The potential for mitigating increasing atmospheric carbon dioxide concentrations through the use of terres-trial biological carbon (C) sequestration is substantial. Here, we estimate the amount of C being sequestered by natural processes at global, North American, and national US scales. We present and quantify, where possible, the potential for deliberate human actions - through forestry, agriculture, and use of biomass-based fuels - to augment these natural sinks. Carbon sequestration may potentially be achieved through some of these activities but at the expense of substantial changes in land-use management. Some practices (eg reduced tillage, improved silviculture, woody bioenergy crops) are already being implemented because of their economic benefits and associated ecosystem services. Given their cumulative greenhouse-gas impacts, other strategies (eg the use of biochar and cellulosic bioenergy crops) require further evaluation to determine whether widespread implemen-tation is warranted. INSET: In a nutshell:. [ABSTRACT FROM AUTHOR]

Integrated crop-livestock systems have been purported to have significant agronomic and environmental benefits compared to specialized, single-enterprise production systems.However, concerns exist regarding the effect of livestock in integrated systems to cause soil compaction, thereby decreasing infiltration of water into soil. Such concerns are compounded by projections of more frequent high-intensity rainfall events from anticipated climate change, which would act to increase surface runoff and soil erosion. A study was conducted to evaluate the effects of residue management, frequency of hoof traffic, season, and production system (e.g., integrated annual cropping versus perennial grass) on infiltration rates from 2001 through 2008 in central North Dakota, USA. Imposed treatments had no effect on infiltration rate at three, six, and nine years after study establishment, implying that agricultural producers should not be concerned with inhibited infiltration in integrated annual cropping systems, where winter grazing is used. The use of no-till management, coupled with annual freeze/thaw and wet/dry cycles, likely conferred an inherent resistance to change in near-surface soil properties affecting soil hydrological attributes. Accordingly, caution should be exercised in applying these results to other regions or management systems. [ABSTRACT FROM AUTHOR]

Cropping systems in American agriculture are highly successful since World War II, but have become highly specialized, standardized, and simplified to meet the demands of an industrialized food system. Minimal attention has been given to the efficient exploitation of crop diversity and the synergistic and/or antagonistic relationships of crops in crop sequences. Objectives of our research were to determine if previous crop sequences have long-term benefits and/or drawbacks on spring wheat seed yield, seed N concentration, and seed precipitation-use efficiency in the semiarid northern Great Plains, USA. Research was conducted 6 km southwest of Mandan, ND using a 10 × 10 crop matrix technique as a research tool to evaluate multiple crop sequence effects on spring wheat (triticum aestivum L.) production in 2004 and 2005. Spring wheat production risks can be mitigated when second year crop residue was dry pea (Pisium sativum L.) averaged over all first year crop residues. When compared to spring wheat as second year crop residue in the dry year of 2004, dry pea as the second year residue crop resulted in a 30% spring wheat seed yield increase. Sustainable cropping systems need to use precipitation efficiently for crop production, especially during below average precipitation years like 2004. Precipitation use efficiency average over all treatments, during the below average precipitation year was 23% greater than the above average precipitation year of 2005. Diversifying crops in cropping systems improves production efficiencies and resilience of agricultural systems. [ABSTRACT FROM AUTHOR]

Woody plant expansion has been documented on grasslands worldwide as a result of overgrazing and fire suppression, but changes in ecosystem structure and function accompanying this phenomenon have yet to be extensively studied in the temperate semi-arid grasslands of North America. The primary objectives of this study were to determine the influence of woody plant expansion on soil carbon (C), soil nitrogen (N), and roots to a depth of 15 cm along a 42-year (1963–2005) chronosequence encompassing grassland, woodland, and transition zones in a northern Great Plains grassland. From these data, we also estimated ecosystem-level soil C and N changes associated with woody plant expansion in the top 0–15 cm of soil. We found total soil C increased across the chronosequence from grassland (5,070 ± 250 g C m−2) to woodland (6,370 ± 390 g C m−2) ( P < 0.05) at 0–15 cm soil depth. Total soil N also increased from grassland to woodland (425 ± 16 to 556 ± 30 g N m−2) ( P < 0.05) at 0–15 cm soil depth. Coarse particulate organic matter C and N increased from grassland to woodland (940 ± 100 to 598 ± 35 g C m−2, 70 ± 10 to 35 ± 1 g N m−2) at 0–5 cm soil depth. At the ecosystem-level, we estimate C and N accumulations at 0–15 cm soil depth are occurring at a rate of 18 and 1.7 g m−2 year-1, respectively. Results of this study suggest soil resources, namely soil C and N, in the northern Great Plains are changing following woody plant expansion. [ABSTRACT FROM AUTHOR]

There are concerns that restored grasslands currently under the Conservation Reserve Program (CRP) will experience increased soil erosion when they are returned to crop production. Our objective was to compare runoff, erosion, and erodibility on CRP land converted to annum hay production (permanent hayed, PH) and crop production under conventional-till (preplant disk tillage, CT) and no-till (NT) management. Erosion study was conducted in central North Dakota on Typic Argiustoll soil 6 yr after the CRP land had been converted to hay production and crop production with a spring wheat (Triticum aestivura L.) -winter wheat-dry pea (Pisum sativum L.) rotation. Runoff volumes and soil loss (by alum precipitation of sediment) were measured on 1.5 by 5 m bordered plots on 4% slope under a rainfall simulator delivering 1- to 3-h rains at 50 or 75 mm h-1, followed by three rains of 20 min or less at rates from 25 to 125 mm h-1. Erodibility was calculated from ratios and regressions of soil loss rates versus runoff rates measured at relative steady state. Runoff rates from 50 and 75 mm h-1 rains for CT, NT, and PH averaged 9, 12, and 21 mm h-1, respectively, and supported soil loss rates of 20, 7, and 8 g m-2 h-1. Erodibility of undisturbed CT, NT, and PH was 1.65, 0.29, and 0.28 g m-2 mm-1, respectively, showing NT did not differ from PH and that CT management increased erodibility six-fold above PH. Thorough disk tillage increased erodibility three-fold over CT, 15-fold over NT, and nine-fold over PH. Complete, nondisturbing residue removal increased erodibility less than tillage, from 1.2 times for CT to 2.5 times for NT. Chemically weeded NT exhibited the same Iow erodibility as the grassland PH treatment under the conditions of study-4% land slope, above average precipitation, and a residueproductive crop rotation. However, erodibility of tilled NT was significantiy higher than that of tilled PH, showing the higher inherent stability of grassland surface soil with its perennial plant root structures. [ABSTRACT FROM AUTHOR]

Assessing effects of cropping systems on soil organic mater (SOM) and soil carbon (C) changes are necessary to make accurate projections regarding sequestration and emission of CO[sub 2] by agricultural soils. This process requires substantial annual management inputs and large outlays for soil sampling and analyses. Our objectives were (1) to evaluate and test an alternative method for soil organic matter determination, (2) to determine if crop rotation and N fertilizer management significantly affected soil organic matter at the beginning (1986) or after 12 yrs (1998), and (3) to determine if total soil organic matter levels have changed after 12 years in a long-term cropping system study. Soil samples were taken in 1986 and 1998 to a depth of 150 cm in 30cm increments. Total soil organic C and organic matter by weight loss-on-ignition concentrations were determined for the soil samples taken in 1998. Results from both methods of analyses for the 1998 samples were highly correlated. No significant differences in soil organic matter by weight loss-onignition or total soil organic C concentrations between crop rotations or nitrogen (N) fertilizer rates were obtained for either sampling date, in the change in soil organic matter concentrations between dates, or total soil C amounts in the profile (0 to 150 cm) after 12 yrs (1998). Although no differences in soil organic matter (soil C) were obtained in the study, the excellent correlation between results of the two methods of organic matter analyses demonstrates that the less expensive and easier to use weight losson-ignition method can be used to make these types of assessments. [ABSTRACT FROM AUTHOR]