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Perennial herbaceous biofeedstocks (PHB) have been proposed to confer multiple ecosystem services to agricultural lands. However, the role of PHBs to affect change in soil condition is not well documented, particularly for treatments with multiple species. The objective of this study was to quantify potential changes to soil properties resulting from PHB treatments in central and western North Dakota over a 5-yr period. Treatments with multiple perennial plant species were hypothesized to induce greater improvements in soil condition compared to monocultures. Soil properties were evaluated in seven PHB treatments (four monocultures, three mixtures) at five sites with sampling occurring immediately prior to treatment establishment in 2006 and again in 2011 across a 0 to 1.2 m depth. Perennial herbaceous biofeedstocks had minor and inconsistent effects on soil bulk density, electrical conductivity, and soil pH, and no effect on available P and soil organic C (SOC) in 2011. Contrasts between monoculture and mixtures in 2011 yielded no significant differences for any soil property at any site. However, PHB treatments did induce significant changes in soil properties between 2006 and 2011, with substantial declines in available P (> 10 kg P ha − 1 yr − 1 ) at sites with high initial P and modest increases in SOC (0.9–5.7 Mg C ha − 1 yr − 1 ) at sites with low initial SOC. Electrical conductivity decreased at two sites, though changes were minor (− 0.08 to − 0.18 dS m − 1 ). Soil pH did not change over the 5-yr study. Results from this study underscore the value of PHBs to remediate nutrient-laden and/or degraded soils, while concurrently resisting increased salinity and fertilizer-induced acidification. [ABSTRACT FROM AUTHOR]

Abstract: Switchgrass (Panicum virgatum L.) is being evaluated as a bioenergy crop for the northern Great Plains. Field measurements of CO2, CH4, and N2O flux are needed to estimate the net greenhouse gas (GHG) balance of this biofeedstock. The study objective was to determine effects of recommended Nitrogen (N) fertilization (67 kg ha−1 of N applied) and unfertilized switchgrass on growing season soil-atmosphere CO2, CH4, and N2O flux using static chamber methodology. Mean hourly CO2 flux was greatest during periods of active switchgrass growth and was similar between N fertilizer treatments (P = 0.09). Mean hourly N2O flux was consistently greater under N fertilization than without N throughout the growing season. Overall, N fertilization of switchgrass affected cumulative growing-season N2O flux (27.6 kg ha−1 ± 4.0 kg ha−1 vs. 86.3 kg ha−1 ± 14.3 kg ha−1 as CO2 equivalents (CO2eq) for 0 kg ha−1 and 67 kg ha−1 of N applied, respectively; P < 0.01), but not cumulative CO2 or CH4 flux (P = 0.08 and 0.51, respectively). Aboveground biomass production was greater with N application (6.8 Mg ha−1 ± 0.5 Mg ha−1 dry matter) than without N (3.2 Mg ha−1 ± 0.5 Mg ha−1) (P < 0.05). Net greenhouse gas intensity (GHGI; kg GHG flux kg− 1 harvest yield as CO2eq) for switchgrass production was similar between N treatments (0.71 vs. 0.44 for 0 kg ha−1 and 67 kg ha−1 of N applied, respectively; P = 0.18). [Copyright &y& Elsevier]

Abstract: Grazing management affects ecosystem function through impacts on soil condition. We investigated the effects of long-term (over 70 years) grazing on soil properties and nitrous oxide (N2O) emission within a moderately grazed native vegetation pasture (MGP), heavily grazed native vegetation pasture (HGP), and a fertilized crested wheatgrass (Agropyron desertorum (Fisch. ex. Link) Schult.) pasture (FCWP) near Mandan, ND, USA. Grazing-induced changes in species composition and N fertilizer application contributed to differences in soil properties and N2O emission between pastures. Soil organic C (SOC) was 5.7Mgha−1 greater in FCWP and HGP than MGP at 0–5cm, whereas HGP had 2.4Mgha−1 more SOC than FCWP and MGP at 5–10cm. At 30–60cm, SOC in FCWP was 4.0 and 7.5Mgha−1 greater than in HGP and MGP, respectively. Particulate organic matter (POM) C and N in the surface 5cm of FCWP were three- and five-fold greater, respectively, than in HGP and MGP. Acidification from N fertilization in FCWP decreased soil pH and cation exchange capacity compared to HGP and MGP in the surface 5cm. Annual N2O emission was over three-fold greater in FCWP compared to HGP and MGP, and was positively associated with POM-C across all pastures (P ≤0.0001; r 2 =0.85). Results from this study suggest fertilized crested wheatgrass enhances deep storage of SOC, but contributes to surface acidification and greater N2O emission relative to native non-fertilized pastures in the northern Great Plains. [Copyright &y& Elsevier]

• N 2 O flux from ICL systems is poorly understood, particularly in North America. • N 2 O flux was least under grassland and grass-dominant cover crops. • Grazing did not affect N 2 O flux in cropland or grassland. • N 2 O flux was weakly related to volumetric water content when soil was not frozen. Integrated crop-livestock (ICL) systems can improve profitability, production efficiencies, and reduce environmental degradation. Among the many environmental metrics important for assessing the sustainability of ICL systems, nitrous oxide (N 2 O) flux occupies a central role given its effect on net greenhouse gas balance of agricultural practices. Unfortunately, there is limited understanding of ICL system effects on N 2 O flux, particularly in North America. Therefore, we measured N 2 O flux from ICL and non-ICL practices near Mandan, ND USA using static chamber methodology over a 3-yr period (Oct 2016 - Oct 2019). Treatments included grazed and ungrazed cropland and grassland on a site with gently rolling topography and fertile Haplustoll soils. Grazing was done by yearling cattle in the fall of each year (0.41-0.76 ha steer-1). Maximum N 2 O flux from cropland generally occurred in March and April when soil moisture was abundant and air temperatures exceeded 0 °C (i.e., during spring snow melt). Nitrous oxide flux was over eight times greater under cropland compared to grassland (Mean = 33.7 vs. 4.1 μg N 2 O-N m-2 h-1, respectively). However, N 2 O flux was not affected by grazing in either production system. Within cropland, N 2 O flux was greater in corn (Zea mays L.) and spring wheat (Triticum aestivum L.) phases of the rotation (Mean = 40.5 μg N 2 O-N m-2 h-1) compared to the soybean (Glycine max L.) and cover crop phases (Mean = 20 μg N 2 O-N m-2 h-1). Stepwise regression found N 2 O flux to be weakly related to volumetric water content when the soil was not frozen (r2 < 0.2). Study outcomes suggest ICL systems including grasslands or grass-dominant cover crops will be most effective at mitigating N 2 O flux. [ABSTRACT FROM AUTHOR]

Abstract: Dynamic cropping systems, which involve a long-term strategy of annual crop sequencing, require detailed information on management components known to influence crop performance. Considering that proper sequencing of crops is an important component for successful dynamic cropping systems, a research project was undertaken to determine the advantages and/or disadvantages of previous crop and crop residues for numerous crop sequences. A multi-disciplinary team of scientists evaluated crop sequence effects of 10 crops (barley, canola, crambe, dry bean, dry pea, flax, safflower, soybean, spring wheat, and sunflower) on seed yield, soil coverage by residue, soil water use, surface soil properties, and plant diseases in central North Dakota. Two years were required to establish a crop by crop residue matrix (crop matrix). During the second year (site 1, 1999; site 2, 2000) 10 crops were evaluated with a crop matrix. During the third and fourth year spring wheat (site 1, 2000; site 2, 2001) and sunflower (site 1, 2001; site 2, 2002), respectively, were seeded over the crop matrix. The seed yield of four crops (crambe, flax, safflower, and soybean) of the 10 crops evaluated in the crop matrix was influenced by the preceding crop at site 1 in 1999 an above average moisture year. The seed yield of eight crops (canola, crambe, dry bean, flax, safflower, soybean, spring wheat, and barley) was influenced by the preceding crop at site 2 in 2000 a more average precipitation year. Some of the lowest seed yields were obtained when a crop was seeded on its own residue. A synthesis of seed yield data from a given year provided overall values for positive and negative effects of crops and crop residue on subsequent crops. In general, the three legume crops had positive effects in contrast to non-leguminous crops, which usually had negative effects. However, sunflower was an exception among the non-leguminous crops; at site 2 in 2000, sunflower was positive for subsequent crops compared with canola or crambe, which had negative effects. Crop sequences composed of small cereal grains had the highest soil coverage by residue while sequences of two dicotyledonous species had considerably lower coverage. Soil water use among crops varied, ranging from sunflower with the numerically highest soil water use to dry pea with the least. Significant changes in surface soil properties due to crops were generally not detected in this short-term project. Given the variation in Sclerotinia disease incidence for canola, crambe, safflower, and sunflower within the crop matrix, it was difficult to detect significant differences based on the previous crop. Differences were evident two years later when the highest incidence of Sclerotinia basal stalk rot for sunflower was detected in plots where crambe was grown two years earlier. During the third year, when spring wheat was seeded over a crop matrix, spring wheat yields increased following 23 and 19 crop sequence treatments out of a possible 100 at site 1 and site 2, respectively, compared to the continuous wheat treatment. All crop sequence treatments that yielded better than the continuous wheat treatment were comprised of mostly non-cereal crops, demonstrating the positive impact of crop diversity on cereal crop production. The severity of leaf spot diseases on spring wheat were affected by crop sequence and fungal spore production was greatest on the continuous wheat treatment. Even though decreases in leaf spot disease severity and modest yield increases were obtained with some crop sequence treatments, significant yield increases due to reduced leaf spot disease severity were not obtained under our conditions. [Copyright &y& Elsevier]