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Evaluation of microbial populations and activities, and their relationship to N cycling in soils under organic and conventional farm management was conducted in eastern Nebraska in 1981 and 1982, on an experiment initiated in 1975. The experimental treatments consisted of 3 × 4 factorial with three management systems (organic, fertilizer only, and fertilizer plus herbicide) for a 4‐yr grain/legume crop rotation plus one treatment of continuous corn (Zea mays L.) receiving fertilizer, herbicide, and insecticide (including one subplot without insecticide). Soil physical, chemical, and microbiological characterizations were made at soil depth intervals of 0 to 7.5, 7.5 to 15, and 15 to 30 cm. Soil chemical properties were significantly influenced by chemical management, primarily the application of beef (Bos taurus) feedlot manure in the organic management system. Total organic C, Kjeldahl N, and potentially mineralizable N in manure‐amended surface soils (0–7.5 cm) were 22 to 40% greater than nonmanured soils receiving fertilizer and/or herbicide. Soluble P levels were eightfold greater in manure‐amended surface soils, and soil nitrate levels after harvest in 1981 were two‐ to threefold greater to a depth of 30 cm than nonmanured chemical treatments. Soil microbial biomass, bacterial and fungal counts, dehydrogenase activity, and CO2 evolution were greater in soils planted to oat/clover (Avena sativa L./Trifolium pratense L. + Melilotus officinalis Lam.) and treatments receiving manure. Increases in microbial populations and their activities paralleled increases in soil organic C content, Kjeldahl N, and water‐filled pore space. Differences in N2 fixation and denitrification between crops and management systems were minimal—possibly resulting from suboptimal water availability at midseason sampling. No significant differences were found in measured soil physical, chemical, or biological properties due to herbicide or insecticide at field application rates.

20 to 24% higher corn yields and 10 to 15% lower soybean yields in adjacent border rows. Strip intercropping of corn (Zea mays L.) and soybean [Glycine Water stress, light quality, and shading are among the max (L.) Merr.] and grain sorghum [Sorghum bicolor (L.) Moench] and soybean may be a viable alternative to monoculture cropping to factors that affect crop yields and yield components at help reduce soil erosion. Careful study of yields and yield components different growth stages. Sixty-three percent shading of can add to understanding crop performance and contribute to design soybean plants caused abscission of half the pods (Mann of more productive systems. Rainfed and irrigated experiments were and Jaworski, 1970). Schou et al. (1978) showed that conducted in eastern Nebraska from 1988 to 1990, on a Sharpsburgshading soybean plants during reproductive growth insilty clay loam (fine, smectitic, mesic Typic Argiudoll), to quantify fluenced seed yield, but seed weight was not changed. strip-intercropping effects on crop yields and yield components. CornEgli and Yu (1991) found that shading from growth border-row and grain sorghum border-row yields next to soybean stages R1 to R5 in soybean reduced seed yields and increased significantly compared with inside rows in the strips. Inseed number, but did not affect seed size. These results creased seed number and seed weight contributed to higher corn are relevant to border soybean rows in strip interborder-row yields, while only seed number increased in grain sorghum border rows. Soybean border-row yields were lower next to all corn cropping. strips and next to grain sorghum strips at the rainfed site. SoybeanEffects of water stress on yield and yield components seed number was lower in border rows next to corn. Corn border-row in corn have been studied extensively. Eck (1986) found increases in seed number and seed weight indicate that competition for that water deficits during vegetative growth reduced resources was important in both reproductive and grain-filling periods; corn kernel number, but had little effect on weight per sorghum border-row increases in seed number suggest competition kernel. Kernel numbers were not affected by water defionly in the reproductive period. Higher corn density in border rows cits during grain filling unless severe deficits were immay further exploit a competitive advantage with soybean in the posed early in the period. Harder et al. (1982) also found reproductive period, perhaps increasing system productivity. Wholekernel number to be influenced by early stress, with system productivity of strip-intercropping systems was a maximum of 4% higher than monocultures of component crops, and gross returns G.W. Lesoing, Univ. of Missouri, 108 W. North Main, Richmond, cropped systems. Carter (1984) and Pavlish (1989) found MO 64085; C.A. Francis, Dep. of Agronomy and Ctr. for Sustainable a high positive correlation between yield and seed num-Agricultural Systems, 225 Keim Hall, Univ. of Nebraska, Lincoln, NE 68583-0949. Univ. of Nebra...

Cover crop (CC) grazing can be a potential strategy to support livestock and crop production while enhancing soil ecosystem services, but research on this potential multi-functionality of CCs is limited. We assessed 3-yr cereal rye (Secale cereale L.) CC grazing impacts on soil compaction, structure, water infiltration, fertility, and crop yields on an on-farm irrigated strip-till continuous corn (Zea mays L.) silage experiment on a sandy loam with <1% slope in west-central Nebraska. Treatments were: (a) non-grazed CC, (b) grazed CC, and (c) no CC. Across the 3 yr, cattle grazed CCs at 5.9 AUM ha −1 with grazing occurring over a 4-mo period during winter and/or spring, depending on the year. We measured soil properties within 5 d after grazing ended in spring before tilling and planting corn. Cattle grazing resulted in a 92% decrease of CC biomass, compared with non-grazed CCs. Grazing did not affect soil penetration resistance (compaction parameter), bulk density, aggregate stability, pH, and concentration of organic matter and nutrients except in the 2nd yr where it reduced cumulative infiltration by 80% and increased penetration resistance from 1.23 to 1.72 MPa but such increase was below root growth thresholds (<2 MPa). Cover crop grazing had no negative effect on corn silage yields although data were variable. Overall, CC grazing for 3 yr had small and variable effects on soils and crop yields, indicating that it can be a management option to support livestock production but more long-term data from different tillage and cropping systems, and climates are needed to further understand CC grazing implications. 1 INTRODUCTION Cover crop (CC) grazing can be a potential strategy to support crop and livestock production, diversify agroecosystems, enhance soil ecosystem services, and improve over-Abbreviations: AUM, animal unit month; CC, cover crop. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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