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Crop Sequence and Nitrogen Fertilization Effects on Soil Properties in the Western Corn Belt

Liebig, M. A., Varvel, G. E., Doran, J. W., Wienhold, B. J.
Soil Science Society of America journal 2002 v.66 no.2 pp. 596
Zea mays, continuous cropping, crop rotation, Glycine max, Avena sativa, Trifolium pratense, soil organic matter, soil fertility, nitrogen, soil chemistry, soil microorganisms, application rate, soil organic carbon, Nebraska
Understanding long-term management effects on soil properties is necessary to determine the relative sustainability of cropping systems. Soil physical, chemical, and biological properties were measured in a long-term cropping system study in the Western Corn Belt. Properties were evaluated after 16 yr in four crop sequences [continuous corn (L.) (CC), corn–soybean [Glycine max. (L.)] (C–SB), corn–oat (L.) + clover (80% sweet clover [ L.] and 20% red clover [ L.])–grain sorghum [((L.) Moench)–soybean (C–OCL–SG–SB), and corn–soybean-grain sorghum–oat + clover (C–SB–SG–OCL)] each at three N fertilization rates (ZERO, LOW, and HIGH) to a soil depth of 30.5 cm on a Sharpsburg silty clay loam (fine, smectitic, mesic Typic Argiudolls). Nitrogen fertilization had a greater impact on soil properties than crop sequence, with management effects most pronounced at 0 to 7.6 cm. Increased N rate resulted in greater organic C, total N, and particulate organic matter (POM), but lower soil pH. Increased N rate also reduced microbial biomass by ∼20% between the HIGH and ZERO N-rate treatments. The C–SB–SG–OCL sequence possessed more potentially mineralizable N (PMN) (57 vs. 46 kg ha for average of CC and C–SB) and a higher percentage of POM present as soil organic matter (17.1% for the C–SB–SG–OCL sequence vs. 13.9% for other sequences). Within the context of soil functions and cropping system performance, results from this study indicate the C–SB–SB–OCL sequence enhanced nutrient cycling efficiency, while N fertilization resulted in a trade-off between its positive effect on biological productivity and negative effect on nutrient cycling efficiency.