Crop rotation influences yield through its effects on nutrient and pest cycles, soil C, water availability, and soil physical and chemical properties. A cropping system study was conducted from 2004 to 2008 near Brunswick, NE, on sandy loam (Haplustolls) soils to evaluate improvements of irrigated corn (Zea mays L.) yield and N use efficiency (NUE) when following soybean [Glycine max (L.) Merr.] in 2 yr as corn following soybean (CS) or in 3 yr as first-year corn following soybean (C1) and second-year corn following soybean (C2) compared with continuous corn (CC). SPAD readings at V10 and R2 were approximately 3 to 4% greater in CS than CC, indicating more inseason N availability. Corn grain yield of CS (12.1 Mg ha−1) was 20% greater than CC (10.1 Mg ha−1), with 69 and 57% greater NUE and N recovery efficiency, respectively. At zero N applied, corn harvest index was 15% greater in CS with 37% increased plant N uptake at harvest compared with CC. In CS, fertilizer replacement value estimated soybean N credits of 66 and 49 kg N ha−1 based on grain yield and plant N uptake, respectively. The difference in N rates needed to produce maximum grain yield of CS vs. CC was estimated at 32 kg ha−1 soybean N credit. The average soybean N credit was 49, 41, and 26 kg N ha−1 for the corn in CS, C1, and C2, respectively. Both the 2- and 3-yr corn–soybean rotations on loamy sand soils improved corn yield and NUE.
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机译：轮作通过对养分和害虫循环，土壤碳，水的利用率以及土壤理化性质的影响来影响产量。 2004年至2008年，在内布拉斯加州内的不伦瑞克省附近的沙质壤土（Haplustolls）上进行了种植系统研究，以评估追肥大豆后的灌溉玉米（Zea mays L.）产量和氮利用效率（NUE）的改善情况[Glycine max（L 。）Merr。]，与连续玉米（CC）相比，在大豆（CS）之后的2年中为玉米（CS），在大豆（C1）之后的3年中作为第一年玉米（C2），在大豆（C2）之后的第二年玉米中。 V10和R2处的SPAD读数在CS中比CC大约高3％至4％，表明季节N的可用性更高。 CS（12.1 Mg ha-1）的玉米籽粒产量比CC（10.1 Mg ha-1）高20％，NUE和N回收效率分别高69％和57％。施氮量为零时，CS的玉米收获指数比CC高15％，收获时植物氮的吸收增加了37％。在CS中，基于谷物产量和植物氮素吸收量，肥料替代价值估计分别为66和49 kg N ha-1的大豆氮素信用。产生CS和CC的最大谷物产量所需的氮肥速率差异估计为32 kg ha-1大豆氮素。在CS，C1和C2中，玉米的平均大豆N信用分别为49、41和26 kg N ha-1。在壤质沙土上的2年和3年玉米-大豆轮作均可提高玉米产量和NUE。
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