| environ. |
crop rotation An agricultural technique in which, season after season, each field is sown with crop plants in a regular rotation, each crop being repeated at intervals of several years. Crop rotation minimizes the risks of depleting the soil of particular nutrients. In rotation systems, a grain crop is often grown the first year, followed by a leafy-vegetable crop in the second year, and a pasture crop in the third. The last usually contains legumes; such plants can restore nitrogen to the soil. Notwithstanding, high yields tend to depend upon the continued addition of chemical fertilizers to the soil (一种农业技术。在各季节间，每块土地都会被有规律的播种和种植农作物，每种农作物都会在间隔几年后被重复种植。轮作可以将土壤特殊养分被耗尽的危险性降到最低。在轮作系统中，榖类作物一般在第一年种植，接着的第二年是多叶蔬菜作物，第三年是放牧作物，最后是豆类作物，因为这类作物可以恢复土壤中的氮肥。 尽管如此，高产量向土壤中连续投加额外的化学肥料。) |
