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美国主要农产品平均单产是不断提高的。自1940—1949年以来,玉米和高粱的单产超过1倍,小麦增产接近1倍,棉花增产75%,大豆增产50%左右,苜蓿干草增产1/3。每英亩的最高单产:苜蓿为15吨以上(合每市亩5,000斤—译者注,下同),玉米230蒲式耳(合每市亩2,709斤),棉花2,500磅(合每市亩375斤),高梁215蒲式耳(合每市亩1,819斤),大豆75蒲式耳(合每市亩680斤),小麦166蒲式耳(合每市亩1,505斤)。高产栽培措施的基本要求是:1、选用具有高产潜力的适应品种,并采用优质种子;2、采用最适宜的播种日期和种植密度;3、尽量减少因肥、水不足或过多以及杂草和病虫为害造成的损失,及时完成一切作业,使植株获得最佳生长和产量。高产的基础是有高产潜力的土壤。理想的土壤是平坦的、有高代换量的壤土,且持水量大,排水
The average yield of major agricultural products in the United States is constantly rising. Since 1940-1949, the yield of corn and sorghum has more than doubled, the yield of wheat has nearly doubled, the yield of cotton has increased by 75%, the yield of soybean has increased by 50% and the yield of alfalfa hay has increased by 1/3. The highest yields per acre: 15 tons for alfalfa (5,000 pounds per mu per acre), 230 bushels for corn (2,709 pounds for each mu), 2,500 pounds for cotton (375 pounds for each acre) 215 bushels of sorghum (1,819 kg per mu), 75 bushels of soybeans (680 kg per mu), and 166 bushels of wheat (1,505 kg per mu). The basic requirements for high-yielding cultivation measures are: 1. Use suitable varieties with high yield potential and use high-quality seeds; 2. Use the most suitable sowing dates and planting densities; 3. Minimize the risks due to fertility, inadequate or excessive water and weeds and Pest damage caused by damage, timely completion of all operations, so that plants get the best growth and yield. The basis for high yield is soil with high yield potential. The ideal soil is flat, with high displacement of loam, and holding a large amount of water, drainage