1959年开始，由于播种面积减少、单产下降、自然灾害等原因，粮食产量连年下滑。
In 1959, various factors such as reduction of sown areas, less yield per unit area and natural disasters contributed to the decrease in grain output.
本文通过试验证明了栽培玉米增施化学肥料既可以提高粮食单产，又可随着粮食产量的增加而增多玉米根茬的数量。
Experiment showed that fertilizer application could increase not only the yield of maize but also the quantity of Its roots.
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