1980～1984年试验得出,在黄淮海平原水浇地以及降水较多的黄淮平原旱地,一年两熟比一年一熟生产力高近1倍,经济效益与能转换效率也高。高产的一年两熟制从土壤中成倍地取走养分,但有机质源却增加更多。试验发现,在低水肥、低叶面积系数情况下,叶面积与产量相关密切,在生产上应主攻单产,不要过多提高复种指数;而在高水肥、高叶面积系数情况下,产量与叶面积相关不显著,而与光合时间相关密切,故应主攻光合时间,在生长季节允许的地方,实行一年多熟。 From 1980 to 1984, it was found that in the Huang-Huai-Hai Plain irrigated land and the Huanghuai plain dry land with more precipitation, the annual yield of double-cropping in one year is nearly double that of one-year-old in one year, and the economic efficiency and energy conversion efficiency are also high. High-yielding crops are doubled from the soil twice a year, but organic sources increase more. The results showed that in the condition of low water and fertilizer and low leaf area coefficient, the leaf area was closely related to the yield, and the yield should be the main production in production, not to increase the multiple cropping index too much. In the condition of high water, fertilizer and high leaf area, Area is not significant, but closely related with the photosynthetic time, it should be the main photosynthetic time, where the growing season allows, the implementation of more than a year cooked.