Studies on the Relationship Between Grain-yield and Climatic Ecological Factors in Summer Corn Under Super-high-yielding Cultivation Conditions

Cultivation experiments on super-high-yield (≥12000kg/ha) of summer corn (Zea mays L. )were conducted in Laizhou, Shangdong Province, from 1986 to 1997, and in Wenxian, Henan Province, from 1996 to 1997. The results showed that requirements of accumulated temperature and hours of sunshine for super-high-yield of summer corn could be met in normal years in the areas of the Huanghuaihai Plain. Amount of precipitation influenced the yield most strongly in indirect way among all the meteorological factors, and the relationship between them displayed significant negative correlation (r = -0. 5418). The regression equation between yield and amount of precipitation at seedling stage and grain filling stage both reached significant level, and the partial regression coefficients were - 4. 8735 and - 13. 7415, respectively. Further research revealed that the key climatic-ecological factors influencing yield were as fellows: the average temperature in the third and the ninth Xun (note: a Xun indicates ten days and the accounting of Xun was from the corresponding sowing date), the hours of sunshine in the sixth and the eighth Xun, the amount of precipitation in the sixth, the seventh and the second Xun. Results obtained by analyzing yield components of summer corn showed that grain numbers per ear (GN/E) made greater contribution to super-high-yield than kernel weight (KW) and the numbers of ears did. The key factors influencing GN/E were the amount of precipitation in the sixth and the eighth Xun and the hours of sunshine in the sixth Xun, with the correlation coefficients of - 0.6074, 0.5793 and 0.5854, respectively.