Abstract: Based on the data of summer average temperature, precipitation, sunshine hours, spring maize development period and yield in Xifeng district of Qingyang city from 1990 to 2018, the variation characteristics of summer average temperature, precipitation and sunshine hours and their effects on spring maize development period and yield were analyzed. The results showed that the average temperature in summer was on the rise, and the rising rate was 0.46 ℃ per 10 years. Precipitation showed an increasing trend of fluctuation with an increase rate of 4.22 mm per 10 years; sunshine hours showed a decreasing trend, and the decreasing rate was 4.76 h per 10 years. The average development periods of spring maize in the years with higher average temperature in summer were earlier than those in the years with lower average temperature, the number of days of the whole growth period was shortened, and the average climatic yield was low. The average development period of spring maize in the years with more precipitation in summer was delayed compared with that in the years with less precipitation period was prolonged, and the average climatic yield was high. Summer sunshine hours advanced the average growth period of spring maize, but had little effect on the whole growth period and average climatic yield. Precipitation was the most significant factor affecting climate yield in summer, followed by temperature. The correlation between sunshine hours and climate yield was the least obvious. The most significant correlation between average temperature and climate yield is jointing-tasseling stage; the most significant correlation between precipitation and climate yield is jointing-tasseling stage; the most significant correlation between sunshine hours and climate yield is flowering-silking.

Key words: summer climate, variation characteristics, yield of spring maize during development and climate, impact analysis and assessment