Effect of Drought and Cold Damage Cross-Stress on Maize Yield in Heilongjiang Province
Based on the observation data from agrometeorological stations from 1981 to 2016 in Heilongjiang Province， the indicators of water deficiency index (KCWDI) and accumulated temperature anomaly ≥10℃（H） from the People’s Republic of China meteorological industry standards， this paper assesses the drought and cold damage to maize during emergence-milk ripening stage separately, and stipulates the drought and cold damage cross-stress occurs at the same station in the same year. Besides, the temporal and spatial distribution characteristics of it are analyzed. The relational model between KCWDI, H and maize yield is constructed by mathematical statistical method, and the effects of single drought， single cold damage or drought and cold damage cross-stress on maize yield are investigated by comparative method. The results show that the changes of KCWDI and H are consistent with the spatial distribution of water resources and climate warming trend in the study area. During the analysis period, the sum of years of drought was 242 station years, and the sum of years of cold damage was 76 station years, while the sum of years of drought and cold damage cross-stress was 91 station years during maize emergence-milk ripening stage in the study area. The occurrence of drought and cold damage cross-stress presents a decreasing trend, and its appearance was high before mid-1990. After that, the frequency got to decline. The occurrence of drought and cold damage cross-stress in the west is higher than that in the east, and there is frequent drought and cold damage cross-stress in Songnen Plain. Correlation amid H, KCWDI and maize yield is significant (P＜0.05 or P＜0.01） in maize emergence-milk ripening stage. In a certain range of temperature and water condition, H decreases and KCWDI increases, which is unfavorable for the increase of maize yield. On the contrary，increasing temperature and decreasing water deficit is advantageous to maize yield increase. In general, there exists a trend that the more severe the degree of single drought, single cold damage or drought and cold damage cross-stress is, the lower the yield would be. Comparing the effects of the single drought (single cold damage), and combined occurrence of drought and cold damage on maize yield shows that when the time, days and degree of the single drought (cold damage) is equivalent to drought (cold damage) in combined occurrence of drought and cold damage, then the drought is superimposed with cold damage (drought), which means the trend of its disadvantageous effect on maize yield is increasing.