Multidecadal changes in moisture condition during climatic growing period of crops in Northeast China

Investigating the spatiotemporal dynamics of agricultural water status during crop growth season can provide scientific evidences for more efficient use of water resources and sustainable development of agricultural production under climate change. In this study, the following were used to evaluate the multidecadal changes in moisture condition during climatic growth period of crops in Northeast China from 1961 to 2010: (1) the daily climate variables gathered from 101 meteorological stations in Northeast China for 1961–2010; (2) FAO (Food and Agriculture Organization) Penman–Monteith equation; (3) 80% guaranteed probability for agro-climatic indicators; and (4) the daily average temperature stably passing 0 °C, which is the threshold temperature of climatic growth period for crops. Reference crop evapotranspiration (ET₀) and relative moisture index were further calculated. The results showed that Northeast China’s climate in the main agricultural areas over the past 50 years was warmer and drier in general, with a growing range and intensity of drought. From 1961 to 2010, when the daily average temperature stably passed 0 °C, the average annual total precipitation (P) and ET₀ with 80% guaranteed probability in Northeast China both emerged as decreasing trends with averages of 555.0 mm and 993.7 mm, respectively. However, the decline in P was greater than that of annual total ET₀. As a result, the annual relative moisture indices sharply decreased with an average of −0.44, mostly fluctuating from −0.59 to −0.25. As far as spatial distributions were concerned, the inter-regional reductions in P and relative moisture index over the past 50 years were conspicuous, especially in some agricultural areas of central Heilongjiang Province, northeastern Jilin Province and northeastern Liaoning Province. On the contrary, ET₀ obviously increased in some agricultural areas of central and northwestern Heilongjiang Province (eg. Qiqiha’er, Shuangyashan, Hegang, Suihua, etc.), and northeastern Jilin Province (eg. Baicheng). This indicated that drought existed and was unfavorable for crop growth and development, especially during the period of 2001–2010. This finding revealed that drought was still one of the most important agricultural meteorological disasters in Northeast China. Some countermeasures should be formulated to adapt to climate change. Our findings have important implications for improving climate change impact studies, for breeding scientists to breed higher yielding cultivars, and for agricultural production to cope with ongoing climate change.