Characteristics of precipitation in black soil region and response of soil moisture dynamics in Northeast China

Water is one of mainly limiting factors influencing agricultural productivity in black soil region of Northeast China which is rain-fed agriculture. In order to improve the sustainable soil water management, Standard precipitation index (SPI) was used to analysis precipitation conditions from 1952 to 2008, and the response of soil moisture to precipitation during 1999 to 2008 were considered based on long-term experiment in National Observation Station of Hailun Agroecology System, Chinese Academy of Sciences (CAS). Mean annual precipitation of 540 mm was observed in study site, with standard deviation of 121 mm and 473 mm occurring in growing season which accounted for 87.6% of mean annual precipitation. Seven dry/wet states were distinguished based on SPI(standard precipitation index), they are extremely dry state, severely dry state, moderately dry state, normal state, moderately wet state, very wet state and extremely wet state. Extremely dry state had a increasing trend during recent decade (1999-2008). Soil moisture at the end of growing season was increased remarkably in moderately wet year (2003, SPI=1.5), whereas, was in low level (512.2 mm) in extremely dry year (2004, SPI=-2.6), variation in annual precipitation also impacted the characteristics of soil water supply. More water stored in soil profile was consumed when chemical fertilizer and organic matter were applied, compared with no fertilizer. Therefore, there is great significance for the sustainable development of agricultural production to regulate the soil water according to the precipitation conditions.