The Effect of Fertilization on Soil Water Deficit in Arable Land in Black Soil Region

The black soil region in Northeast China is the second largest granary of China.The seasonal drought caused by the uneven distribution of annual precipitation threatens the crop yield in this region.However,information about when water deficit could happen is limited.Based on observed soil water data and climate data from the National Field Research Station of Agro-ecosystem in the Chinese Academy of Sciences from 1999 to 2008,combined potential evapotranspiration calculated from Penman-Monteith euquation,soil water deficit was obtained from the difference between soil water content in root activity zone and potential evapotranspiration.No water deficit was observed in whole growing seasons,but water deficit period was found in June and July with water deficit amount of 2.34 mm and 7.04 mm,which was over 90% and 50% probability of water deficit occurrence respectively.The main factors impacting soil water deficit were the distribution of rainfall and fertilization practices.The effect of different fertilization practices on soil water deficit showed an increasing order of no fertilizer < chemical fertilizer < chemical fertilizer plus organic manure.Therefore,the application of fertilization resulted in soil water deficit in the study site,and it is essential to pay more attention to the effect of water deficit on crop yield.