The effects of declining soil moisture levels on suitable maize cultivation areas in Northeast China

Soil moisture (SM) is the most direct and important source of crop water requirement. The change in SM levels and the maize water requirement (MWR) will, under the influence of climate change, lead to changes in the areas that are suitable for maize cultivation in Northeast China (NEC). To quantitatively investigate these changes, the study analyzed the spatiotemporal changes in the SM and MWR in NEC from 1961 to 2010 using Global Land Data Assimilation System (GLDAS) SM products, meteorological data and land use data. The following conclusions were reached: 1) In the past 50 years, there has been an obvious trend of soil drying in NEC, and the equivalent water thickness at the depth of 0-200 cm has decreased by 71.06 mm (12.78%), which is more serious in agricultural areas (77.09 mm, 13.86%). 2) From 1961 to 2010, the air temperature in NEC increased by about 1.8 degrees C in 50 years.. 3) The shortage in maize water calculated by SM and MWR showed that areas unsuitable for maize cultivation increased by approximately 66,250 km(2), an area close to one-third of the dry farmland area in NEC; and 4) the slightly decreased precipitation and increased air temperature were the major driving factors for the decrease in the suitable maize cultivation area. If the maize was planted in unsuitable areas for a long time, it may lead to excessive use of groundwater and surface water. Therefore, these results provide a base for decisionmaking regarding adjustments to the cultivation structure in NEC.