Research On Water Suitability Of Maize Planting Range In Northeast China

Soil Moisture is a link between surface water and groundwater,and a key variable in hydrology and meteorology.It plays an important role in regulating rainfall infiltration and surface evaporation.At the same time,soil water is also the main source of water consumption of crops,forest grass and other plants.Too high or too low soil moisture may affect the normal growth of crops,even causes floods or drought and other disasters,affecting agricultural production and endangering the society and economy.In Northeast China,the crops are watered by rain,which are greatly influenced by natural precipitation and evaporation.Therefore,it is of great significance to study the temporal and spatial changes of soil moisture.Soil water content is closely related to the growth of crops.The water requirement for normal growth and development at different stages of crop growth varies from plant to plant.The study of water requirement during crop growing season is of great value for agricultural cultivation and water resources utilization in various regions.In this study,the monthly mean data(soil moisture,sunshine percentage,mean air temperature,mean wind speed,mean relative humidity,precipitation,and mean water vapor pressure)from 1961 to 2010 were provided by China Meteorological Data Network and the soil moisture products of four layers(0-10 cm,10-40 cm,40-100 cm and 100-200cm)for 1948-2010 years were provided by GLDAS.Based on these data,the error characteristics of GLDAS soil moisture products are evaluated.Crop water requirement is calculated based on the crop coefficient method by Penman-Monteith formula.On this basis,the temporal and spatial variation characteristics of soil moisture and the spatial and temporal distribution characteristics of crop water demand in the crop root region of Northeast China are analyzed.The water suitability of maize planting area was evaluated in order to provide services for agricultural water management and agricultural decision-making.The main results of the study are as follows:(1)Through the correlation analysis and error analysis of the GLDAS soil moisture assimilation product and the site real observation data,the results show that the correlation between the soil moisture products of the GLDAS and the measured data is good,the average correlation coefficient of 0-10 cm and 10-40 cm is 0.39,and the root mean square error and the deviation value are less than 0.07cm3/cm3 The soil moisture product can be used to analyze the temporal and spatial variation of soil moisture.(2)Based on the soil moisture data of GLDAS,the interannual variation of soil moisture in the four layers of crop roots was analyzed for 1948-2010 years,and each layer showed a decreasing trend.The soil moisture content of the four layers in the root zone of the crop growing season was weighted averaging to get the soil moisture of the depth of 0-100 cm and 0-200cm?In order to analyze with the meteorological data,the products of the GLDAS was selected from 1961 to 2010.The soil moisture in the 0-100 cm and 0-200 cm growth seasons of the whole northeast region was basically reduced,the soil moisture of 0-100 cm was reduced by about 20 mm,and the soil moisture of 0-200 cm was reduced by about 25 mm.The degree of reduction in the western region of the north area is greater than that in the East.(3)The reference crop evapotranspiration was calculated by the long time series data(1961-2010 years)and Penman-Monteith formula of 78 effective stations in the northeast region of China Meteorological data network,and the corn water requirement of each site was obtained by single crop coefficient method.Kriging interpolation was used to obtain the whole growing season and the various reproductive stages of the maize.The spatial distribution of water demand shows that the spatial distribution of water demand decreases in the direction of south-west to northeast,and the change rate of corn water demand in 1961-2010 years and 78 sites is obtained by linear fitting.The spatial distribution of the change rate of corn water demand is obtained by Kriging interpolation method,and the change rate of corn water demand is found to be 1961-2010 years.The slope is distributed at the same time as positive or negative values,but on the whole,there is no significantly increases or decreases.(4)Based on the temporal and spatial distribution characteristics of soil moisture in the crop root region of Northeast China and the time and space change of crop water demand,the water suitability of crop planting range in Northeast China was used by the difference between soil moisture and crop water demand.The corn water shortage was determined as the suitability limit of 0 values,and 2001-2010 years of corn were found.The area of water unsuitability of planting range was about 1.5 degrees east of 1961-1970 years comparing with the 2001-2010 years 0 millimeter line,and the area increased by about 70 thousand km2.If the current planting mode and water use method continued to be adopted in the future,the area of water unsuitability in the future corn planting area will continue to expand and threaten food security.