Mapping of variable rate fertilizing and model of fertilizer application in paddy field

To obtain basic information for variable rate fertilizer for rice production， spatial variability of soil chemical properties is evaluated in a slight alkaline paddy field of approximate 130hm²．Two hundred and eighty-one surface soil samples(0～20cm)are collected from each of the 75m × 75m plots after harvest to investigate the spatial variability of their chemical properties such as organic matter， hydrolysis nitrogen，available phosphorus， and available potassium．Geostatistical analysis is carried out to examine within-field spatial variability using kriged maps and the contour maps of soil nutrients are charted．Mathematic model of variable rate fertilizing is established according to the criterion of soil nutrient，function of fertilizer and yield of paddy．The experiment shows that the yield of paddy can be stably retained in 8250～9000kg／hm² by the adopted variable rate fertilizing.