The yield and dynamics of soil nitrate for summer maize on the plain of northwest Shandong province

Abstract

The water and nitrogen applications are the two main factors that affect the nitrate leaching on farmland. The field experiment was conducted to analyze the nitrate leaching and yield under different nitrogen and water application rates in summer maize field. The result indicated that there was no distinct yield difference between the higher water treatment (with soil moisture controlled between 70%FC and 100%FC in 0～50cm) and the lower one (between 55%FC and 85%FC), while the nitrogen rate had evident effect on yield with the yield reaching the maximum at about 200 kg N ha -1,and significant effect on nitrate leaching. Higher water application could accelerate the leaching of nitrate evidently. Under higher water level, the soil nitrate concentration peaks appeared at deep layers more easily than those under lower water level as an indication of nitrogen leaching, meanwhile the nitrate concentrations of soil water at depth of 200 cm were all higher than the national drinking water limit (10 mg NO- 3-N L -1). Comparatively, under lower water treatment the nitrate leaching depths are all less than those under higher water treatment, but NO- 3-N L -1 concentrations of soil solution under level of 200 and 300 kg N ha -1at the depth of 200 cm still exceeded the national drinking water limit (10 mg NO- 3-N L -1). When NO - 3-N in 100cm soil profile came to about 450 kg N ha -1 the soil NO- 3-N concentration at soil depth of 200cm would rapidly rise to 130 mg L -1 from 40 mg L -1 ,at the same time the nitrogen rate just reached 230kg N ha -1,which mean that the nitrogen rate should be under about 230kg N ha -1.