Effects of Root Uptake Function and Soil Water on NO_3~- -N and NH_4~+ -N Distribution

The effects of root uptake and soil water on transfer and distribution of NO3 -N in arable soil were studied by using - summer maize (Zea mays L. var. Shandan9) as experimental crop. Results showed that root development and water supply had an obvious effect on the transfer and distribution of NO3 -N. Under a natural growing conditions with irrigation , the difference of - NO3 -N concentrations at different distances from the stem was smaller, but obvious difference of NO3 -N concentration was - - observed under the conditions of a limited root growth space without irrigation. Whether restricting root growth space or not, the content of soil NO3 -N decreased gradually from 10 cm to 0 cm from the stem, being opposite to the root absorbing area in soils. - When root growth space was limited, changes of NO3 -N concentration at different distances from the stem were similar to that of - soil water content. Results showed that NO3 -N could be transferred as solute to plant root systems with water uptake by plants. - However, the transfer and distribution of NH4 -N were not influenced by root growth and soil water supply, being different to + NO3 -N. -