Absorption Characteristic of Nitrogen for Rice Roots Under Water-saving Irrigation

To clarify the absorption characteristics of nitrogen for rice root under water-saving irrigation from paddy field, pots experiment with different nitrogen levels under water-saving irrigation rice was conducted. Nitrogen distribution in root zone was obtained. Root nitrate nitrogen uptake rate was determined by using optimal perturbation iteration algorithm to inverse nitrogen migration equation. In addition, the relationship between root nitrate nitrogen uptake rate and indicators of root growth was analyzed. The results showed that soil nitrate nitrogen leaching losses from paddy field under water-saving irrigation was comparatively large. Soil nitrate nitrogen concentration decreased with the increase of days after fertilization. Soil nitrate nitrogen concentration increased with the increase of soil depth. Nitrate nitrogen uptake rate of rice root with high N treatment increased by approximately 1.311% and 0.993% after tillering fertilizer (DAT= 21 similar to 50) and panicle fertilizer (DAT= 59 similar to 107) respectively compared to low N treatment. Nitrogen deficiency enhanced the nitrate absorption capacity of unit specific root length, reduced the nitrate nitrogen absorption capacity of nitrogen per unit mass of roots. Nitrogen deficiency in early growth stage enhanced the nitrate nitrogen absorption capacity of rice unit root length, but the sustained deficiency can not maintained the nitrate nitrogen absorption capacity of rice unit root length. Proper nitrogen deficiency has less effect on the absorption of nitrate nitrogen for rice root and it benefits to improve the nitrogen utilization efficiency in paddy field.