Effect of nitrogen management during the panicle stage in rice on the nitrogen utilization of rice and succeeding wheat crops.

Background and aims The main objectives of this paper were to investigate the absorption and utilization of nitrogen applied at the panicle stage in rice for promoting and protecting spikelet and the effect of residual nitrogen on the utilization of nitrogen in the succeeding wheat crop in the rotation system. Methods A field experiment was combined with a mini-plot experiment with 15 N labelled urea applied at the panicle stage in rice. The experiments included three nutrient management treatments: F, S1 and S2. 126 kg N ha −1 , 120 kg N ha −1 , 72 kg N ha −1 labeled with 30 atom% excess 15 N were applied in rice, respectively. Results (1) Compare to conventional fertilizer management (F), the optimized fertilizer management (S1&S2) reduced the amount of nitrogen applications, whereas the rice and wheat yield did not decrease, and nitrogen use efficiency was improved. (2) At rice harvest, 4.7–10.7% of the fertilizer 15 N was found in the 0–20 cm profile. The fertilizer 15 N absorbed by the wheat during the period from jointing to heading accounted for 37.0%-51.1% of the total 15 N absorbed. (3) The sum of the ratio of nitrogen absorption from the rice panicle fertilizer applied to the crops (rice and wheat) and ratio of soil residue nitrogen in the wheat field were ordered S2 > S1 > F. Conclusion The optimized fertilization management reduced the loss of the rice nitrogen in the rice–wheat rotation system through improved recycling of rice panicle nitrogen applied in the crop-soil system. [ABSTRACT FROM AUTHOR]