Residual Effects of Nitrogen Application for Six Consecutive Crop Seasons on Soil Nitrogen Mineralization and the Succeeding Crop Yield in a Rice Paddy

The aim of this study was to determine the effects of past N fertilizations on soil N mineralization and crop yield formation in the succeeding season in a rice paddy. A field experiment was conducted to compare soil N mineralization and yield attributes of the succeeding crop in a rice paddy following four N application rates (0, 50, 100, and 200 kg N ha−1) during the previous six consecutive crop seasons. Results showed that soil N mineralization potential and maximum and mean N mineralization rates increased with the increase of rates of N applied in the previous seasons, with increases by 14–30% at the N rate of 200 kg N ha−1. Total N uptake by the succeeding crop was significantly and positively related to soil N mineralization potential and maximum and mean N mineralization rates, showing determination coefficients of 0.701–0.729. There was a significant negative relationship between internal N-use efficiency and total N uptake in the succeeding crop; namely, internal N-use efficiency for biomass production decreased by 4 g g−1 for each 1 g m−2 increase in total N uptake. The previous six seasons of N fertilizer applications did not significantly affect grain yield, yield components, total biomass production, and harvest index of the succeeding crop. These results indicate that past N applications can accelerate soil N mineralization and consequently lead to a partial increase in total N uptake by the succeeding crop, but the subsequent crop’s grain yield is not necessarily affected because the increased total N uptake can be offset by the decrease in internal N-use efficiency for biomass production. The finding of this study highlights the need to fully consider soil nutrient supply and crop nutrient-use efficiency when developing new nutrient management practices for rice production.