Effect of Potassium Application Rates on Nitrogen Absorption and Utilization of Different Types of Rice

Abstract

Potassium, nitrogen and their interaction play important roles in plant growth, development and yield of rice. Appropriate potassium can stimulate nitrogen accumulation and translocation in rice. In order to identify plant nitrogen absorption, distribution and utilization characteristics of rice under potassium supply, a field experiment was conducted with four potassium rates (0, 90, 180, 270 kg ha-1 K2O) using conventional japonica cultivars (Wuyunjing 7 and Wuxiangjing 14) and hybrid japonica cultivars (86 you 8, Siyou 422) from 2004 to 2005 on Experimental Farm of Nanjing Agricultural University, Jiangsu province, China. Potassium application increased rice yield (4.56?14.77%) and nitrogen accumulation during growth stages, with the maximum from elongation stage to heading stage, but nitrogen uptake ratio decreased. Potassium application enhanced nitrogen transport amount and percentage after anthesis, as well as nitrogen accumulation in different rice organs, nitrogen distribution percentage in leaves and panicles, whereas declined nitrogen distribution percentage in culm and sheath. Nitrogen absorption from fertilizer, basic nitrogen recovery efficiency before elongation stage, nitrogen recovery efficiency during the whole growing stage, and nitrogen harvest index were raised significantly, but plant nitrogen productivity was opposite. Grain yield, nitrogen accumula- tion, nitrogen translocation amount and percentage after anthesis, and nitrogen distribution in different rice organs amounted to the maximum at K2O application rate of 180 kg ha-1, as well as nitrogen absorption from fertilizer, basic nitrogen recovery efficiency before elongation stage, nitrogen recovery efficiency during the whole growing stage. However, nitrogen absorption percentage from elongation stage to heading stage, nitrogen distribution percentage in culm and sheath, plant nitrogen productivity decreased to the minimum. The yield and nitrogen recovery efficiency of conventional japonica cultivars were higher than those of hybrid japonica cultivars.