GROWTH, YIELD AND YIELD COMPONENTS OF LOWLAND RICE AS INFLUENCED BY AMMONIUM SULFATE AND UREA FERTILIZATION

Nitrogen (N) is one of the most important nutrients in increasing lowland rice yield. Two greenhouse experiments were conducted to evaluate influence of ammonium sulfate and urea fertilization on growth, yield and yield components of lowland rice. The nitrogen rates used were 0, 50, 100, 150, 300 and 400 mg N kg(-1) of soil. Shoot dry weight and grain yield were significantly (P < 0.01) increased in a quadratic fashion when N rate increased from 0 to 400 mg kg(-1) by ammonium sulfate as well as urea fertilization. Maximum grain yield was obtained at 168 mg N kg(-1) soil by ammonium sulfate and at 152 mg N kg(-1) soil by urea. Maximum grain yield at average N rate (160 mg kg(-1)) was 22% higher with the application of ammonium sulfate compared to urea, indicating superiority of ammonium sulfate compared to urea. Rice yield components, N uptake and use efficiency were significantly influenced with the increasing N rate from 0 to 400 mg kg(-1) of soil by both the sources of N. Plant height, shoot dry weight, grain harvest index, 1000 grain weight and N uptake and use efficiency in shoot and grain had significant positive association with grain yield. However, spikelet sterility was negatively associated with grain yield. Soil pH, soil calcium, phosphorus, and potassium contents were significantly influenced by N treatments with urea fertilization. These soil properties were not influenced significantly by ammonium sulfate treatment, except P content.