Korean Journal of Soil Science and FertilizerISSN:0367-6315(Print) 2288-2162(Online)한국토양비료학회

Urea is the most commonly used nitrogen fertilizer in agriculture due to its high N content and low transportation cost. A significant portion of urea-N applied in soil is often lost via ammonia volatilization, leaching, and denitrification. At high temperatures, urea is converted to starch carbamate by reacting with starch. Starch carbamate can be used as a slow-release fertilizer because of its low solubility and mineralization rate. A pot experiment of growing lettuce was conducted to investigate the effects of starch carbamate on crop growth and nitrogen loss in soil. Three treatments were urea, starch-urea mixture, and corn starch carbamate. In all treatments, soil pH after lettuce cultivation decreased compared to before, but was not different (P > 0.05) among treatments. The corn starch carbamate treatment had higher NH₄⁺ and NO₃^- contents than the urea treatment, reflecting the lower mineralization rate of corn starch carbamate. The amount of nitrogen loss due to leaching was lowest in the starch carbamate treatment, but the difference between treatments was not significant (P > 0.05). The dry weight of lettuce in the corn starch carbamate treatment increased by 79% compared to the urea treatment, probably due to alleviation of ammonia toxicity in the corn starch carbamate. These results indicated that nitrogen was relatively slowly mineralized in the starch carbamate treatment compared with the urea treatment and so had lower chance of leaching and causing ammonia toxicity to plants. Thus, starch carbamate can be used as a slow-release fertilizer to reduce ammonia stress in plants and nitrogen loss by leaching.

Nitrogen uptake of lettuce treated with urea, starch-urea mixture, and starch carbamate.