Study On The Synergy Mechanism Of Polyaspartic-acid/salt(PASP) Urea And Modified Urea To The Crops

Heavy and inefficient use of chemical fertilizersespecially abundant of urea resulted lower nitrogen(N) use efficiency and produced negative effect to the mankind such as the serious environment pollution. Exploration and application of novel type of fertilizers have become the most direct and effective way to solve this problem. On the one hand, fertilizer synergist can boost the crop yields obviously. Polyaspartic acid(PASP) is one of the most efficient fertilizer synergist, which has several advantages, such as being phosphate-free, non-toxic and biodegradable. Recent years, PASP has been applied in the fertilizers increasingly. On the other hand, modified urea can slow the release of N in soil, which can provide nutrients to crops for a long time and improve the N use efficiency of the Urea. The synergy mechanism and application effect of PASP urea and modified urea were researched in this paper:(1) The influence of PASP on nitrogen leaching, nitrification inhibition, ammonia volatilization, the N2 O emission and the crop cultivation were investigated in detail via, leaching experiment, culture experiment, static absorption experiment and cultivation experiment(corn, lettuce and wheat). The results revealed that the treatments using PASPs inhibit the transformation of ammonium-N into nitrate-N as well as the leaching loss of ammonium-N and nitrate-N, reduce the amount of ammonia volatilization and N2 O emission flux,can increase the yield and N/P/K uptake. The order of theeffect of these three treatments with PASP is modified PASP-Ca>PASP-Ca>PASP-Na.(2)The release characteristic of modified urea in water was investigated bydissolution experiment. The resultrevealed thatthe modified urea can slowrelease in water compared with urea, and the release time can be controlled by the addition of urea to modified urea. The results of corn and wheat cultivation experiments indicated thatmodified urea can provide nutrients to crops for a long time, increase the corn yieldand fertilizer use efficiency.It was also found that the yield of crop increased with the reduction of modified urea 20 %.Modified urea can be one-pot applied to the soil to meet the requirements of crops,and the dosage of fertilizer can also be decrease.The synergy mechanism of PASP-urea and modified urea is different.The yield of the crop and the N use efficiency can be improved via reducing the N loss and improving the N absorption of crops, for PASP-urea and slow release for modified urea. PASP-ureahas the advantages of the low cost and biodegradable, however, the topdressing is needed in a long growing season crops such as corn and wheat. While the modified urea can be one-pot applied to the soil with a higher cost compare with PASP-urea.