| Compared with ordinary chemical fertilizers, slow/controlled release fertilizer have someadvantages in increasing crop yields, improving quality and reducing environmental pollution.The application of slow/controlled release fertilizer is an important means to reduceenvironmental pollution and improve the utilization of nutrient, and the research ofslow/controlled release fertilizer is a focus in fertilizer field. Currently, the main productionsof slow/controlled release fertilizer are coated slow/controlled release fertilizer and ureaformaldehyde fertilizer, however, there are some disadvantages, for example, the residualresin film from coated fertilizer can not be degraded in the soil, and the nutrient release periodof urea formaldehyde is long and could not be controlled. As a novel biodegradable polymermaterial polymeric slow/controlled release fertilizer contains a variety of nutrition elements,which was can be completely degraded in the soil by microorganism so as not to pollute theenvironment. Although the polymeric slow/controlled release fertilizer has so manyadvantages, the factors affecting the nutrient release, the nutrient release characteristics, andapplication effects and environmental benefits are not clear.In order to solve the above problem, the polymeric slow/controlled release fertilizersproduced by Research Center for Engineering Technology of Polymeric Composites ofShanxi Province was used as the experiment materials. Firstly, experiments of buffer solution,soil incubation, pot experiment and volatile leaching experiment of nutrient were employed tostudy the effect of pH, buffer temperature and soil temperature on the N, P, K release ofpolymeric slow/controlled release fertilizer, and kinetics about the N, P, K release ofpolymeric slow/controlled release fertilizer, and the relationship between soil enzymes andnutrient release. Secondly, the pot experiments of Chinese cabbage and pepper wereinvestigated to study the effect of the different solubility of polymeric slow/controlled release fertilizer on crop growth, fruit quality and nutrient absorption. Finally, the effect of polymericslow release fertilizer on reducing nutrient leaching and ammonia volatilization wereevaluated by monitoring device. The main results are given as follows:(1) The temperature and pH were important factors affecting the nutrient release ofpolymeric slow/controlled release fertilizer. Acid and alkaline condition could promote thenitrogen release of the polymeric slow/controlled release fertilizer, however, the acidicconditions was more conductive to the release of the nitrogen than alkaline. pH value wasmore closer7.0, nitrogen released more slowly. The ability of pH promoting nutrient releasewere in the order of pH4.0＞pH5.6＞pH10.0＞pH7.0＞pH8.4. Besides, the phosphorusrelease of polymeric slow/controlled release fertilizer also could be accelerated in acid-basecondition, but alkaline was more conductive to the promotion of phosphorus release than acid.However, there were no significant relationship between the potassium release frompolymeric slow/controlled release fertilizer and temperature and pH. The release characters ofnitrogen and phosphorus from polymeric slow/controlled release fertilizer can be described bythe first-order kinetic equation Nt=No(1-e-kt), Elvoich equation qt=a+blnt, parabolic equationqt=a+bt0.5. The fitting degree were the highest when the release of nitrogen and phosphoruswere described by first-order kinetics equation Nt=No(1-e-kt) and parabola equation qt=a+bt0.5,respectively.(2) Soil incubation experiment showed that the change of soil relative water content andtemperature had significant effect on nutrient release of polymeric slow/controlled releasefertilizer. Besides, the release of nutrient was consistent with nitrogen and phosphorus-relatedenzyme activity. The released amounts of nitrogen and phosphorus were the largest when thesoil relative water contents were40%and60%. With the increase of soil moisture, thenutrient release rate become slow, and the activity of urease and phosphatase decreased. Therelease amount of nitrogen and urease activity increased when the temperature increase,however, the phosphorus release of polymeric slow/controlled release fertilizer had nosignificant change under40%and60%soil relative water. Under80%and100%relative soilwater, with the temperature increasing, the phosphatase activity decrease, and the phosphorus release of polymeric slow/controlled release fertilizer would reduce. The potassium release ofpolymeric slow/controlled release fertilizer was not affected by soil moisture and temperature.The release characters of nitrogen and phosphorus from polymeric slow release fertilizercould be described by the first-order kinetics equation and parabolic diffusion equation,respectively, and the first-order kinetic equation was the most significant (r=0.847**～0.984**).(3) The low soluble polymeric slow/controlled release fertilizer could significantlyimprove the yield of pepper. Compared with common fertilizer treatments, the polymericslow/controlled release fertilizer improved pepper yield by13%and10.4%, which could meetthe nutrient requirement of pepper in whole growth period. When the amount of polymericslow/controlled release fertilizer was1/3common fertilizer, the yield of pepper treated withpolymeric slow/controlled release fertilizer still increase by8%, the output input ration wasmore than common fertilizer0.9～12times. The contents of soluble sugar and Vc of Chinesecabbage treated with polymeric slow/controlled release fertilizer were10%～40%and20%～40%higher than that treated with common fertilizer. And compared with common fertilizer,the content of nitrate in Chinese cabbage treated with polymeric slow/controlled releasefertilizer could be reduced by2～3.8times.(4) The polymeric slow/controlled release fertilizer had significant effects on reducingnutrient leaching and ammonia volatilization, the leaching order between different treatmentswas: common fertilizer (CCF)＞urea formaldehyde fertilizer (UCF)＞coated slow/controlledrelease fertilizer (CRF)＞polymeric slow/controlled release fertilizer (PRF)＞controll (CK).The leaching order of phosphorus and potassium was: urea formaldehyde fertilizer (UCF)＞common fertilizer (CCF)＞polymeric slow/controlled release fertilizer (PRF)＞coatedslow/controlled release fertilizer (CRF)＞controll (CK). Besides, the treatments of polymericslow/controlled release fertilizer and coated slow/controlled release fertilizer could effectivelyreduce the soil calcium leaching and not easy to cause soil compaction. |
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