| Fertilizer as the main source of crop nutrients in modern agricultural production plays a significant role in improving soil fertility, increasing crop yield and improving crop quality. However, excessive fertilizers not only cause a low fertilizer utilization rate, but also lead to serious environmental pollution. Therefore, how to increasing yield and the utilization ratio of fertilizer, and decreasing pollution to the environment become the focus of modern agricultural fertilizer science. Slow/controlled release fertilizer is one of the environment-friendly fertilizers which can solve these problems. China is the largest country for the cultivation area and the consumption of vegetable. Tomato (Lycopersicon esculentum L.) and cucumber (Cucumis sativus L.) enriched in a lot of nutrients, which the human body needs, are two important vegetables, and play a very important role in people’s daily life. In this study, special slow-release fertilizers containing urease inhibitor (NBPT) and nitrification inhibitor (DCD) were produced according to the nutrient requirements of tomato and cucumber. Ammonia volatilization characteristics in soil of two kinds of vegetables special slow-release fertilizes were also studied by the experiment of "ventilating method" under laboratory conditions respectively. Nitrogen release characteristics of two vegetables special slow-release fertilizers were studied by the experiment of "soil incubating method". In addition, pot experiments and field experiments were conducted to study the effects of vegetables slow-release fertilizers on yield, quality, utilization rate of fertilizer, soil enzyme activity, organic matter and NPK content of tomato and cucumber. The main results were as follows:(1)Vegetables special slow-release fertilizers can significantly reduce the ammonia volatilization rate and cumulative ammonia volatilization amount, and thus to reducing losses. Compared with common compound fertilizer, under the same nitrogen level, ammonia volatilization are basically in the same trend, increased first, reaching up to a maximum and then decreased, and stabilized gradually. Ammonia volatilization of different fertilizer treatments reached their peak at 7th day. The peak of vegetables special slow-released fertilizer treatment is far less than that of common compound fertilizer, and showed significant differences. Ammonia volatilization value average rate of common compound fertilizer reached highest in early culture.20 days later, in addition to special-slow release fertilizer, average rate of ammonia volatilization remained at a high level and finally converge for other fertilizer treatment. Average rate of ammonia volatilization of slow-release fertilizers (TSRF1 and TSRF2), (CSRF1 and CSRF2) of tomato and cucumber of in the process of culture were 1.26,1.23 mg·kg-1·d-1 and 1.22,1.20 mg·kg-1·d-1, respectively. For cumulative of volatilization of ammonia nitrogen, at the same level of N, slow-release fertilizer for tomato reduced by 14.08%,14.49%,8.56%,8.97% and 2.61%,3.02% compared with commercial slow-release fertilizer and special fertilizer, and for cucumber, at the same level of N, slow-release fertilizer reduced by 14.56%,14.98%,8.76%,9.11% and 3.09%,3.44%, compared with commercial slow-release fertilizer and special fertilize, respectively. Ammonia accumulated release of eight treatments showed the same trend.(2) Slow-release fertilizer can significantly increase the yield of tomato and cucumber. Dry weight of plant organs overall were in the order of fruit> leaf or stem> root. The total dry weight of TSRF2 and CSRF2 treatment of tomato and cucumber were the highest, which were 115.33 and 100.59 g·pof-1 respectively. The total dry weight of tomato in two special slow-release fertilizers (TSRF2 and TSRF1) treatments increased by 18.18%,7.24%,31.40% and 13.45%,2.96%,26.15% compared with treatments of TCF, MSRF and OCF, respectively. The total dry weight of cucumber in two special slow-release fertilizers (CSRF2 and CSRF1) treatments increased by 22.46%,25.49%,50.76% and 18.14%,20.06%,45.44% compared with treatments of CCF, MSRF and OCF, respectively. The fruit dry weights of all treatments for tomato were slightly higher than that of cucumber.(3) The application of vegetables slow-release fertilizers could significantly improve quality of tomato and cucumber. Two kinds of vegetables slowrelease fertilizers increased the content of VC and free amino acid of fruit compared OCF treatment, the fruit nitrate content was declined significantly compared with OCF treatment, but effect on improving fruit reducing sugar were not obvious. Two kinds of vegetables slow-release fertilizers significantly improved the activities of SOD and POD of leaves, but it was not significant on the activity of CAT.(4) The absorption of three nutrient elements was in the order of N, K>P for two kinds of slow-release fertilizers. Nitrogen accumulation of different treatments on tomato was in the order of OCF< TCF< MSRF< TSRF1<TSRF2, and N absorption of TSRF2 was increased by 19.60%,33.65% and 39.57% compared with MSRF, TCF and OCF, respectively. Meanwhile, there was no significant difference between the two kinds of special fertilizer for tomato. The absorption for major elements of cucumber was similar to tomato, and N absorption of CSRF2 increased by 13.03%, 31.76%,34.69% and 48.11% compared with CSRF1, MSRF, CCF and OCF, respectively.(5) Special slow-release fertilizers significantly improved the content of available elements of N, P and K, and organic matter in soil. For the four kinds of soil enzyme activities, special slow-release fertilizer rich in organic matter significantly enhanced activities of urease and catalase in soil.(6) The transformation of different forms of nitrogen of special slow-release fertilizer in soil was characteristic of the reduction of NH4+-N and the increase of NO3--N, and the dynamic process and its release can be quantitative described by parabola and a kinematic equation(Nt=No(1-e-kt)), elovich equation (qt=a+blnt) and diffusion equation(qt=a+bt0.5), and the first-order kinetic equation is more of ephemeral to evaluate the nitrogen release effect of slow release fertilizer. |
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