| 1 Compared with NU with equal nitrogen applications, controlled released urea(CRU)effects were that: dry matter cumulation rate in tomato leaves and stems were increased by 32.8% and 53.1% respectively;while at tomato harvesting stage the dry matter cumulation rate was increased by 34.9%; and the yield was increased by 20.1%;the chlorophyll and NR activity in tomato leaves at different stages were higher,and the diversity were remarkable. Controlled Nl(300kgN/hm2) compared with normal Nl(600kgN/hm2) and Controlled N2(600kgN/hm2) compared with normal N2(1200kgN/hm2) ,namely that's under the condition of nitrogen applications were reduced by half ,the dry matter cumulation rate of tomato was increased by 23.2%and 37.5%respectively ,the yields was also increased by 8.4% and 25.0%.The yield increasing impact reached remarkable level and most remarkable level. With equal nitrogen applications CRU also increased radish and Chinese cabbage yields by 25.2%-37.6% and 25.9%-66.9% respectively .2 Compared with NU with the equal nitrogen application,CRU increased candy and vitamin c content of tomato by 20.5%and 62.4% respectively. While for radish and Chinese cabbage it were 15.1%-28.9% and 19.8%-32.6%,and for radish candy was increased by 10.3%-15.2%and vitamin c 10.4%-18.0%.But tomato fruit total acidity was reduced by 24.2% .That indicated that CRU remarkably improved the nutrient quality of vegetable. Under the same condition ,CRU reduced nitrate-N content in Chinese cabbage and radish with CRU treatments were reduced by 58.0%-65.5% and 37.0%-61.8% respectively.The reducing impact of nitrate-Ncontent in vegetable blades was the most remarkable,secondly the petiole,the root was the worst.3 CRU improved vegetable nutrient absorbing and NUR.For tomato ,the use ratio of CRU was 37.95%-62.66%, 21 percentage higher than that of NU with the equal nitrogen applications. While for radish and Chinese cabbage that were 48.26%-78.35% and 39.64%-76.04% respective, 19.17 and 17.41-44.85 percentage higher.4 Except for former stage ,the nitrogen content in tomato leaves with CRU treatments were all higher than that of NU.Form period of harvesting beginning to period of full fruit ,the nitrogen content in leaves with controlled-N2 treatment was increased by 14.70%,while Niwas reduced by 24.10%.This reflected that the providing time of CRU was longer ,and nutrient providing intensity was greater ,that indicated the consistency of nutrient release of CRU with tomato nutrient absorbing ,and CRU could meet the nitrogen requirement of tomato .5 CRU was helpful to better soil properties. The plowed layer soil PH was raised by 0.03 unit after harvest stage.while NU with the equal nitrogen applications declined 0.26 unit.The 60-100 soil layer PH was declined 0.2land 0.38 unit , That showed that CRU could staved soil acidification proceed caused by nitrogen application to some extent..6 After the ending of procreation stage ,the soil nitrate content in plowed layer of CRU and normal urea treatments were 38.5mg/kgand 16.7mg/kg respective. In 40-60cm layer, the nitrate content with CRU treatments were lower at majority stages than normal urea.And 60-100cm layer was the same . Thus it can be seen that ,CRU could increase plowed layer soil available nitrogen content after the growing season, contemporary lessened nitrate leaching to lower soil layer .7 CRU has the function of controlling nutrient release ,so the leaching loss of CRU mainly took place at nutrient releasing peak period. Compared with NU with equal nitrogen applications, nitrogen loss ratio of CRU was reducedby 38.37 percentage in soil - plant system.Seen from leaching model, the loss ratio of CRU was 19.03-28.45 ,and 19.92-30.9 percentage lower than that of NU. |
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