| Studies on nutrition diagnosis, fertilization and environmental effects in non-polluted vegetable production were conducted in the field and pot experiments In Beijing suburb. The results were summarized as follows:1. It was found that only a few kinds of mineral fertilizers were input in unreasonable proportion of nutrient supply. The mineral fertilizers of N and P were mainly urea and diammonium orthophosphate, whereas a few potassium. The varieties of organic manures tended to be readily available, 57% in open field and 77% in protected field were chicken manure. The ratio of nitrogen supply as the form of organic to inorganic were tended to be 1:1 .The nutrient supply of NPK was Unbalanced and the input/output of N and P for the Vegetables were 4 and 7 times individualy.2. Nutrition level of open vegetable field was moderate or low.The capacity of nutrient supply in protected field was significantly higher than that in open field, i.e. 48% higher in organic matter, 2.3 times higher in available phosphorus, 60% higher in available potassium and 120% higher in nitrate content. Total soil salt content and soil electric conductivity were 1.88 g-kg-1 and 0.47 ms-cm-1 individualy. Soil salt content in protected field with over 15 years of cultivation was over critical value to tolerate. Among the components of soil soluble salts, ion contents were as the following order: Ca2+>Mg2+>Na+>K+and SO42>N03>CO3:>C1-.3. NPK fertilization and diagnosis techniques for non-polluted fruit, leaf and root vegetable species were presented in the first time. The equations in response to NPK fertilizers were built for vegetable species .According to crop response, available P2O5 70-100 mg.kg-1and K2O250-300 mg.kg-1 in the soil were indexes of limiting P and K fertilizer to maintaining soil fertility level. Nmin50 mg.kg"'in the soil was index for limiting nitrogen fertilization. The of soil In the current situation fertilizer use efficiencies were 10-15% (N), not more than 16% (P) and 37% (K) in Beijing suburb.4. The ability to fix potassium in protected vegetable field as follows: clay soil>loamy soil>sand soil. Mixing application of ammonium and potassium fertilizers could inhibit soil K+-fixing capacity. In sandy soil two times of N+Kmixed sidedressing for leafy vegetable could increase vegetable yield marketable by 16%. For fruit vegetable species, no matter which kind of soil texture, three times of N+K mixing application could improve yield by20%.5. Drip irrigation could increase tomato and cucumber yields by 23.6% and 20.2% respectively, save over 50% of N fertilizer under the same yields level than furrow irrigation. It was increasing crop yield 63.9%. by driping potassium . Similar results were also found in boron application,however no effects on crop yield in furrow irrigation system.6. The relationship between contents of vitamin C, soluble solids, reducing sugar and total acidity and N applied rate met the laws of Mitscherlich and diminishing returns. Optimum N supply could obtain product with high quality. Nitrate content increase in vegetable tissue was resulted from excessive N application and irrigation. Meanwhile potassium application could reduce nitrate content in vegetable .7. At high N level, for example 450kg.hm-2, irrigation amount became the major factor to affect soil nitrate leaching. Heavy irrigation could move soil nitrate down to over 90cm deep; on the other hand nitrate leaching did not occur with water-saving irrigation. Heavy rain in summer season could also move, over 50% of soil residual Nmin from surface layer down to deeper layer.8. The application of specific compound fertilizer and the technique of quantitative use of organic manure significantly increased crop yield of leaf and fruit vegetables. Active organic manure and ammonium sulfate reduced nitrate content in vegetable by 41.5%, and no effects on vitamin C. Compared to common fertilizer, microbial fertilizer had some positive effects on vegetable growth, whereas no significant differences between microbial ferti...
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