Effects Of Different Fertilization Systems On Soil Properties And Safe Production Of Vegetables In Vegetable Land In Pearl River Delta

Excessive fertilization can lead to the deterioration of soil properties,aggravate the loss of soil nutrients,decrease the yield and nutrient content of agricultural products and have effects on the environment.Among the environmental problems,non-point source pollution is outstanding and has become an important obstacle to the sustainable development of agriculture in China.Therefore,the research on reducing the amount of fertilizer applied in vegetables land according to local conditions should be carried out.It is of great practical significance to reduce the amount of fertilizer and improve the utilization rate of fertilizer to increase vegetable yield,ensure the safe production of vegetables and promote the scientific and green development of vegetable industry.In this paper,through pot experiment,the feasibility study of vegetable weight-loss and efficiency enhancement model was carried out in the vegetable soil slightly polluted by heavy metals in the Pearl River Delta region through different fertilization methods with passivation agent addition.At the same time,the content of heavy metals in vegetables under different treatments was discussed.Based on the above research,the field experiment of Pearl River Delta vegetable field with chemical fertilizer reduction and slow-release fertilizer instead of conventional chemical fertilizer was carried out.The main conclusions are as follows:（1）Pot experiment showed that compared with conventional fertilization（CK）,30%reduction fertilization（CJ）had no significant effect on soil p H,organic matter,alkali-hydrolyzed nitrogen,available potassium and available phosphorus.The content of soil organic matter under the treatment of slow-release fertilizer Wanlishennong（WH）was significantly increased（P<0.05）,up to 19.65g·kg^-1.The treatment of CJ had no significant effect on the growth of Ipomoea aquatica Forsk,while the treatment of WH significantly increased the plant height of Ipomoea aquatica Forsk.（2）Pot experiment showed that under the same fertilization conditions,the addition of passivator could improve the soil p H,reduce the effective content of Cd and As in vegetable soil and the content of heavy metals in Ipomoea aquatica Forsk.The treatment of WH3（Wanlishennong slow-release fertilizer combined with 70%dihydrate gypsum and 30%ferric oxide）had the best passivation effect on Cd in soil,with a passivation rate of 27.69%.CJ3（30%reduction of conventional fertilizer combined with 70%dihydrate gypsum and 30%ferric oxide）had a better passivation effect on As in soil,with a passivation rate of 20.6%.The contents of Cd and As in different treatments of Ipomoea aquatica Forsk were 0.163-0.186 mg·kg^-1and 0.344-0.365 mg·kg^-1,respectively.In comparison with the national food safety standards,it was clear that the heavy metal content in vegetables under different fertilization modes did not exceed the standard.（3）In the field experiment,the yield and nutrient contents of Cucumis sativus L.,Amaranthus mangostanus L.and Ipomoea aquatica Forsk were not significantly affected in the significantly affected by the CJ treatment.Under the treatment of conventional fertilizer reduction by 50%（CT）,the available nutrient content,vegetable yield and nutrient content in soil of each vegetable field were reduced to a certain extent.In the first crop,the yield of melon vegetables Cucumis sativus L.decreased significantly and the yield in one-acre was only 4042.35 kg with the drop was 12.5%,while the yield of Amaranthus mangostanus L.didn’t change significantly.During the second season of rotation system,the yield of leafy vegetables decreased significantly（P<0.05）.The application of slow-release fertilizer（WH and EH）had no significant effect on the content of available N,P and K in soil,but it can improve the content of p H and organic matter,and reduce the activity of Cd in soil.WH treatment can improve the yield of vegetables in the second quarter of the current season and rotation system.The yield of Cucumis sativus L.,Amaranthus mangostanus L.and Ipomoea aquatica Forsk increased by 10.8%,3%and 2.1%,respectively.Compared to conventional fertilization（CK）,WH can maintain and even increase the nutrient content of soil under the condition of fertilizer reduction,and effectively improve the nutrient content and yield of vegetables.（4）In the field experiment,the Cd of Cucumis sativus L.,Amaranthus mangostanus L.and Ipomoea aquatica Forsk were 0.014-0.017 mg·kg^-1,0.122-0.134 mg·kg^-1and 0.141-0.149 mg·kg^-1,respectively,which didn’t exceed the standard according to the national food safety standard.