Effect Of Pouring The Chinese Milk Vetch Into The Field And Nitrogen, Fertilizer On Rice Growth, Heavy Metal Content And Nutrient Balance In Paddy Field

In order to investigate the effects of combined application of Chinese milk vetch(Astragalus sinicus L.)and different levels of nitrogen(N)fertilizer on rice growth and nitrogen,phosphorus and potassium nutrient balance,and provide scientific basis for chemical fertilizer reduction in paddy field,the study conducted the experiment in the agricultural science and technology park at Jiangxi Agricultural University during the year of 2014 to 2016.Field treatments were set with four N application levels(90 kg?hm-2,120kg?hm-2,150 kg?hm-2and 180 kg?hm-2)under 22 500 kg?hm-2Chinese milk vetch using the winter fallow field with general N fertilizer level(150 kg?hm-2)as the control.It was comprehensively evaluated the effects of Chinese milk vetch and different levels of N fertilizer on the rice yield,nutrient uptake,soil nutrient content and nutrient balance,and determinate more suitable N level under application of Chinese milk vetch.The results showed as fellows:1.The treatments with Chinese milk vetch combined with N fertilizer having higher yield results.Compared with the control,the annual total output of all N application treatments average increased by 4.19% in 2015.Specifically,the yield of the treatment with Chinese milk vetch combined with 90 kg(N)?hm-2was the most significant effect,which was 15300 kg?hm-2,increased rice yield by 5.11% compared to the control.The annual total output of all N application treatments average increased by 6.93% in 2016.Specifically,the yield of the treatment with Chinese milk vetch combined with 120kg(N)?hm-2was the most significant effect,which was 14520 kg?hm-2,increased rice yield by 11.01% compared to the control.According to the two-year production data,although the yield of the treatment with Chinese milk vetch combined with 90 kg(N)?hm-2was higher in 2015,there was no significant difference in the yield of the treatment with Chinese milk vetch combined with 120 kg(N)?hm-2.In 2016,the yield of the treatment with Chinese milk vetch combined with 120 kg(N)?hm-2was highest and significantly higher than that of other treatments.It can be seen that Chinese milk vetch combined with 120kg(N)?hm-2 treatment of the best results.In this study,we found that the combined application of Chinese milk vetch and N fertilizer could increase the grain yield per panicle and the effective panicle number.2.The combined application of Chinese milk vetch and N fertilizer is beneficial to promote the dry matter accumulation and nitrogen,phosphorus and potassium uptake ofrice plants.All treatments with Chinese milk vetch combined with N fertilizer had higher dry matter accumulation than the control.Specifically,the treatments with Chinese milk vetch combined with 180 kg(N)?hm-2increased dry matter by 19.32% compared to the control.The combined application of Chinese milk vetch and N fertilizer contributes to the transport of dry matter,the best effect of 150 kg(N)?hm-2with Chinese milk vetch.Although the combined application of Chinese milk vetch and N fertilizer promoted the accumulation of dry matter,the difference was not significant.3.There was no significant effect on the content of heavy metals in paddy field under the treatment with Chinese milk vetch combined with N fertilizer.There was no significant difference in heavy metal content in rice and soil heavy metal content between treatments.4.The amounts of N?P?K accumulation of rice treated with Chinese milk vetch and N fertilizer were higher than the control,increased respectively by 20.52%—34.70%?17.08%—39.25% and 23.69%—35.10% compared to the control.Nitrogen,phosphorus and potassium harvest index showed that the treatments with Chinese milk vetch combined with N fertilizer were higher the control,which indicated that the combination of Chinese milk vetch and N fertilizer was beneficial to the accumulation of nitrogen,phosphorus and potassium in plant grain,the nitrogen harvest index was the highest with 90 kg(N)?hm-2,but it is not significant with Chinese milk vetch combined with 120kg(N)?hm-2,the phosphorus and potassium harvest index was the highest with 120 kg(N)?hm-2,indicating that Chinese milk vetch combined with 120kg(N)?hm-2 treatment is most conducive to plant nutrient uptake.5.The combined application of Chinese milk vetch and N fertilizer can improve the nutrient content of soil nitrogen,phosphorus and potassium.The contents of total nitrogen,total potassium,alkaline hydrolysis nitrogen and available potassium were significantly higher than the control,but the content of total phosphorus and available phosphorus is not much different,it indicated that the combined application of Chinese milk vetch and N fertilizer could significantly increase the nitrogen and potassium contents of soil,but had little effect on phosphorus content.Based on the above six indexes,the soil nutrient content of the treatment with Chinese milk vetch combined with 150 kg(N)?hm-2was the highest.6.Nitrogen and potassium fertilizer should be stabilized and reduce the application of Phosphorus fertilizer under the treatments with Chinese milk vetch combined with N fertilizer.By comparing the nutrient balance coefficients of nitrogen,phosphorus and potassium,the application amount of nitrogen fertilizer and the amount of crop uptakewere basically the same,which indicated that the use of nitrogen fertilizer was reasonable,especially the treatment with Chinese milk vetch combined with 90 kg(N)?hm-2,its coefficient is close to 1,so the nutrient utilization rate is the highest.The phosphorus surplus of each treatments is more,the nutrient balance coefficient is greater than 1,easily lead to waste of phosphorus.The nutrient balance coefficient of Chinese milk vetch combined with 120 kg(N)?hm-2was lower than that of other treatments,which indicated that this treatment was beneficial to the absorption of phosphorus.The amount of potassium application was slightly higher than that of crop uptake,although the surplus was not high.In summary,combined application of Chinese milk vetch and N fertilizer can promote rice yield,improve the ability of plants to absorb nutrients,improve soil fertility.The result indicated that combined application of Chinese milk vetch with 120 kg(N)?hm-2was satisfactory.