| The area of vegetable planting in Taihu Lake is wide,the input of nitrogen fertilizer is large,and the utilization rate of nitrogen fertilizer is low.The agricultural non-point source pollution causes great damage to the ecological environment,and brings a series of additional pollution problems to air,soil and water,which is not conducive to the sustainable development of modern agriculture.Therefore,innovative research should be carried out around the varieties and amount of nitrogen fertilizer to reduce NH3 volatilization and N2O emission in vegetable fields under the premise of maintaining vegetable yield and not affecting vegetable quality,so as to improve the comprehensive benefits such as environmental benefits,economic benefits and agricultural benefits.This study conducted filed experiments to comprehensive evaluate the benefits of different nitrogen fertilizers types used in vegetable production.The results will provide technical support for seeking better fertilizer type for vegetable field.This experiment includes two parts:(1)Different nitrogen fertilizer types with equal nitrogen input and 20%reduction treatment for Pakchoi planting.(2)Different nitrogen fertilizer types with equal nitrogen input and reduction 20%treatment for Chinese cabbage planting.The study was conducted from October 2018 to July 2020 in Changshu Agro-Ecological Experimental Station,Chinese Academy of Sciences.A total of six seasons of leafy vegetables were planted,including two Chinese cabbage planting seasons and four Pakchoi planting seasons.According to local fertilization practices,the conventional nitrogen application rate is 200 kg N·hm-2 per season.A total of eight experimental treatments were set in this experiment:(1)Traditional urea fertilization treatment(N200),(2)Nitro compound fertilizer treatment(N200A),(3)Urease inhibitor(NBPT)urea treatment(N200B),(4)Partial substitution of organic fertilizer(urea:organic fertilizer=7:3)treatment(N200C),(5)Reduction of 20%urea treatment(N160),(6)Reduction of 20%+Jinzhengda controlled release fertilizer(N160D)(7)reduction of 20%+Meinong controlled release fertilizer(N160E),(8)No fertilization treatment(CK).NH3 volatilization,N2O emission,soil moisture content,soil temperature and vegetable yield were measured to evaluate the active gaseous nitrogen emissions of different experimental treatments.The main results are as follows:(1)The average yield of N200,N200A.N200B,N200C,N160,N160D and N160E were 27.20 t·hm-2,34.03 t·hm-2,31.46 t·hm-2,30.84 t·hm-2,25.89 t·hm-2,34.81 t·hm-2 and 31.29 t·hm-2,respectively.The yield of N200A was increased by 25.13%,the yield of N200B and N200C were increased by 15.68%and 13.41%,respectively.Compared with N200,the yield of N160 was decreased by 4.82%.The yield of N160D and N160E increased by 27.98%and 15.04%,respectively(Pakchoi);The average yields of N200,N200A,N200B,N200C,N160,N160D and N160E were 38.84 t·hm-2,47.29 t·hm-2,40.05 t·hm-2,43.74 t·hm-2,32.73 t·hm-2,47.62 t·hm-2 and 44.89 t·hm-2,respectively.The yield of N200A,N200B and N200C were 68.22%,9.79%and 39.59%,respectively(Chinese cabbage).This is consistent with the trend of experimental results in Pakchoi planting under the same treatment,and N200A has the highest yield benefit.Compared with N200,the yield of N160 was reduced by 49.33%.The yield of N160D was increased by 70.91%,and the yield of N160E was increased by 40.83%.This is consistent with the same treatment in Pakchoi planting test results trend,N160D’s yield increase efficiency reached the highest.(2)The average NH3 volatilization coefficients of N200,N200A,N200B,N200C,N160,N160D and N160E treatments were 11.22%,0.84%,2.28%,5.12%,6.54%,2.43%and 0.72%,respectively.The NH3 volatilization coefficient of N200 was the highest,and the NH3 volatilization coefficient of N200A treatment was the lowest(Pakchoi);And on the Chinese cabbage field,The average NH3 volatilization coefficients were 13.7%,2.5%,5.4%,6.1%,11.0%,3.2%and 1.4%.The NH3 volatilization coefficient of N200 treatment was the highest,and that of N160E treatment was the lowest(Chinese cabbage).The average cumulative emissions of N2O from open field Pakchoi of N200,N200A,N200B,N200C,N160,N160D and N160E were 1.20 kg·hm-2,0.49 kg·hm-2,0.63 kg·hm-2,0.88 kg·hm-2,0.73 kg·hm-2,0.58 kg·hm-2 and 0.61 kg·hm-2,respectively.Among them,N200A had the best emission reduction effect with the emission reduction coefficient reaching 59.26%,followed by N160D,which was 51.86%.The average cumulative emissions ofN200、N200A、N200B、N200C were0.44 kg·hm-2、0.09 kg·hm-2、0.19 kg·hm-2、0.30 kg·hm-2.N200A had the best emission reduction effect,the emission reduction rate was 73.51%.The average cumulative emissions of N2O treated with N160,N160D and N160E were 0.32 kg·hm-2 0.22 kg·hm-2 and 0.09 kg·hm-2,respectively.N160E had the best emission reduction effect,reaching by 77.83%,and the emission reduction rate of N160D was 56.30%,which was consistent with the same treatment results in Pakchoi.(3)The emission reduction effect of urease inhibitor treatment is moderate aas well as the cost.However,due to the unstable composition of urease inhibitor treatment fertilizers,there is no commercial mass production on the market,and it is difficult to promote on a large scale.The effect of organic fertilizer replacement treatment is poor but the cost is the lowest.There are many brands and influencing factors of organic matter.And thus it is difficult to control the amount of nutrients in the field management.Nitro compound fertilizer treatment has high yield increase rate and excellent emission reduction effect,which is a good choice.The technical goal of reducing application and increasing efficiency is achieved.But taking into account the further reduction of emission reduction targets,slow controlled release fertilizer will have greater advantage,if deeper optimization research conducted and reduced the cost of the slow controlled release fertilizer.(4)Selecting suitable slow-release fertilizer for nitrogen reduction and replacement treatment can obtain better effect of reducing fertilizer and increasing efficiency.Compared with Jinzhengda slow-release fertilizer,the emission reduction effect of Meinong slow-release fertilizer was better,due to the increase of phosphorus content.Therefore,better emission reduction and efficiency effect can be obtain through optimizing the ratio of nitrogen,phosphorus and potassium in fertilizer in future.In the actual production,farmers prefer the fertilizer with long-term fertilizer effect which can reduce the frequency of fertilization.Therefore,Meinong controlled-release fertilizer is a good choice. |
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