| Aiming at the problems of high nutrient inputs,low nitrogen utilization,and serious losses in facilities melon production in Hebei Province,firstly the characteristics of nutrient inputs and nitrogen leaching loss from facilities melon systems were clarified through field investigation and sampling of representative sheds.On this basis,a typical facilities melon production area was selected to carry out a field experiment,thus the characteristics of plant nitrogen absorption and utilization,nitrogen leaching and gaseous losses under the control measures of nitrogen reduction combined with nano-carbon sol were explored,and the nitrogen management and nano carbon sol regulation measures for preventing and controlling nitrogen losses from facilities melon system were constructed,which provided scientific theoretical basis and technical support for reducing nitrogen losses and improving nitrogen fertilizer utilization efficiency and high-efficiency nitrogen regulation of facilities melon production systems in Hebei province.The main results are as follows:(1)In the main production areas of facilities melon in Hebei Province,the amount of nutrient inputs was very large,which was applied mainly in the form of organic fertilizers and thus there was large nutrient surpluses.The total nutrient inputs of N,P2O5,and K2O reached 729.24,340.47,and 699.41 kg/hm2,and the nutrient surpluses of N,P2O5,and K2O reached 526.87,231.88,and 427.94 kg/hm2,respectively.(2)There was a large amount of available nutrients accumulated in the 0-30 cm soil layer of facilities melon production areas in Hebei Province,and the surplus nitrogen in the soil showed an obvious leaching trend.The cumulative amount of Avail-N was 467.80 kg/hm2,and the cumulative amount of soil NO3-N below 60 cm depth which accounted for 39.77%～50.04%.The average accumulation amount of Olsen-P and Avail-K in the 0-30 cm soil layer was 336.63 kg/hm2 and 1120.06 kg/hm2,respectively.Further cluster analysis of soil nutrient accumulation status in seven main facilities melon production areas in Hebei Province was divided into four levels.Qingxian and Yongqing were considered as the heavy nutrient accumulation areas,Raoyang and Laoting were high nutrient accumulation areas,Qingyuan and Anci were the moderate nutrient accumulation areas,and Xinle was the suitable nutrients accumulation area,respectively.(3)The recommended nitrogen application and the combined application of nitrogen and nano-carbon sol can ensure the stable yield of facilities melons and significantly improve the quality of facilities melons.Compared with the traditional nitrogen application,the recommended nitrogen application(with 30%reduction of the traditional nitrogen application amount)and the combined recommended nitrogen and nanocarbon sol application can significantly increase the content of vitamin C and soluble solids of the facilities melon,and the ratio of fruit to solid acid,respectively,whose increase rates were 4.13%～40.91%,17.99%～19.45%,and 29.75%～46.51%,respectively.At the same time,it can also significantly increase the apparent nitrogen utilization rate and the partial productivity of nitrogen fertilizer,and the increase rates were 27.15%～61.81%and 30.58%～41.82%,respectively,which has a certain promoting effect on the improvement of economic efficiency.(4)The recommended nitrogen application and the combined application of recommended nitrogen and nano-carbon sol can significantly reduce the loss of nitrogen leaching and decrease the risk of soil salinization.Compared with the traditional nitrogen application,recommended nitrogen application and combined application of recommended nitrogen and nano-carbon sol can reduce the average NH4+-N content in the 30-120 cm soil profile by 12.92%～32.70%and the NO3-N content by 14.31～20.92%,respectively.In addition,the average accumulation of NO3-N in 0-120 cm soil profile was decreased by 12.82%～27.53%,and the content of soil salt segregants also decreased by 12.18%～23.71%.(5)Recommended nitrogen application and combined application of recommended nitrogen and nano-carbon sol can significantly reduce nitrogen gaseous losses(N2O emission and NH3 volatilization).Compared with the traditional nitrogen application,the recommended nitrogen application and the application of recommended nitrogen and nano-carbon sol can reduce soil N2O emission flux and cumulative N2O emission by 32.13%～50.76%and 29.70%～51.05%,respectively.The soil NH3 volatilization rate and the cumulative NH3 volatilization amount were also reduced by 23.92%～39.10%and 22.75%～35.29%,respectively,and the total nitrogen gaseous losses was reduced by 34.94%～56.11%.Comprehensive evaluation,recommended nitrogen combined with nano-carbon sol application(nitrogen fertilizer at the application rate of 350 kg N/hm2,nano-carbon sol at the rate of 240 L/hm2)was an effective regulation measures to reduce nitrogen losses and increase nitrogen utilization efficiency in facilities melon production which could achieve a win-win situation for both the economy and the environment. |
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