| In order to meet the increasing demand of vegetables,facility vegetable planting has developed rapidly in the last 40 years in China.However,in order to obtain high yield of vegetables,farmers blindly adopt a management mode of large-scale fertilization and frequent irrigation,which directly leads to the waste of water and nitrogen resources and environmental pollution.The study was conducted in a greenhouse of Dawei village,Xinmi,Zhengzhou City.Two irrigation methods [drip irrigation(DF),border irrigation(BF)] and three nitrogen treatment levels(high nitrogen 100%,medium nitrogen 75%,low nitrogen 50%)were set up,incompletely combined to four treatments(DF100,DF75,DF50 and BF100),plus two additional treatments [medium water and high nitrogen in drip irrigation(T2),low water and high nitrogen in drip irrigation(T3)].Six different water and nitrogen treatments were carried out to study,to study the effects of different water and nitrogen management on soil water and nitrogen distribution,nitrogen deep transport and cucumber growth.In addition,the fuzzy comprehensive evaluation method was used to analyze the optimal water and nitrogen management,which can provide the theoretical basis for the sustainable development of facility cucumber.The main conclusions are as follows:(1)Under the traditional water and nitrogen management mode in experimental area,the application rate of water and nitrogen far exceeded the normal growth demand of cucumber.This in turn inhibits the growth of cucumber to a certain extent,and is a potential threat to the soil and groundwater environment;(2)The traditional irrigation method of large-water irrigation in the experimental area is nearly 50% more than that of drip irrigation,but it does not show obvious advantages.It can be seen that the drip irrigation mode can achieve high-efficiency and water-saving under the premise of ensuring the normal growth demand of cucumbers.About the recommended nitrogen application rate in the experimental area,it should be reduced by at least half of the traditional nitrogen application rate of 4.5 kg/ha?d,that is,the nitrogen application rate for low nitrogen treatment;(3)Under the water and nitrogen management mode of the experimental area,the leaching loss of nitrogen in the soil is large,and the leaching rate is 2m/a within 8m.For the irrigation area of the Yellow River where the experimental area is located,the shallow groundwater is generally distributed at a depth of 30 m.Under the current water and nitrogen management mode,the pollution of leaching nitrogen to this aquifer is expected;(4)There is no significant difference in crop yield between the different water and nitrogen treatments set up in the experiment.Therefore,high-yield and high-water does not necessarily have high output,and high output does not necessarily have high net income;(5)The local cucumber planting water use efficiency is low,even the best one,the third-season drip irrigation treatment also has nearly half of the water infiltration loss,and only twenty to thirty percent of the water is effectively used in the irrigation treatment.Consider about the apparent utilization of nitrogen fertilizer and the partial productivity of nitrogen fertilizer,the optimal water and nitrogen management mode is DF50(drip irrigation and low nitrogen)treatment;(6)The study uses the fuzzy comprehensive evaluation method to consider the economic benefits,quality benefits and environmental benefits of the cucumber planting under four different water and nitrogen management modes.Finally,it is concluded that treatment DF50(drip irrigation with low nitrogen)is the best choice,which has good economic benefits and little impact on soil and groundwater,under the premise of ensuring that there is no significant difference in cucumber quality. |
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