Effect Of Nitrogen Application Rate And Nitrogen Application Time On Nitrate Of Cucumber,Celery And Soil Inorganic Nitrogen

In recent years,the excessive application of nitrogen fertilizer in facilities agricultural production has brought varying degrees of harm to the quality of vegetables,soil environment and groundwater sources.In view of the current safety hazards caused by overuse of chemical fertilizers and the pollution of soil environment caused by crops,cucumber and celery were used as test objects to study the effects of different nitrogen fertilizer application rates and different nitrogen supply time on nitrate and Nitrate content and the influence of soil inorganic nitrogen,and the change trend of nitrate in cucumber and celery under different storage conditions were tested to provide a theoretical basis for the rational application of nitrogen fertilizer in cucumber and celery production,ensuring product quality and safety,and controlling nitrate pollution.And I get the following result:(1)Nitrate and nitrite contents of celery were 7.4 and 2.2 times higher than those of nitrate and nitrite in the same nitrogen application rate.Nitrate and Nitrite content in the vigorous growth stage of the two crops was higher than that in the harvesting period.Under the experimental conditions,when the amount of nitrogen applied was120~600kg/hm~2,the nitrate and nitrite contents of cucumber were all within the range of national safe food consumption.When the amount of nitrogen applied reached480kg/hm~2 and 600kg/hm~2,the contents of celery nitrate and nitrite exceeded the qualified range and they are unfit for human consumption.(2)There was a linear positive correlation between the amount of nitrogen fertilizer applied and soil nitrate nitrogen content.When the nitrogen application rate was480kg/hm~2,600kg/hm~2,the content of nitrate nitrogen and ammonium nitrogen in the upper layer soil(0-40cm)increased with the increase of nitrogen fertilizer;in the deep soil layer(40-100cm),there was obvious nitrate status.Nitrogen accumulation,while no significant change in ammonium nitrogen.(3)When the nitrogen application rate was 120~480kg/hm~2,the cucumber and celery yield increased synchronously with the amount of nitrogen applied.The CK treatment yield was significantly lower than the fertilization treatment.When the nitrogen application amount reached480kg/hm~2and 600 kg/hm~2,the yield increase effect was not obvious or the production was reduced.Considering the output and all other quality factors in a comprehensive manner,under the conditions of this experiment,the optimum nitrogen application rate of cucumber and celery in greenhouses was 360kg/hm~2.(4)Stopping the supply of N fertilizer 10-15 days before harvest can effectively reduce the content of nitrate and nitrite in vegetables and has no significant effect on the yield.(5)Under different storage conditions,the nitrite content of vegetables at room temperature(25°C)was significantly higher than that at cold storage(4°C).However,no matter what kind of storage methods are used,"nitrification peaks"appear.Therefore,it is recommended to buy ready-to-eat food.If there is a need for storage,try to choose low-temperature storage,and do not store it for too long.