Gaseous Nitrogen Emission Under Variable Water And Nitrogen Input In Solar Greenhouse System In Losses Plateau

Solar greenhouse is an intensive crop production system in China,involving overuse of water and nitrogen?N?fertilizer,which results in the waste of valuable resources,and causes environmental problems such as gaseous nitrogen emission,nitrate accumulation and leaching.The nitrification process in the soils of Loess Plateau is rapid,as a result the large amount of organic and inorganic nitrogen fertilizer input in the solar greenhouse is quickly nitrified.At present,few studies focus on the gaseous nitrogen emission caused by N fertilization in solar greenhouse system in this area.In order to clarify the characteristics of gaseous emission under different water and N input,four water and N treatments were selected in this study,which includes:no N input plus common irrigation,famer N input plus common irrigation,optimum N input plus common irrigation and optimum N plus optimum irrigation.The ammonia?NH₃?and nitrous oxides?N₂O?emission of different water and N treatments were monitored by closed chamber intermittent ventilation and static chamber-gas chromatography,respectively.The whole greenhouse was taken as the research object,and the active sampling method was used to be measured the NH₃volatilization rate of the vents during the greenhouse ventilation period,and the following conclusions were obtained.?1?Nitrogen transformation in solar greenhouse was quick,NH₃ volatilization showed rapid increase soon after the fertilizer were applied.N input increased NH₃ volatilization rate,and NH₃ volatilization peak appeared on the 1 to 2 day after fertilization ranged from0.26 to 2.02 kg N·ha^-1·d^-1,and lasted for about 7 days.The cumulative of NH₃volatilization from N input treatments was 2.82⁸.18 kg N·ha^-1,with an emission factor of0.58%³.45%.The cumulative NH₃ volatilization from N input treatment was significantly higher than no N input treatment,except for optimum N input plus optimum irrigation treatment,and there was no significant difference observed between both N input treatments.Decrease in the irrigation volume caused increase in the cumulative NH₃ losses under the same N application rates,and the average amount increased by 46.7%in both seasons.The cumulative NH₃ volatilization decreased by 24.7%with decrease in the nitrogen application rate compared with the conventional nitrogen input treatment.The average of all the observations of NH₃ volatilization rate and cumulative NH₃ volatilization in watermelon season were higher than tomato season.The soil NH₄⁺-N content,soil moisture,soil and air temperature had a significant influence on NH₃ volatilization,and high temperature promoted ammonia emissions in watermelon season.?2?The N₂O emission patterns of different seasons were similar,and the emission peaks appeared 1 to 4 days after fertilization.N application significantly increased the N₂O emission flux.The peak of N₂O emission in different seasons were 1.29×10^-32.93×10^-3kg N·hm^-2·d^-1.and N₂O emission lasted for about one week.The cumulative N₂O emission from N input treatments in different seasons ranged 0.61².68 kg N·ha^-1,with an emission factor of 0.39%⁰.85%.The cumulative N₂O emission of N input treatment was significantly higher than no N input treatment except for optimum N input and common irrigation treatment.The cumulative N₂O emission on average decreased by 43%compared with famer N application after decrease in the nitrogen input,while the cumulative N₂O emission increased under the same N input after decrease in the irrigation volume.The factors like soil temperature,air temperature,soil moisture,soil NH₄⁺-N and NO₃^--N content were all significantly positively correlated with N₂O emission flux.?3?Considering that the solar greenhouse is a semi-closed system with high temperature and humidity,and since NH₃ is easily soluble in water,therefore the NH₃emission has been different from the field and the vent,in order to reasonably evaluate the NH₃ loss in the solar greenhouse system.Active sampling method was used for two consecutive seasons to monitor the NH₃ rate of the greenhouse vent,and the NH₃volatilization differences between the field and vent were compared.The results showed that the peak of NH₃ appeared on the first day after fertilization,and lasted for about 7 days,and the volatilization peaks were in the range of 0.63².96 kg N ha^-1·d^-1.The NH₃volatilization rate in different seasons were 0.050⁰.419 kg N·ha^-1·d^-1,the NH₃concentration of the gas emission from the vent is different,and the average were 0.018and 0.056 mg·m^-3,the cumulative NH₃ emission from whole vent were 2.13 and 3.35 kg N·ha^-1 in tomato and watermelon seasons respectively,cumulative NH₃ emission from N input treatments in different seasons was 5.41²1.83 kg N·ha^-1,and the cumulative NH₃emissions in the whole greenhouse accounted for 15.3%³9.4%of the overall proportion of cumulative emission from N input treatments.The NH₃ volatilization in the whole vent was significantly lower than the NH₃ volatilization on the field.Therefore,while calculating the gaseous loss of N in the solar greenhouse,the information about of the internal environment of the facility should be considered.