Fertilization Status And Fertilizer Reduction Potential Of Tomato Cultivated In Solar Greenhouse

Solar greenhouses,as an important facility vegetable cultivation way in the north of China,have developed rapidly since the 1980s,and farmers’households for high economic benefit,the phenomenon of large water and fertilizer in solar greenhouses is relatively common,there are a large number of high cultivation years in the cultivation area of typical solar greenhouses,and its soil accumulates a large amount of nutrients without reasonable use,which causes the waste of nutrients and limits the development of cultivation industry in solar greenhouses.Therefore this study is intended to focus on the current fertilization status of cultivation at facilities located in Yangling and Jingyang of Shaanxi Province,and evaluate the fertilizer reduction potential of the investigated regions.At the same time,field experiments were conducted in the Yangling Demonstration Area,a typical daylight greenhouse in the Yangling Demonstration Area of Shaanxi Province,and the effects of different water and nitrogen treatments（divided into no nitrogen application+conventional irrigation,conventional nitrogen application+conventional irrigation,optimized nitrogen application+conventional irrigation）on crop yield,nitrogen carrying out capacity and nitrogen use efficiency in solar greenhouses were investigated in the hope of providing the basis for rational fertilization for farmers.The main conclusions obtained from the study are as follows:（1）The average total nutrient inputs for N,P₂O₅,and K₂O in the daylight greenhouse of Yangling were 1151,1042,and 1080 kg/hm²,which were 3.8,8.7,and 2.5times higher than the average nutrient carrying by the crop,respectively,and decreased by 334 kg/hm²（22.5%）,338 kg/hm²（24.5%）,and 279 kg/hm²（20.5%）in comparison with the statistics of 2011-2012;The annual apparent nutrient surplus reached 848.45,925.97,and 646.64 kg/hm² for NPK,respectively;The problem of excess nutrient input is alleviated but still serious compared with before;The ratio of total nutrient input was 1:0.90:0.94,and the ratio of phosphorus to potassium nutrient input was too high;The average rate of total nutrients applied to single stubble tomato plants in the daylight greenhouse was 876 kg/hm²,788 kg/hm² and 808kg/hm² using N,P₂O₅ and K₂O,respectively,and the three nutrient excesses of N,P and K for tomato nutrients in the daylight greenhouse reached 74.1%,100%,75.2%and 67.8%,86.7%,61.3%,respectively,which showed great potential for nutrient depletion.（2）The average total N input for N,P₂O₅ and K₂O in the daylight greenhouse of Jingyang was 2122.23,1791.7 and 1952.41kg/hm²,which were 3.6,9 and 2.8 times the crop nutrient carrying out,respectively;The annual apparent nutrient filling margins of N,P and K reached 1534.75,1593.5,and 1257.97 kg/hm²,which were 2.6,8,and 1.8 times of the nutrient carrying capacity,respectively,indicating a serious nutrient input deficit;The ratio of total nutrient input was 1:0.84:0.92,and the ratio of phosphorus to potassium nutrient input was too high;All 0-900 cm soil nitrate nitrogen accumulations in greenhouse grown around 15 and 25 years were around 3500 kg/hm²,which was numerically equal to the apparent nitrogen filling margin of greenhouse in 2-3 years,indicating a possible water management problem in local greenhouse;The exceedance of nitrate nitrogen in local ground water is up to 77.8%,with an average content of 24.2 mg/L,which has been seriously contaminated by nitrate nitrogen.（3）The results of a field experiment with different water and nitrogen treatments for eight consecutive crops during five years showed that no significant differences were observed in yield,biomass,or total N carrying capacity among treatments,indicating that appropriate water reduction for nitrogen control will not affect the yield and N carrying capacity of the crop.From the eight season overall,the optimized nitrogen application could significantly improve the nitrogen use efficiency by 15.54%-16.65%compared with the conventional nitrogen application,and there was no significant difference between the two treatments,OPT+FI and OPT+OI,indicating that there is also potential for nitrogen reduction and water reduction.Both the no nitrogen treatment and the optimized nitrogen treatment reduced nitrate nitrogen accumulation in 0-200 cm soils significantly compared to the pre-test value,with a significant 43.9%reduction in the OPT+FI treatment compared to the pre-test value and a 51.45%reduction in the OPT+OI treatment compared to the pre-test value,indicating that continuous nitrogen control water reduction can effectively reduce nitrate nitrogen accumulation in greenhouse soils in solar greenhouses and does not affect crop yield.