The Effect Of Water-fertilizer Coupling Under Drip Fertigation On The Growth And Yield Of Greenhouse Nectarines In Sandy Area Of Northern Shaanxi

Based on the present situation of drought and water shortage in the sandy area of Northern Shaanxi,where the protected fruit trees owned low fruit quality with inefficient water and fertilizer utilization,this paper took greenhouse nectarine as trial material and conducted a two-year water-fertilizer coupling experiment under drip fertigation,which provided a theoretical basis for scientific and rational irrigation and fertilization of protected nectarine in this area.The experiment was conducted at Jinshawan Agricultural Cooperative of Yuyang District in Yulin,Shaanxi Province?38°18?N,109°43?E?,from February 5,2017 to June 15,2018.Three irrigation upper limits were set in the experiment,W1?90%?_f?,W2?75%?_f?and W3?60%?_f?,irrigation event began together when the soil moisture content of any treatment approached the lower limit of 50%?_f?field water holding capacity?;three NPK fertilization levels were also set:F1?130%F2?,F2(N 200 kg·ha^-1+P₂O₅ 120 kg·ha^-1+K₂O 240 kg·ha^-1),F3?70%F2?,which were completely combined,the local irrigation and fertilization method?CK?was set as the contrast.The effects of different irrigation and fertilization levels on nectarine tree growth,yield,fruit quality,water and fertilizer use efficiency and nutrient absorption were studied,the results showed that:?1?The effect of irrigation level on the growth of nectarine shoots under drip irrigation was significant?P<0.05?,which was positively correlated with irrigation amount.Irrigation and fertilization levels and their coupling effects could have significant or extremely significant effects on chlorophyll content or SPAD in leaves?P<0.01?,and the rules were different at different growth stages.During the critical period of fruit growth,the chlorophyll content of leaves under different water and fertilization treatments was significantly different?except at the end of the second fruit expansion stage in 2018?.At the end of the second fruit expansion stage,irrigation amount had a significant effect on leaf chlorophyll content or SPAD.W2 increased the chlorophyll content of leaves in 2017,while the SPAD value of leaves at W1 level was the largest in 2018,followed by W2.The chlorophyll content and SPAD value of nectarine tree leaves increased with the processing growth period.?2?Appropriate irrigation level W2?75%?_f?promoted the increase of nectarine yield,but a higher irrigation amount had little effect of yield increase or even made a decrease.And,a poor irrigation amount could significantly reduce fruit yield.Under a certain amount of irrigation,the fruit yield of moderate fertilization level F2(N 200 kg·ha^-1+P₂O₅ 120 kg·ha^-1+K₂O 240 kg·ha^-1)was the highest.Excessive or low amount of fertilization resulted in yield decline.Irrigation and fertilization coupling effect influenced the fruit yield significant and extremely significant in 2017 and 2018,respectively. W2F2 could maintain high yield in the two year experiment,its average yield,water use efficiency?WUE?and partial fertilizer productivity?PFP?were 29633.8 kg·ha^-1,26.5 kg·m^-3,52.9kg·kg^-1,respectively.Compared with CK treatment,W2F2 could averagely reduce water and fertilizer consumption by 3595 m3and 200 kg per hectare,it also increased fruit yield8813 kg per hectare with an increase rate of 42.3%.By fitting optimization with the non-linear least squares method,the irrigation and fertilization ranges based on the target of high yield,water and fertilizer saving were 750-900 m³·ha^-1 and 510-610 kg·ha^-1.The corresponding yield,WUE and PFP ranges were 25139-26760 kg·ha^-1,31.5-34.4 kg·m^-3,44.8-48.2 kg·kg^-1,separately.?3?Under the drip fertigation,the content of soluble solids and anthocyanin in fruits was increased by appropriate irrigation and fertilization level compared with CK,and the content of organic acid in fruits was increased by water stress.A high or little fertilization amount could reduce the Vc content,and the Vc content increased with the increase of irrigation at F2fertilization level in 2017.Compared with the fruit quality of different treatments,W2F2owned preferable fruit quality in the two year experiment,and its single fruit weight was higher than others in 2018 meaning better economic value.The TOPSIS method was used to evaluate the quality of fruits,the top three treatments were W2F2,W3F2 and W3F1 in 2017;however,W2F2,W1F3 and W2F1 in 2018.The fruit quality of W2F2,W3F1 and W1F3 were better in both experimental years.?4?The level of irrigation and fertilization and their coupling effect could significantly affect the contents of total nitrogen,total phosphorus and total potassium in leaves,and showed different rules with the change of growth period.At the end of the first fruit expansion stage and the beginning of the pit-hardening period stage,high irrigation amount increased the nitrogen content of leaves but decreased the total potassium content.The total phosphorus content in leaves was extremely significantly affected by irrigation level?P<0.01?at the end of the first fruit expansion stage,and low irrigation and fertilization level caused the smallest mean value.From the end of the first period of fruit expansion to the 40 days after fruit harvest,the total nitrogen content of fruit increased first and then decreased,while the total potassium content reached the maximum value at the end of the second period of fruit expansion,while the total phosphorus content decreased obviously with the development of growth period.Adequate application of water and fertilizer was the necessary guarantee for high yield,nitrogen is the main factor affecting yield,followed by potassium.When the N,P and K nutrient accumulation amount of mature fruit were used as the independent variables,the optimal linear regression relationship with yield could be obtained.