Study On The Coupling Effect Of Water And Nitrogen On Apple Trees In Northern Shaanxi Under Surge-root Irrigation

The Loess Plateau in Northern Shaanxi is one of the main apple producing areas in China,but the level of water and nitrogen management in this area is low,and the apple yield and quality can not be guaranteed.In order to find out the best combination mode of water and nitrogen coupling for apple tree planting in mountainous area of Northern Shaanxi,this paper takes 7-year-old apple tree in mountainous area of Northern Shaanxi as the research object,adopts the completely randomized block design,and sets up three irrigation levels(full irrigation H1,light deficit irrigation H2 and heavy deficit irrigation H3)and three nitrogen application levels(high nitrogen N1,medium nitrogen N2 and low nitrogen N3)to study the effects of water and nitrogen coupling on physiological growth,yield,quality and water and nitrogen use efficiency of apple in mountain area under the condition of surge-root irrigation.The main results are as follows:(1)The water consumption of apple trees in different water and nitrogen treatments was significantly different.Under the condition of a certain soil moisture gradient,in the whole phenological period,the water consumption of N2 and N3 treatment was 10.14%and 20.45%lower than that of N1 treatment.Under the condition of a certain amount of nitrogen,the water consumption in the whole phenological period of H2 and H3 treatment was 3.36%and 6.18%lower than that of H1 treatment.The water consumption of apple trees in each phenological stage is as follows:fruit expansion stage>flowering and fruit setting stage>germination stage>fruit maturity stage.The increase of nitrogen application and soil moisture gradient increased the total water consumption of apple trees in the whole phenological period.(2)The new length and leaf area index of apple trees increased with the increase of water and nitrogen input,and the leaf area index and growth days of each treatment were in accordance with Richards model;moderate increase of soil moisture content and nitrogen application was beneficial to increase the number of flowering and fruit setting of apple trees;under the same irrigation level,apple fruit diameter and final volume increased with the increase of nitrogen application,and nitrogen application level was the same Under the condition of H2 treatment,the diameter and final volume of apple reached the maximum.There is an obvious phenomenon of "noon break" in photosynthesis of apple leaves.Net photosynthetic rate(PN),transpiration rate(TR),stomatal conductance(GS)decreased with the decrease of water and nitrogen input,intercellular CO2 concentration(CI)increased with the decrease of water and nitrogen input,carboxylation efficiency(CE)and instantaneous water use efficiency(LWUE)decreased with the decrease of water and nitrogen input.(3)The coupling of water and nitrogen has a significant effect on the yield,quality and water and nitrogen use efficiency of apple trees.The yield of H2 treatment was higher than that of H1 and H3 treatment,and the yield of N2 treatment was higher than that of N1 and N3 treatment under the condition of a certain soil water content gradient.The amount of irrigation had a extremely significant effect on the quality,hardness,color,soluble solid,titratable acid,soluble sugar and vitamin C content of apple single fruit(P<0.01)The content of titratable acid in fruit increased with the increase of water and nitrogen input,and the content of vitamin C in fruit increased with the increase of water and nitrogen input.Irrigation and nitrogen application had a extremely significant effect on NPFP(P<0.01),and the interaction between them had a significant effect on NPFP(P<0.05).Under a certain amount of nitrogen application,NPFP of H2 treatment was higher than that of Hl and H3 treatment,and NPFP of N3 treatment was higher than that of N1 and N2 treatment under a certain gradient of soil moisture content;moderate water deficit was conducive to improving water use efficiency of apple trees,Water consumption efficiency(CWUE)and irrigation efficiency(IWUE)of apple trees treated with H2N2 were the highest.(4)Under the same soil water content gradient,reducing the amount of nitrogen application reduced the contents of total nitrogen,alkali hydrolyzed nitrogen,nitrate nitrogen and ammonium nitrogen.Under the same nitrogen application level,the content of total nitrogen,alkali hydrolyzed nitrogen,nitrate nitrogen and ammonium nitrogen increased with the decrease of soil water content gradient,and the effect of nitrogen application amount on soil nitrogen content was more significant than that of irrigation.(5)The coupling effect of water and nitrogen of apple in the mountainous area of Northern Shaanxi under the condition of surge-root irrigation was evaluated by using the method of grey correlation degree and TOPS IS.The results showed that the soil moisture content was controlled at 70%?85%?f and the nitrogen application rate was 400 kg·hm-2 can improve the yield,quality,water use efficiency and nitrogen partial productivity of apple trees.It is the best range of soil water content and nitrogen application amount of apple trees in the mountainous area of Northern Shaanxi under the condition of surge-root irrigation.