Effects Of Aeration Irrigation On Nitrogen Metabolism And Photosynthate Accumulation And Distribution In Grape

Xinjiang is an important forest and fruit industrial base in China.By the year 2016,Forests and fruit orchards has exceeded 1.30 million hectares in the Xinjiang Region.These areas are an important pillar of the region's social and economic development.The Xinjiang Region has an arid-and semi-arid climate.Agricultural production in the region is restricted by low rainfall amounts and a shortage of fresh water for irrigation.Therefore,research about high efficiency water-saving technology has important theoretical as well as practical significance to the region.This study is based on subsurface drip irrigation?SDI?with tanks that was designed by our research team.Solar powered aeration equipment through SDI with tanks was designed,and the reliability of the technology and the related technical principles were verified by the test.The results provide a theoretical basis for the application and popularization of the integrated technology of"water and fertilizer and gas"based on SDI with tanks.The contents of this study are summarized as follows:1.The new aeration irrigation system was first tested to determine its influence on grape growth and development.The results showed that the system increased root,branch,leaf,and total biomass by 11.20%?13.59%?22.95%and 14.43%,respectively,compared with the control.The system also reduced drought stress and increased leaf chlorophyll,net photosynthesis,and fluorescence within the same irrigation period.However,aeration irrigation reduced instantaneous water use efficiency of leaves,and had no water saving effect at the level of individual leaves.Aeration irrigation significantly increased?i?root growth in the 20–40 cm soil depth,?ii?nutrient absorption,?iii?new root growth,and?iv?root vigor during the grape growing season.The activities of SOD,POD,and CAT were also higher in the aeration irrigation treatment than in the control.This result indicated that aeration irrigation reduced and retarded the process of membrane lipid peroxidation.2.Carbon isotope tracer technique was used to study the effects of aeration irrigation on photosynthate distribution,soil respiration and soil enzymes activity.The results showed that aeration irrigation increased C allocation and transport to new branches,fine roots,and thick roots.This result suggested that aeration irrigation promotes the accumulation of photosynthates in the root system.Within the same irrigation period,aeration irrigation can significantly influence the soil O₂ content and the CO₂ content in the rhizosphere.Soil respiration initially increased and then decreased across the growing season.Soil respiration was greater in the aeration irrigation treatment than in the control.Aeration irrigation also increased soil urease and catalase activities at both the 20–30 and 40–50 cm depths.3.Aeration irrigation increased soil Olsen-P and available K and promoted decomposition of organic matter in the 20–30 cm soil depth.Aeration irrigation increased bacterial populations related to nitrification?i.e.,Nitrosospira?,P and K transformations?i.e.,Pseudomonas and Bacillus?and denitrification?i.e.,Ralstonia?.This meant that increased N,P,and K absorption by grape in the aeration irrigation system may be due to increases in bacterial populations related to nitrification and the mineralization of P and K.Aeration irrigation increased the populations of aerobic bacteria such as Nitrospirae but reduced the population of anaerobic bacteria such as Planctomycetes.Furthermore,analysis of the Chao1and Shannon indexes revealed that aeration irrigation significantly altered microbial community abundance but had little effect on bacterial community diversity.At the phylum level,aeration irrigation significantly?p<0.01?increased the abundance of Actinobacteria by16.7%and Nitrospirae by 22.7%compared with the control in the 40–50 cm soil depth.Canonical correspondence analysis?CCA?and correlation analyses showed that soil pH,Olsen-P,and NO₃-N were important indicators of bacterial community structure in the aeration irrigation system.4.¹⁵N tracer techniques were used to determine the effect of aeration irrigation on?i?grape growth and?iii?the absorption,distribution,and utilization of NH₄-N and NO₃-N.The results showed that aeration irrigation increased new shoot growth and stem diameter.Especially large increases were noted in the dry matter accumulation of new shoots and fine roots.Comparing within the same irrigation period,aeration irrigation increased leaf SPAD values and net photosynthetic rates,but reduced the instantaneous water use efficiency of the grape leaves.The ¹⁵N tracer showed that in the aeration irrigation treatment,new organs had greater ability to absorb and utilize NO₃-N than NH₄-N.The results showed that aeration irrigation did not affect the nitrate preference?i.e.,NH₄-N:NO₃-N uptake ratio?of grape.The results also showed that aeration irrigation significantly promoted NO₃ absorption and inhibited NH₄-N absorption.This suggests that NO₃-N should be selected as the N source for grapes in this aeration irrigation system.5.Soil NH₄-N at 10 d after irrigation was 28.95%greater in the aeration irrigation treatment compared with the control.Similarly,aeration irrigation also significantly increased soil nitrification potential at 20 d after irrigation.Soil NO₃-N contents in all of the aeration irrigation treatments were significantly less than that in the control.Soil dehydrogenase activity increased significantly at 20 d after irrigation,significantly earlier than the increase in the control treatment.Correlation analysis showed that soil catalase activity was significantly positively correlated with soil NO₃-N content?r=0.969?.Soil dehydrogenase activity was also positively correlated with soil nitrification intensity?r=0.907?.Overall,aeration irrigation can promote soil N transformation and perhaps the uptake of NO₃-N by grape roots.The increase in soil dehydrogenase activity may delay the decline in root vitality during the late growing season.6.¹⁵N-labeled urea was used to investigate the effect of rhizosphere aeration on plant growth and the absorption,distribution and utilization of fertilizer N in‘Red Globe'grape seedlings.The results indicated that the aeration irrigation significantly reduced the N derived from fertilizer?Ndff?in grape seedlings compared with the control.The two treatments also exhibited significant differences in the distribution of ¹⁵N among plant organs.The exception was that there was no difference between the treatments in the amount of ¹⁵N in grape leaves.The ¹⁵N fertilizer use rate was significantly less in the aeration irrigation treatment?3.46%?compared with the control?9.63%?.Overall,the results showed that aeration irrigation reduced the ability of grapes to absorb urea N and altered this N distribution among plant organs.This result indicated that aeration irrigation and urea application did not have synergistic effects.7.Comparisons were made to determine the effect of N fertigation amount on grape growth in the aeration irrigation system.The results showed that aeration plus N fertilizer not only increased leaf chlorophyll,actual PS II photochemical efficiency and photochemical quenching coefficient?qP?but also maintained the activities of SOD,POD,CAT and other antioxidant enzymes at high levels.Analysis of grape leaves in the aeration irrigation treatment showed that the N2 treatment could increase the net photosynthesis rates of grape leaves.Furthermore,the activities of SOD,POD,CAT and other antioxidase enzymes were higher in the N2 treatment than in the N1 and N3 treatments.Among the N treatments,N2also had the greatest root surface area,root volume,root length,and root tip number.The NH₄-N and NO₃-N contents in both leaves and roots were greatest in N2.Finally,nitrate reductase and glutamine synthetase activity were also highest in N2.The results showed that the fertilizer amount in N2 was optimal for grape growth in the aeration irrigation system.In the control treatment,grape growth was better in N3 than in either N1 or N2.The above results show that aeration irrigation has greater effect than N fertilizer amount on grape growth and the nitrogen concentration in plant growth is not better under the condition of gas injection,but a suitable range is needed.The best treatment was aeration irrigation plus N2.8.The results of field experiments in 2016 and 2017 showed that the aeration irrigation can increase growth of grape shoots and the diameter of stems,increase leaf chlorophyll,and significantly increase berry weight and tranverse diameter,cluster weight,and yield.However,aeration irrigation had no significant influence on berry color,soluble solid content,hardness,or the sugar:acid ratio of grape.Aeration irrigation delayed the development of berry color.The above results show that as a new technology,aeration irrigation can promote grape growth.However,grape is a perennial crop and its physiological metabolism is complex.To improve fruit quality,additional information is needed about the timing and frequency of aeration irrigation.Information about the related mechanisms would promote the application and popularization of this technology.