Effects Of Different Irrigation And Fertilizer Levels On Fruit Quality And Antioxidant System And Soil Environment Of Tomato In The Greenhouse

Drought is the most important factor limiting plant establishment, growth anddistribution in many regions of the world. The loess hilly region is a typical semi-arid andarid region in northwest of China. The harsh environments and long-term anthropogenicdisturbance had resulted in severe soil erosion and water loss, vegetation degradation andfragile ecosystems. Due to economic and technique problems, fertilizer and soil water areapplied excessively in vegetable field. Therefore, The research on responses of vegetable ingreenhouse to water and fertilizer deficit conditions and their eco-physiological adaptationstrategies to drought environment in the loess hilly regions could provide insights into theimprovement of the soil water and fertilizer management, improved vegetable quality andyield.and therefore, are of great theoretical and practical significance.In this paper, tomato (Lycopersicon esculentum) which is plant widespread in theLoess hilly region in greenhouse was chosen as experimental material to study the effectsof water and fertilizer on fruit quality,yield and enenzy activity in fruit and leaves. Usingthe method of manual control experiments, a total of six treatments with three soil moisturelevels: water deficit (Wl,55%±5%of soil holding capacity), moderate irrigation (Wm,75%±5%of soil holding capacity), high irrigation (Wh,95%±5%of soil holding capacity)and two levels of fertilizer application: deficit fertilizer (Fl,420Kg·hm^-2N+294Kg·hm^-2P2O5+504Kg·hm^-2K₂O),and moderate fertilizer (Fm,600Kg·hm^-2N+420Kg·hm^-2P2O5+718Kg·hm^-2K₂O) were established. The following results were obtained.(1)The vegetables adaptation in Yangling is better than that in Yan'an and Yulin. The temperature in December and January can not meet the cucumber, tomatoes fruit vegetablenormal growth and development needs in Yan'an and Yulin. Therefore, this period shouldbe mainly based on improving the greenhouse temperature. Some measures such ascovering straw mat at night, wiping the dust on the films and other insulation measures canbe taken to increase the temperature of greenhouse. Since leafy vegetables can grow atlower temperature and accumulated temperature and have higher adaptability, thereforethese areas which have relatively poor heating conditions can plant leafy vegetables tomeet the needs of people in winter.(2)Soil moisture content was mainly affect by irrigation, not by nitrogen level. Thesoil water content in surface changed significantly. With the deeper of soil, the changingmagnitude of soil water content decreased. Irrigation mainly effected soil water content in0-40cm soil deepth. In the same fertilizer conditions, soil respiration increased with soilirrigation increased. In the same irrigation conditions, soil microbial activity and soilrespiration were inhibited with the amount of nitrogen reduction. The impact of differentwater and fertilizer on soil pH and was similar to EC. The change of pH and EC is less onthe vertical direction, but greater on the horizontal direction. Increasing fertilizer canincrease the soil conductivity. In the the same amount of fertilizer, soil electricalconductivity decreased with the increase of irrigation. The soil temperature have asignificant positive correlation with air temperature under different soil water and fertilizertreatment in different soil depths,and there had a significant negative correlation betweensoil moisture and soil temperature. With the increase in soil depth, the lag of soiltemperature became larger.(3)Different water and fertilizer treatments had significant effects on tomato yield.Tomato production increased with the increase of water amount, but fruit quality and wateruse efficiency decreased. Tomato yield increased with the increase of fertilizer amount.Tomato fruit quality had significant positive correlation with drought. Deficit irrigationimproved fruit quality. However, excessive irrigation decreased the Vc content of fruit. Inthe same fertilizer conditions, the Vc content in tomato fruit increased with reduction ofirrigation amount; In the same water levels, the content of soluble sugars, organic acidsdecreased.with the increase in the amount of fertilizer.(4)Under water deficit, SOD, POD, CAT and APX activity rised in tomato. The CAT activity and SOD activity was higher in deficit irrigation, while the POD and APXactivity was higher in moderate deficit irrigation. Moderate amount of nitrogen fertilizercan increase the activity of antioxidant enzymes in leaves. Fertilizer levels had notsignificantly affect on POD, APX activity in the leaves, but had significantly affect onSOD, CAT activityï¼›Fertilizer levels had significantly effect on SOD, POD, CAT, APXactivity in fruits. The APX in fruit maintained a high level, to protect the fruit againstoxidative damage, while the SOD, POD, CAT activity was lower. Fruit quality has asignificant positive correlation with antioxidant enzyme activity. Deficit irrigationimproved fruit quality, but also increased the concentration of free oxygen.Therefore, different fertilizer and irrigation had significant effects on fruit quality,antioxidant systems and the soil environment of tomato in the greenhouse. Under highirrigation, the lag effect of soil temperaturet increased with the increase amount of fertilizer.Under deficit irrigation, the lag effect of soil temperature decreased the increase amount offertilizer. The changes of pH and EC were small in the vertical direction while large in thehorizontal direction. Under drought stress conditions fruit plants resist drought stress bydecreasing the content of fruit moisture, increasing soluble sugars, organic acids, solubleproteins and other macromolecules to increase the permeability, and enhancing antioxidantenzyme activity. Tomato fruit increasing the non-enzymatic antioxidants and antioxidantenzymes activity together to protect tomato from drought stress. Therefore, from the pointof increasing in tomato yield and quality, reducing the free oxygen ion concentration,improving water use efficiency view, the treatment75±5%of soil holding capacity and600Kg·hm^-2N+420Kg·hm^-2P2O5+718Kg·hm^-2K2O is the optimal combination.