Effect Of Water-fertilizer-gas Coupling Subsurface Drip Irrigation On The Growth Of Tomato In Greenhouse

With the increase of China’s population and the development of industry and agriculture,the shortage of agricultural water resources is getting prominent,and the available agricultural water is decreasing year by year.Therefore,the development of efficient agricultural water technology has become an inevitable choice.Subsurface drip irrigation has significant advantages in crop water and nutrient utilization efficiency,and is an important facility to developing water-saving agriculture.However,studies have shown that subsurface drip irrigation suppresses the air in the soil while supplying water to crops,and crop roots are in an anaerobic environment for a long time after irrigation,which is easy to cause insufficient oxygen supply to crop roots.In order to solve the rhizosphere hypoxia caused by drip irrigation and improve the utilization efficiency of water and fertilizer,this study took greenhouse tomato as the experimental object,whose roots were more sensitive to soil hypoxia,and adopted the orthogonal experimental design to set up a total of 12 treatments,including 3 fertilization levels（high,medium and low fertilization levels are represented by D₁,D₂,D₃,respectively）,4aeration levels（non-aeration,high aeration,medium aeration,low aeration by A₀,A₁,A₂,A₃）,3 irrigation levels（low,medium and high irrigation water volume is represented by I₁,I₂,I₃,respectively）.By analyzing the effects of different water-fertilizer-gas coupling treatments on tomato growth index,dry matter accumulation,photosynthetic index,rhizosphere environment,yield and quality,and water use efficiency,an efficient water-fertilizer-gas coupling irrigation mode was proposed for greenhouse tomato.The main results are as follows:（1）Water-fertilizer-gas coupling subsurface drip irrigation promoted the growth and root activity of greenhouse tomato.The most important factor affecting tomato plant height and stem diameter was aeration level.The plant height increased with the increase of aeration amount and irrigation amount,and the stem diameter increased with the increase of irrigation amount.The plant height and stem diameter of tomato under aeration treatment increased by 5.4%and9.7%compared with non-aerated treatment.Among all the treatments,the plant height and stem diameter of aerated tomato were increased by 14.2%and 15.4%compared with non-aerated tomato.The aeration had the greatest effect on the root activity at flowering and mature stage,and the fertilizer rate had the greatest effect on the root activity at fruit expansion stage.In same irrigation and fertilization treatment,the root activity of aerated treatment was 47.2%and 2.9%higher than non-aerated treatment at fruit setting stage and fruit expansion stage,respectively.The root activity of aerated treatment was 56.5%,24.3%and 24.4%higher than non-aerated treatment at fruit setting stage,fruit expansion stage and mature period,respectively.（2）Water-fertilizer-gas coupling subsurface drip irrigation increased chlorophyll content and dry matter accumulation of greenhouse tomato.The effects of three factors on chlorophyll content were in the order of aeration amount,irrigation amount and fertilizer amount.P_n,T_rand G_s of aeration treatment were 17.9%,43.4%and 35.7%higher than those of non-aeration treatment under the same irrigation amount and fertilizer amount.Among all treatments,P_n,T_r,C_iand G_s of aeration treatment were 37.2%,45.3%,1.9%and 55.2%higher than those of non-aeration treatment,respectively.High aeration rate,high irrigation rate and high fertilizer rate were beneficial to the dry matter accumulation of greenhouse tomato,and the dry weight of shoot under high and medium fertilizer treatments increased with the increase of aeration rate.Under the same irrigation and fertilization treatment,the chlorophyll content of aeration treatment was increased by 7.6%compared with that of non-aeration treatment.Among all the treatments,the chlorophyll content in aeration treatment was 14.3%higher than that in non-aeration treatment.（3）Water-fertilizer-gas coupling subsurface drip irrigation significantly increased soil enzyme activity and soil microbial population.The results showed that under the same irrigation and fertilization treatment,soil catalase activity and soil urease activity increased by 5.4%and10.8%respectively in aeration treatment compared with that without aeration treatment.The number of bacteria,actinomycetes and fungi in rhizosphere soil increased by one time,47.5%and 64.5%,respectively.Among all the treatments,aeration treatment increased soil catalase activity by 7.8%,soil urease activity by 17.9%,and soil alkaline phosphatase activity by 6%compared with non-aeration treatment.The number of bacteria,fungi and actinomycetes in rhizosphere soil increased by 1.1 times,0.95 times and 48.1%.（4）Water-fertilizer-gas coupling subsurface drip irrigation improved tomato quality,yield and water use efficiency.The effects of the three factors on tomato yield were as follows:aeration amount,fertilizer amount and irrigation amount.The yield of tomato increased with the increase of aeration.The contents of soluble solids,soluble sugar,vitamin C and soluble protein in aerated tomato were 12.4%,15%,18%and 26%higher than those in non-aerated tomato,respectively,and the yield was increased by 20%.The effects of the three factors on WUE of tomato were as follows:aeration amount,irrigation amount and fertilizer amount.The WUE of tomato increased with the increase of fertilizer application.The WUE of tomato was the highest under high aeration,followed by medium aeration and no aeration,and the lowest under low aeration.The WUE of tomato decreased with the increase of irrigation amount.Considering different water-fertilizer-gas coupling treatment on greenhouse tomato growth characteristics,accumulation of dry matter,root activity,photosynthesis characteristic,rhizosphere soil microbial number,root zone soil enzyme activity,yield and quality,and water use efficiency,et al.The gas doping ratio was 17.25%,the fertilization amount was 180-90-112.5 kg/hm~2（N-P₂O₅-K₂O）,and the experimental treatment at K_cp was 0.75,which was the better water-fertilizer-gas coupling irrigation mode of the greenhouse tomato in this test.