Effects Of Irrigation Threshold And Lateral Depth On Growth, Yield And Quality Of Tomato In Solar Greenhouse

Subsurface drip irrigation is a new irrigation technology for efficient water saving,which can effectively reduce the inefficient evaporation of the surface and improve the water use efficiency of the plant.As the main agricultural facilities for cultivation of vegetables in the north,it has been in a semi-closed state for a long time.Over-irrigation is widespread.The process not only causes waste of water resources,but also breeds pests and diseases.It is not conducive to the improvement of vegetable yield and quality.Irrigation water is the main source of moisture required for vegetables in the sunlight greenhouse.The development of reasonable irrigation technology and precise technical parameters could produce the appropriate conditions of water,fertilizer,gas and heat to increase the absorption capacity of soil moisture and nutrients for vegetables and the use of efficiency,so as to further obtain higher yields and economic benefits.In order to explore the mutual feedback mechanism of tomato growth and water distribution in the sunlight greenhouse in Guanzhong area and the effective way to improve the water use efficiency,this paper conducted a drip irrigation experiment in the solar greenhouse,we analyzed the effects of different irrigation thresholds and lateral depths on distribution and consumption of water,root system and dry matter distribution,yield and quality.The main results showed as follows:(1)The average soil water content and the water consumption of tomato were mainly affected by the irrigation threshold.The increase of lateral depth could increase the location of the greatest soil water content,lateral depth had a greater effect on soil water content in 0~10 cm and in 20~40 cm soil layer,and had a less affected in 50 ~ 60 cm soil layer.Lateral depth had a significant influence on water consumption of tomato(p<0.05),and the lateral depth of 10~20 cm increased the water consumption of tomato under mild(75% of field capacity)and moderate-mild water deficit(60% of field capacity).(2)The increase of lateral depth reduced the root distribution in 0~20 cm soil layer and promoted the root growth in 20~60 cm soil layer,and the distribution of root had the characteristics of concentration distribution around the location of lateral depth.Lateral depth had a significant effect on the root system growth in 0~10 cm,20~30 cm,30~40 cm soil layer and had no significant effect on the root growth of 50~60 cm soil layer(p>0.05).The root length and root surface area of tomato fine root(d <1 mm)and coarse root(d >1 mm)were significantly affected by irrigation threshold,but the lateral depth only had a significantly effect on the root length and root surface area of fine root.Mild water deficit and the lateral depth of 20 cm were favorable for the root length and surface area growth of fine roots,and the proportion of coarse roots was reduced.Mild water deficits and the lateral depth of 20 cm were more favorable for total dry matter accumulation,while 75% of field capacity could increase fruit dry matter allocation,and the lateral depth of 20 cm could promote dry matter to stems and leaves and reduce the distribution ratio of root dry matter.(3)After planting at 58~78 days(from flowering and fruit setting last phase to the early fruit),lateral depth had the biggest influence on the growth of tomatoes,the lateral depth of 20 cm is more conducive to growth of tomato plant height and stem diameter.Irrigation threshold had a significant influence on the fruit weight and horizontal diameter of tomato and the lateral depth had a significant effect on the fruit weight of tomato.The fruit weight and horizontal diameter of tomato showed an increase first and then a decrease with lateral depth increased.The ratio of A grade fruit(D?7.5 cm)was significantly affected by irrigation threshold,and increased with the increase of irrigation threshold,but the increase of irrigation threshold could increase the ratio of C grade fruit(D<6.5 cm).the lateral depth of 20 cm increased the ratio of A and B grade fruit(6.5 cm?D<7.5 cm)under mild and moderate-mild water deficit.(4)Irrigation threshold had a significant impact on the soluble solids,vitamin C and sugar/acid ratio of tomato,the lateral depth of 20 cm decreased tomato quality,but there was no significant influence of lateral depth on soluble sugar,vitamin C and organic acid.The changing trend of yield and irrigation amount of tomato showed an increase first and then a decrease with lateral depth increased.When the lateral depth was 20 cm,the yield of tomato was higher and the water consumption was larger.The water use efficiency of tomato decreased significantly with the increase of irrigation threshold,and lateral depth had no significant impact on the water use efficiency.Based on the consideration of the plant height,yield and water use efficiency of tomato,the lateral depth of the 20 cm and 60% field capacity would be the most appropriate treatment combination for tomato cultivation in the sunlight greenhouse in Guanzhong region of Shaanxi Province.