Effects Of Lower Limit Of Soil Moisture And Depth Of Subsurface Irrigation Pipes On Growth And Development Of Pepper

Aiming at the problems of extensive irrigation methods and low water use efficiency of vegetable grown in field in the irrigation area of the Yellow River diversion in Ningxia,four lower limits of soil moisture were set in each growth period of pepper(seedling stage,blossom and fruit stage,full fruit stage and later fruit stage):W1(55%θf 75%θf,65%θf,75%θf),W2(55%θf,75%θf,75%θf,65%θf),W3(65%θf,75%θf,65%θf,75%θf),W4(75%θf,75%θf,75%θf,75%θf),and set three buried depths of subsurface irrigation pipe:D1(0 cm),D2(10 cm),D3(20 cm).The effects of lower limit of soil moisture and the depth of subsurface irrigation pipe on growth and water use efficiency of pepper were studied through experiments.The water consumption characteristics and distribution of soil water in all growth periods and stages of pepper were analyzed.The suitable lower limit of soil water and buried depth of subsurface irrigation pipe for growing pepper in field in this area were determined.It provides theoretical basis for improving water use efficiency of pepper in Ningxia irrigation area with Yellow River diversion.The main results are as follows:(1)Under the same lower limit of soil moisture,the soil moisture content of 0～10 cm soil layer was:D2>D3>D1,and that of 10-20 cm soil layer was:D3>D2>D1.The deeper the subsurface irrigation pipe was buried,the higher the soil moisture content in horizontal direction;Under the condition of the same buried depth of the subsurface irrigation pipe,the lower limit of soil moisture at each stage had a greater impact on the soil moisture content of 0-40 cm soil layer,and a smaller impact on the soil moisture content of 40～60 cm soil layer.(2)The water consumption under different buried depths of subsurface irrigation pipe was:D 1>D2>D3,but the buried depth of pipe had little influence on the water consumption of pepper,and the difference in water consumption is small;the water consumption under different lower limit of soil moisture was:W4>W2>W3>W1,the lower limit of soil moisture has a significant effect on the water consumption of pepper,and the lower the lower limit of soil moisture,the lower the water consumption of pepper.The daily water consumption intensity and water consumption modulus in each growth period of pepper were:full fruit stage>later fruit stage>blossom and fruit stage>seedling stage.Among them,the water consumption modulus reached 32.31%,26.03%,21.99%and 14.33%respectively.(3)Compared with D1 and D2 treatments,D3 treatment can significantly promote the growth of plant height,stem diameter,leaf area index,dry matter accumulation and harvest index of pepper under the same lower limit of soil moisture.Under the same buried depth of subsurface irrigation pipe,plant height,stem diameter,leaf area index and dry matter content of W4 treatment with the highest water lower limit in each growth period were all at the highest level,and lower soil water lower limit significantly inhibited the growth of pepper in seedling and full fruit stage,but had no significant effect on the growth index of hot pepper in later fruit stage.In addition,the lower limit of soil moisture at seedling stage was 55%θf.It can significantly improve the capsicum harvest index up to 0.694.(4)Compared with D1 and D2 treatments,the pepper yield and water use efficiency of D3 treatment increased by 1.18%～8.46%and 1.34%～11.02%under the same lower limit of soil water.D3 W4 treatment had the highest yield of pepper,38177.73 kg/hm2,but there was no significant difference with D3W2 treatment.The water use efficiency and irrigation water use efficiency of D3W2 treatment were the highest,which were 10.71 kg/m3 and 14.08 kg/m3 respectively,which had significant difference with other treatments.Through field test and analysis,it is shown that the buried depth of local subsurface irrigation pipe is 20 cm,and the lower limit of soil moisture in seedling stage,blossom and fruit stage,full fruit stage and later fruit stage were 55%θf,75%θf,75%θf,65%θf,respectively.It is more conducive to the growth and development of pepper.This irrigation mode provides technical guidance and theoretical basis for efficient and water-saving planting of field pepper in the irrigation area of the Yellow River diversion in Ningxia.