Influences Of Ground Cloth Mulching On The Root-zone Soil Moisure,Temperature,and Water Consumption Of Citrus In The Ridged Citrus Orchard

Citrus is widely planted in the southern China,where rainfall is abundant but seasonal distribution is highly uneven.The difficulty of water management in orange orchards and the low water use efficiency of citrus trees are the main problems limiting the development of light and efficient cultivation techniques for citrus.Ground cloth mulching and monopoly planting can improve the soil environment,store water and retain moisture,realize the inter-seasonal use of water,and facilitate the moisture management of orange orchards,so these two measures are widely used in citrus orchards.However,the effects of ground cloth mulching and monopoly planting on the dynamic distribution of water and temperature in the root zone soil profile,on the growth of citrus branch tips and water utilization are not clear.There is a lack of long-term high-frequency dynamic observation of soil water and heat in citrus orchards,which limits the precise application of soil drip irrigation in citrus orchards.In this paper,a continuous dynamic observation study of field meteorology-root zone soil-fruit tree was conducted in 2021 with a citrus orchard on a gently sloping yellow-brown soil developed in Quaternary red clay soil.The ridging planted citrus orchard set ground cloth mulch and bare surface(control)withsitu high-frequency observations of moisture and temperature in the root zone soil profile.Then the root distribution characteristics,citrus branch tips growth,photosynthetic indexes and canopy temperature was observated to analyse soil moisture and temperature changes,of the soil moisture dissipation patterns under drip irrigation,rainfall infiltration and post-rainfall and citrus water consumption characteristics.And The soil moisture and temperature changes in the root zone of southern citrus were clarified.Then the effect of ground cloth mulching on soil moisture,temperature and water consumption of citrus in monopoly orchards was investigated.The main research results are as follows.(1)Ridging planting effectively regulated soil moisture conditions in the root zone of citrus.Ridging planting significantly affected soil moisture at 20-50 cm depth in the citrus orchards,but not at shallow(0-10 cm depth)and deep(50-70 cm depth)levels.Ridging planting took advantage of the height difference between monopoly furrows to drain away part of the rainfall during rainfall,reducing the probability of soil moisture accumulation in the root zone(mid-monopoly position)of citrus;.In contrast,monopoly planting maintained soil moisture conditions in the root zone during no rainfall events.(2)Ground cloth mulching reduced soil water storage in the root zone,but increased soil temperature,changing the vertical profile of soil moisture and temperature,with the effect on soil temperature mainly at 0-20 cm depth.The degree of influence of ground mulch on soil moisture and temperature was summer > spring > autumn > winter,and the gradient of vertical change of soil moisture underground mulch showed an increasing type.In contrast,it showed a decreasing type under control.As the depth of soil layer deepens,the influence of ground cloth mulching on soil moisture and temperature gradually decreases.(3)The effect of rainfall on soil moisture infiltration and soil evaporation was weakened by ground cloth mulching.The corresponding degree differed under different rainfall patterns in different seasons.After drip irrigation,the ground cloth mulch reduced the accumulation of irrigation water in the soil layer.Its infiltration depth was only 50 cm compared with the control 1h infiltration depth(70 cm),which slowed down the infiltration rate of drip irrigation.The interception of rainfall by ground mulch increased with increasing rainfall,with 37.14 %,48.91 % and 62.64 % of rainfall intercepted by ground mulch under medium,heavyrainfall conditions,respectively,compared to the control.Ground mulch reduced soil water storage by 58.7 % and 4.3 % at 0-20 cm depth in spring and summer,respectively,while no significant difference was observed in autumn and winter.(4)Ground cloth mulching limited the root growth of citrus and its photosynthetic utilization efficiency,but effectively improved the growth status of citrus branches.The total root length(4333 cm)of citrus trees under ground cloth mulch decreased by 14.22 %compared to the control.The ground cloth mulching reduced the net photosynthetic rate and water use efficiency of citrus by 3.39% and 19.70%,respectively,but improved the stomatal conductance and transpiration rate of 9.43% of the new shoot leaves of citrus trees by 3.26%.In summer and autumn,the growth rate and length of citrus shoots under ground cloth mulch were higher than those in ground cloth mulch.(5)Although the ground cloth mulching increased the water consumption of the citrus tree,it ultimately improved the water use efficiency of the citrus branches.Ground cloth mulching mainly increased the water consumption of citrus trees by 76.8% and the water consumption intensity by 76.6% in summer,while there was no significant difference between spring and autumn.In summer,the water use efficiency of branches under ground cloth mulch(0.22 mm/mm)was about 1.29 times that of the control treatment(0.17 mm/mm),and in autumn,there was no significant difference between the water use efficiency of branches mulched by ground cloth and the control.