Effects Of Different Cultivation Practices On Soil Water And Heat Characteristics And Their Responses To Rainfall In Banana Plantations Of Guangxi

The research of soil hydrothermal changes and its response to rainfall under different land use practices is beneficial to improve the hydrothermal wastage in banana cultivation in Guangxi region due to its extensive management pattern.According to the conventional cultivation pattern of banana in Guangxi,two treatments,dry land trenching(ST)and converting paddy fields to dry land through furrowing(DT),were set up.Based on the longterm monitoring of soil moisture and meteorological data in the experimental area and the analysis of thermal conductivity model to simulate the changes of soil thermal conductivity,this study explored the characteristics of soil moisture and thermal conductivity changes and spatial distribution characteristics,furthermore their responses to different rainfall types.The results indicate that:Throughout the study period the DT treatment had 1.49 times greater average soil water content and better water retention capability in 10-50 cm soil layer than that of ST treatment.The standard deviation of soil water content for different treatments showed a decrease with the increasing of soil depth,in which the DT treatment had a greater range of active depth and more active months for soil water.The thermal conductivity of all soil layers in the DT treatment were significantly greater than that in the ST treatment,especially for 20 cm soil layer,where the former was 26.2% higher than the latter.Moreover,the relatively stable soil temperature variation in the DT treatment was more favorable to the growth of banana roots.The degree of spatial variability of soil water content and thermal conductivity decreased with the increasing soil moisture for different land use practices.The exceeded 90% spatial correlation of soil water content was strong for both treatments under dry,wet and moderate moisture conditions.The spatial variability of soil water content was mainly caused by structural variability,such as precipitation played a major role.Soil thermal conductivity of both treatments showed moderate spatial correlation under dry and wet conditions,with spatial structure ratios ranging from 31% to 58.1%.However,it showed a strong spatial correlation under moderate moisture conditions.To a certain extent,the soils of both treatments had the ability to maintain the stability of spatial distributions for moisture and thermal conductivity,which was better in the DT treatment.Soil water content and thermal conductivity of both treatments responded significantly to rainfall.In the light rainfall intensity rainfall type,especially for rain type IV),the increase of surface soil water content in the DT treatment was 3.5 times greater than that in the ST treatment.In contrast,in the medium rainfall intensity rainfall type,the response of soil water content was more sensitive in the ST treatment.The synchronization of soil water content trends in different soil layers increased with increasing rainfall intensity.In the light rainfall intensity rainfall type,the averaged increase of soil moisture for all soil layers was 87.8% higher in the DT treatment than in the ST treatment.In comparison,in the heavy rainfall type,the averaged increase in soil moisture at the 20 and 40 cm soil horizons in the DT treatment was 2.6% and 8.9% lower than that in the ST treatment,respectively.It meant that rainfall intensity was one of the factors affecting the change of soil water content in deep.Soil thermal conductivity was higher in the DT treatment than in the ST treatment,except for rainfall type I.Similarly,the increase in soil thermal conductivity for both treatments was greatest when the rainfall was a heavy storm.In the light rainfall type,the averaged increase of soil thermal conductivity in the DT treatment was 9.6% higher than that in the ST treatment.However,the averaged increase for soil thermal conductivity in the DT treatment was 22.0% and 16.4% lower than that in the ST treatment for the 20 and 40 cm soil layers in the heavy rainfall type,respectively.Therefore,the variation in rainfall intensity had an effect on the response magnitude of soil thermal conductivity in deep soil.In summary,the converting paddy fields to dry land through furrowing is better than dry land trenching in improving and stabilizing soil water and thermal conditions,which could promote the soil water holding capacity and enhance water use efficiency.it suggests that the former land use practice contribute to the sustainable development of the banana cultivation in Guangxi.