Study On The Macropore Flow Characteristics Of Sugarcane Soil In Karst Region Of Guangxi

Fragile geological environment has adverse effect on agricultural production,in the karst region of Guangxi.It is important to explore deeply the influence of different tillage measures on soil structure and study the soil macropore flow characteristics in karst region for appropriate crop planting and water and soil conservation of land.Based on field dyeing tracer method,interior CT scan imaging method and mathematical statistics analysis method,the change characteristics of macropore flow under different tillage treatment were revealed systematically in sugarcane field of karst region in Guangxi.Meanwhile,the research studied macropore characteristics that included macropore morphology and macropore space structure,and analyzed main factors that influenced macropore flow formation.The main results were as follows:(1)There were some differences in the macropore flow dyed pattern between no-tillage and tillage.In the vertical direction,the staining area ratio,uniform flow infiltration depth and the macropore flow ratio of the no-tillage were greater than of the tillage.In horizontal direction,the staining area ratio of no-tillage and tillage respectively presented the "wave model","middle gathered type" distribution pattern.The development of macropore flow in soil under the no-tillage was higher than under the tillage.(2)Through CT scanning technology,the spatial structure characteristics of soil macropore were obviously different among different tillage treatments.The soil pore area density in the tillage area was greater than in the no-tillage area in the same soil depths;The trend of soil pore area density(0-10 cm)was higher than soil pore area density(30-40 cm)in different soil depths of no-tillage.The rangeability of soil pore complexity was greater in the no-tillage than in the no-tillage tillage.The means of macropore number,macropore porosity,curvature,and connectivity in the tillage area were greater than in the no-tillage area,except macropore ratio surface area.To some extent,the tillage could improve soil porosity and pore connectivity and enhance soil permeability.(3)Macropore flow was a complicated process of soil water movement,and its formation and development were influenced by many factors.Sand,silt,clay,silt clay ratio,organic matter,total phosphorus,the density of root weight and the number root holes were associated with formation of macropore flow.Those factors were significantly associated with macropore flow in sugarcane field of no-tillage,but correlation significantly declined in the tillage area,especially organic matter and total phosphorus content,number of root holes and density of root weight.Those factors could be divided into three principal components to affect the formation of macropore flow in the no-tillage area and in the tillage area,but the component was different.In no-tillage area,the first principal component reflected the plant biomass(density of root weight,number of root holes and diameters of root length density)and chemical substance(organic matter,total phosphorus)in the soil,but the first principal component of tillage area only reflected plant biomass(density of root weight,root length density)in the soil.The second principal component of the no-tillage area and the tillage area was different in the number of root holes and silt.The third principal component of the notillage area reflected the compactness of the soil,which was obviously different from the third principal component(nutrient and water condition)in tillage area.Tillage treatment could affect the formation of macropore flow so that the main influence factors of macropore flow were plant biomass and chemical substance in the no-tillage area,but the main influence factor of macropore flow only was plant biomass in the tillage area.