The effect of crop residue cover and soil texture on crusting

[摘要] Large areas of cultivated soils throughout the world develop rainfall-induced soil crusts.The soil crusts are usually the cause of reduced seedling emergence. To have quantitativeinformation on the factors influencing the development of surface crusts and on theinfluence of ameliorating treatments on crust strength is valuable.The objectives of this study were firstly, to determine the influence of soil texture on thesusceptibility of different soils for crusting; secondly, to quantify the effect of soil crustson the emergence of wheat, sorghum, soybean and sunflower; and thirdly to determinethe optimum level of crop residues that can be used as a mulch to mitigate the effect ofsoil crust strength.Five soils ranging in texture from sand to loam were sampled from the surface (0 - 200mm). The soil samples were used in four greenhouse pot experiments that wereconducted to examine the effect of crust strength on seedling emergence. Separate potexperiments in the greenhouse were conducted to determine how particle size distributionwas related to soil crust strength.Regression analyses showed that silt, silt plus clay and clay contents were related to cruststrength as indicated by modulus of rupture, penetration resistance and emergence force.All the relationships were of third order polynomial nature. The crust strength increasedinitially with increasing silt plus clay contents up to about 35 to 40 %, or clay contents upto about 25 %, then declined as a result of cracking that occurred upon drying.The emergence of wheat, soybean and sunflower was little affected at crust strengths lessthan 0.7 Mpa or 500 gf when measured as penetration resistance and emergence forcerespectively. Above these values seedling emergence decreased linearly with increasingcrust strength.Large areas of cultivated soils throughout the world develop rainfall-induced soil crusts.The soil crusts are usually the cause of reduced seedling emergence. To have quantitativeinformation on the factors influencing the development of surface crusts and on theinfluence of ameliorating treatments on crust strength is valuable.The objectives of this study were firstly, to determine the influence of soil texture on thesusceptibility of different soils for crusting; secondly, to quantify the effect of soil crustson the emergence of wheat, sorghum, soybean and sunflower; and thirdly to determinethe optimum level of crop residues that can be used as a mulch to mitigate the effect ofsoil crust strength.Five soils ranging in texture from sand to loam were sampled from the surface (0 - 200mm). The soil samples were used in four greenhouse pot experiments that wereconducted to examine the effect of crust strength on seedling emergence. Separate potexperiments in the greenhouse were conducted to determine how particle size distributionwas related to soil crust strength.Regression analyses showed that silt, silt plus clay and clay contents were related to cruststrength as indicated by modulus of rupture, penetration resistance and emergence force.All the relationships were of third order polynomial nature. The crust strength increasedinitially with increasing silt plus clay contents up to about 35 to 40 %, or clay contents upto about 25 %, then declined as a result of cracking that occurred upon drying.The emergence of wheat, soybean and sunflower was little affected at crust strengths lessthan 0.7 Mpa or 500 gf when measured as penetration resistance and emergence forcerespectively. Above these values seedling emergence decreased linearly with increasingcrust strength.

[发布机构] University of the Free State