Modeling water retention capacity and hydraulic properties of a manure-amended loam soil and its effect on wheat and maize yield

Water retention capacity and hydraulic conductivity of different soil layers is needed to quantify plant available water that may help determine irrigation water use efficiency (WUEi) and yield of different crops. A field from Experimental Area of Soil and Environmental Sciences, University of Agriculture, Faisalabad was selected to quantify water retention curve (WRC) of the soil and other soil hydraulic properties and manure amendment under two irrigation levels was evaluated for this purpose. Soil water retention and hydraulic conductivity was measured at different suitable matric potentials using pressure membrane apparatus and tension infiltrometer, respectively. Curves of soil water retention and hydraulic conductivity were obtained by power function, Van Genuchten-Maulem and Durner-Maulem models. Durner-Maulem model was best in predicting the water retention and hydraulic conductivity of soil under field conditions. The highest available water capacity of soil with 14.2% increase at 0-35 cm soil depth was observed in manure amended soil, while least was recorded at 35-70 and 70-110 cm soil depths with lower soil organic carbon and increased sand proportion. Manure application increased the WUE_i of wheat and maize crop by 40.5 and 39.0% under deficit irrigation (M₅₀I₁), which ultimately increased the yield of these crops by 40.1 and 38.6%, when compared to "M₀I₂". Application of manure with deficit irrigation "M₅₀I₁" was better choice than applying heavy irrigation with no manure "M₀I₂".