Solute transport in a loamy soil under subsurface porous clay pipe irrigation

Subsurface porous clay pipe irrigation is widely considered to be a very promising method for small-scale irrigation in arid regions. Unfortunately, salt accumulation at and near the soil surface using this method may affect germination of direct-seeded crops. Predicting salt movement and accumulation with clay pipe irrigation will allow producers to anticipate the need for leaching to control salinity in the soil root zone. The HYDRUS-2D model was used to simulate the accumulation of salt from a subsurface clay pipe irrigation system, installed at 30 cm depth, during the growing season of okra (Abelmoschus esculentus) irrigated with water having a salinity of 1.1 dS m−1. The loamy soil profile had an initial salinity of 2.3 dS m−1. Predicted electrical conductivity (ECe) values at the end of the growing season correlated significantly (R2 = 0.952) with measured saturated paste ECe data obtained at the end of the field experiments. Salinity was found to be relatively low around the pipes, but increased with distance away from the pipes. Measured and predicted soil salinity levels were especially higher above the clay pipes. Our results indicate that proper management of salt accumulation is vital for sustainable crop production whenever subsurface irrigation systems are being implemented.