Hydraulic Conductivity of Saline‐Sodic Soil after Gypsum Application and Cropping

Abstract

Abstract Slow internal drainage is a major problem in the reclamation of saline‐sodic soils. This field experiment was conducted on a low‐permeability, saline‐sodic soil (a fine‐loamy, mixed, thermic Typic Natrustalf) near Lahore, Pakistan, to compare field‐saturated hydraulic conductivities ( K fs ) after various treatments. Treatments were: (i) deep‐rooted perennial alfalfa ( Medicago sativa L.), (ii) sesbania [ Sesbania bispinosa (Jacq.) W.F. Wright]‐wheat ( Triticum aestivum L.)‐sesbania rotation, (iii) incorporated wheat straw at 7.5 Mg Ha −1 , and (iv) a fallow control. These four treatments were each combined with and without 25 Mg ha −1 of gypsum, subsoiling to 0.45 m, and open‐ditch drainage. The K fs of the soil under each treatment was measured in each 20‐cm increment to 120 cm after 6 mo and 1 yr. Gypsum applications increased the K fs of the top 20‐cm soil layers. Compared with uncropped plots, K fs of the 0‐ to 20‐cm depth on cropped plots with gypsum increased about twofold after 6 mo and about fourfold after 1 yr. The crop rotation significantly increased the K fs of the 0‐ to 20‐cm (with and without gypsum) when compared with wheat straw or fallow treatments. The K fs on plots with alfalfa plus gypsum were significantly greater to 80 cm than the K fs on fallow plots. Neither subsoiling nor open‐ditch drains improved soil permeability. Gypsum plus sesbania‐wheat‐sesbania rotation most increased permeability of the surface layer; gypsum plus alfalfa was best to improve the permeability of the deeper layers.