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

Abstract

AbstractSlow 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 (Kfs) 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 Kfs 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 Kfs of the top 20‐cm soil layers. Compared with uncropped plots, Kfs 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 Kfs of the 0‐ to 20‐cm (with and without gypsum) when compared with wheat straw or fallow treatments. The Kfs on plots with alfalfa plus gypsum were significantly greater to 80 cm than the Kfs 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.