Application of compost and gypsum to improve physicochemical properties of saline-sodic soil conditions in Asaita District, Northeastern Ethiopia

Soil salinity and sodicity are important constraints to agricultural productivity in irrigated areas of the Lower Awash Basin, particularly in Asaita District, Northeastern Ethiopia. This study evaluated the effectiveness of biological and chemical-organic reclamation approaches for improving the physicochemical properties and nutrient availability of saline-sodic soils at two experimental sites in Asaita District. Two field experiments were conducted separately. The first experiment evaluated nine treatments comprising salt-tolerant forage species with and without 10 t/ha filter-cake compost, while the second experiment evaluated three gypsum rates (0, 5, and 10 t/ha) combined factorially with three filter-cake compost rates (0, 5, and 10 t/ha). Both experiments were arranged in a randomized complete block design with three replications. Soil pH, electrical conductivity (EC), exchangeable sodium, exchangeable sodium percentage (ESP), bulk density (BD), organic carbon (OC), total nitrogen (TN), cation exchange capacity (CEC), available phosphorus (Av. P) and available sulphur (Av. S), and selected micronutrients were determined after treatment application. The results showed that integrated amendment treatments generally produced greater improvements in soil properties than individual amendments. At Site I, Blue panic grass (Panicum antidotale) combined with 10 t/ha filter-cake compost produced the lowest BD (1.01 g/cm³) and pH (7.77), compared with 1.31 g/cm³ and 8.32, respectively, in the untreated control. At Site II, the combined application of 10 t/ha gypsum and 10 t/ha filter-cake compost was the best-performing treatment. It reduced EC from 6.56 to 2.85 dS/m (56.6%), ESP from 13.17% to 5.79% (56.0%), and pH from 8.25 to 7.65 (0.60 pH units; 7.3%), while reducing BD from 1.37 to 1.01 g/cm³ and increasing CEC from 73.2 to 79.6 cmolc/kg. The same treatment also enhanced the availability of several nutrients and micronutrients. These findings indicate that integrated application of gypsum and filter-cake compost can effectively improve saline-sodic soil properties under the conditions of the experimental sites. Therefore, 10 t/ha gypsum combined with 10 t/ha filter-cake compost is recommended as the best-performing treatment for saline-sodic soils with similar characteristics in Asaita District, provided that adequate irrigation and drainage are available. The findings should not be generalized to the entire Afar Region because soil properties, irrigation conditions, and agro-ecological characteristics vary among locations.