Synergistic effects of phosphogypsum and wheat varieties on saline–sodic soil properties and wheat productivity in Ethiopia

Soil salinity and sodicity are major constraints, limiting nutrient availability, degrading agroecosystems, and threatening agricultural productivity. In Ethiopia, most irrigated lowland areas are affected by salinity and/or sodicity, which sharply reduces crop yields. Addressing this problem requires effective and timely management strategies. Field and pot experiments were conducted on saline–sodic soils at the Metehara Sugar Estate during the 2022/23 and 2023/24 growing seasons to evaluate the synergistic effects of phosphogypsum (PG) application and wheat varieties on selected soil physicochemical properties and wheat performance. Factorial combinations of PG rates and wheat varieties were tested using a completely randomized design for pots and a randomized complete block design for field trials, each with three replicates. Soil samples were collected before soil amendment and after harvest to assess changes in physicochemical properties. Application of PG significantly improved wheat growth, physiology, and yield, as well as soil properties. The most effective rates, 150% and 200% of the gypsum requirement (GR), reduced soil pH from 8.16 to 7.93–7.91 and lowered exchangeable sodium percentage (ESP) from 34.3% to 11.0–7.9%. Applying PG alone at 150% or 200% GR rate, or growing the salt-tolerant wheat variety ETBW-5879, enhanced physiological traits such as relative water content, chlorophyll SPAD content, photosynthesis, and transpiration. Application of PG at 150 or 200% GR, combined with the salt-tolerant variety ETBW-5879, resulted in superior performance in terms of plant height, leaf area, above-ground dry biomass, and grain yield. At PG 200% GR, ETBW-5879 increased grain yield by 107% over untreated Gambo and by 224% over untreated Dande’a, while at PG 150% GR, the increases were 103% and 217%, respectively. Even application of PG at 100% GR with ETBW-5879 produced a grain yield that was 6% higher than PG at 200% GR with Gambo and 21% higher than PG at 200% GR with Dande’a. These results indicate that applying PG at 150% GR in combination with ETBW-5879 optimizes wheat yield on saline–sodic soils at Metehara. However, further validation across other saline–sodic soils and multi-year field trials in Ethiopia is necessary to draw robust conclusions.