Evaluating the effect of phosphogypsum on selected soil properties, and morpho-physiology, yield and phosphorus use efficiency of wheat varieties under saline-sodic soil

Abstract

Salt-affected soils constrain agricultural productivity, particularly in Ethiopia’s irrigated lowlands, where salinity and sodicity severely reduce crop yields. Effective reclamation strategies are therefore essential. This study evaluated the effects of phosphogypsum on soil properties, wheat morphophysiology, yield, and phosphorus-use efficiency under saline-sodic conditions at Kessem Sugar Estate. A factorial pot experiment was conducted during the 2022/23 and 2023/24 cropping seasons using different phosphogypsum rates and wheat varieties. Soil analysis before amendment and after harvest showed that phosphogypsum application markedly improved soil properties. The highest phosphogypsum rate (200% GR) reduced soil pH from 8.45 to 7.93 and exchangeable sodium percentage from 26.5% to 6.9%, while increasing exchangeable Ca, available P, and sulfate by 60.2%, 74.1%, and 159.8%, respectively. Combining 150% or 200% GR phosphogypsum with the salt-tolerant wheat variety ETBW-5879 produced the highest panicle length, seeds per spike, relative-water-content, grain yield, transpiration rate, P uptake, and P-use efficiency. Similarly, phosphogypsum at 150% and 200% GR and the ETBW-5879 variety significantly improved plant height, leaf area, chlorophyll content, biomass yield, photosynthetic rate, and water-use efficiency. Grain yield of ETBW-5879 was substantially higher than that of Gambo and Dande’a under untreated soil conditions, by 294% and 536% at 200% GR, 273% and 502% at 150% GR, and 184% and 358% at 100% GR, respectively. Even at 100% GR, phosphogypsum with ETBW-5879 produced 28% and 87% higher grain yields than phosphogypsum with Gambo and Dande’a, respectively. Overall, ETBW-5879 consistently outperformed the other varieties across phosphogypsum rates. The combination of phosphogypsum at 150% GR with ETBW-5879 was the most effective treatment for improving wheat yield under saline-sodic conditions. However, field validation across diverse saline-sodic environments, including assessment of potential phosphogypsum-impurities, is recommended before large-scale adoption.