Salt and water dynamics of irrigated vertisols cultivated with fodder crop of Echinochloa stagnina in Niger River valley

Irrigating Vertisols to produce crops, such as rice, alters its hydrological regime and often degrades the soil, particularly through waterlogging and salinization. The objective of this study was to evaluate the effects of the fodder crop Echinochloa stagnina on the salt and water dynamics of saline vertisols, in comparison to an irrigated paddy system in the Niger River valley. The study was conducted in irrigated paddy fields in the Niger River valley, using an experimental design with four treatments: (i) submerged bare soil without crops (PT), (ii) soil cultivated with rice (PR) over two successive cropping seasons, (iii) soil cultivated with E. stagnina over two successive seasons (PEs) with a complete harvest in between, and (iv) soil permanently cultivated with E. stagnina (PEp) with staggered harvests. The results showed that water table fluctuations were positively correlated with soil salt stock, especially in deeper layers. The salt stock decreased significantly over time under irrigated E. stagnina crops. After 15 months, the initial salt stock decreased by 33 to 36% under E. stagnina crops, compared to only 4% under the rice crop and submerged bare soil in the 0 to 60 cm layer. Crop diversification in paddy systems, with the introduction of E. stagnina as a fodder crop, appears to be a promising agroecological approach for soil and water conservation by promoting soil desalination and ensuring the sustainability of irrigated paddy systems in Niger. Key words: Irrigation, vertisols, soil salinity, soil and water management, E. stagnina.