Monitoring and Modeling of Saline-Sodic Vertisol Reclamation by Echinochloa stagnina

Maman Nassirou Ado,Zahra Thomas,Christian Walter,Yadji Guero,Didier Michot

doi:10.3390/soilsystems6010004

Abstract

Soil salinity due to irrigation is a major constraint to agriculture, particularly in arid and semi-arid zones, due to water scarcity and high evaporation rates. Reducing salinity is a fundamental objective for protecting the soil and supporting agricultural production. The present study aimed to empirically measure and simulate with a model, the reduction in soil salinity in a Vertisol by the cultivation and irrigation of Echinochloa stagnina. Laboratory soil column experiments were conducted to test three treatments: (i) ponded bare soil without crops, (ii) ponded soil cultivated with E. stagnina in two successive cropping seasons and (iii) ponded soil permanently cultivated with E. stagnina with a staggered harvest. After 11 months of E. stagnina growth, the electrical conductivity of soil saturated paste (ECe) decreased by 79–88% in the topsoil layer (0–8 cm) in both soils cultivated with E. stagnina and in bare soil. In contrast, in the deepest soil layer (18–25 cm), the ECe decreased more in soil cultivated with E. stagnina (41–83%) than in bare soil (32–58%). Salt stocks, which were initially similar in the columns, decreased more in soil cultivated with E. stagnina (65–87%) than in bare soil (34–45%). The simulation model Hydrus-1D was used to predict the general trends in soil salinity and compare them to measurements. Both the measurements and model predictions highlighted the contrast between the two cropping seasons: soil salinity decreased slowly during the first cropping season and rapidly during the second cropping season following the intercropping season. Our results also suggested that planting E. stagnina was a promising option for controlling the salinity of saline-sodic Vertisols.

Highlights

Irrigated land degradation by salinization is a major constraint for agricultural production on irrigated soils, in arid and semi-arid zones
The changes in the soil pressure head on all the columns showed a saturated soil with a decreasing moisture gradient from the topsoil to the deepest soil layer during the cropping seasons (S1 and S2) and a desaturated soil with highly marked soil drying during the intercropping season (IC) (Figure 2)
In deepest soil layer (18–25 cm), the electrical conductivity of soil saturated paste (ECe) decreased less in bare soil (32–58%) than in soil cultivated with E. stagnina (72–83%), except in replicate CEp2, for which the ECe decreased by only 41%

Summary

Introduction

Irrigated land degradation by salinization is a major constraint for agricultural production on irrigated soils, in arid and semi-arid zones. It has been estimated that 33% of irrigated agricultural land worldwide is afflicted by high salinity for various reasons, including low precipitation, high surface evaporation, weathering of native rocks, irrigation with saline water, and unsuitable cultural practices [2] Clayey soils, such as vertic soils in the Niger River valley, which are irrigated for rice production in Niger, are exposed to salinization because of their low hydraulic conductivity at water saturation which inhibits salt leaching [3,4]. This approach is increasingly investigated, both in field studies [12,13,14,15] and under controlled laboratory conditions [10,16,17,18] since water ponding is difficult to apply in water-limited areas and less effective in fine-textured soils [4,19,20]

Objectives

Methods

Results

Conclusion