Arid Agroecosystem Shrubs Enhance Enzyme Activities during the Dry Season

Abstract

In Senegal, in the Sahel region, the agroecosystem is dominated by two Sahelian shrubs able to redistribute water from deep soil to the surface. This study was carried out to determine the impact of these shrubs on soil microbial activity. A 2 × 3 factorial design was set up during the dry and wet season with three soil treatments: rhizospheric, bulk and non-rhizospheric soil. During the dry season, the presence of shrubs resulted in significantly higher phosphatase acid activity for Guiera senegalensis ( p < 0.001), respectively, 717 μg pNP/h/g of dry soil in the rhizosphere soil, 333 μg pNP/h/g in the bulk soil and 193 μg pNP/h/g in the non-rhizosphere soil. The same trend was observed for all other enzyme activities and MBC during both seasons except for mineral N. Mineral N was not statistically different between the rhizospheric and bulk soil during the dry season. β -glucosidase and phosphatase acid had the highest correlation with the rhizospheric soil during the dry season respectively 98% and 97%. Soil moisture content was highly correlated with the rhizospheric soil (85%), chitinase activity (99%) and β -glucosidase (97%). Shrubs maintained a moister environment during the dry season which was critical in stimulating microbial activities; this has significant implications for agroecosystem management in the Sahel.