Effect of biomass management regimes and wetting-drying cycles on soil carbon mineralization in a Sudano-Sahelian region

In Sudano-Sahelian regions, wetting-drying cycles may affect soil carbon mineralization in soil already poor in carbon. Conservation agriculture systems by improving crop residues return to soil is given to increase soil organic carbon and soil fertility. We studied the effect of biomass management regimes and wetting-drying cycles on soil carbon stocks and mineralization. A 50-day experiment was set up to compare carbon mineralization under two biomass management regimes, with and without mulch, using three soil wetting treatments. Wetting the soil and mulching increased soil carbon mineralization. However, wetting-drying cycles did not increase the soil carbon mineralization as compared with soils kept moist. During the experiment, the total carbon mineralization from the dry soils was low, 0.63 tC ha(-1) and 0.53 tC ha-I respectively for soils with and without mulch. Total carbon mineralization from soil without mulch was 1.40 tC ha(-1) with wetting-drying cycles and 1.51 tC ha(-1) for soils that were kept moist. Total carbon mineralization from soils with mulch was 1.70 tC ha(-1), regardless of whether the soils had wetting-drying cycles or were kept moist. In our context, characterized by very little crop residues and rapid mineralization of this biomass, the conservation agriculture systems do not seem sufficient to increase soil organic carbon stocks

Evaluation of cover crop contributions to conservation agriculture in northern Benin

Context or problem: Conservation agriculture is a sustainable farming system designed to enhance agroecosystem productivity, adaptability, and the conservation of natural resources and biodiversity, while reducing production costs. In the context of northern Benin, understanding the role of cover crops in biomass production and soil improvement is crucial for promoting and adopting conservation agriculture practices. Objective or research question: This study aimed to contribute valuable insights into the growth performance and impact of 10 cover crop species in the Okpara and five in Angaradebou regions of northern Benin. Methods: The study employed a split-block design to assess cover crop growth during the rainy season of 2018. Plant density, height, aboveground biomass, and grain productivity were measured. In the subsequent season, the experimental setup was transformed into a strip-split plot design to evaluate how soil cover management, specifically mulched cover (M) or standing cover (L), influenced soil ground cover, water infiltration, soil moisture, and weed density. Results: The findings of the study indicated that Sesbania rostrata and Mucuna pruriens produced the tallest plants in the Okpara region, while Crotalaria juncea, Brachiaria ruziziensis, and Crotalaria retusa were the tallest in the Angaradebou region. Brachiaria ruziziensis, Crotalaria juncea, Crotalaria ochroleuca, and Sesbania rostrata exhibited the highest biomass production. In terms of yield components, Crotalaria ochroleuca and Crotalaria juncea performed well in seed production per pod, while Mucuna pruriens and Cajanus cajan had the highest seed weight. Regarding ground cover, Brachiaria ruziziensis demonstrated the highest performance, with 60% and 89% ground cover as mulch and standing cover, respectively, followed by Stylosanthes guianensis. Plots with better ground cover exhibited higher soil moisture retention (7–13%) and hydraulic conductivity (0.0015 cm² s−1 - 0.002 cm² s−1), as well as lower weed densities (55–69 weeds m−2). Stylosanthes guianensis and Sesbania rostrata showed the best soil moisture retention (11% and 13%, respectively), followed by Crotalaria juncea, Mucuna pruriens, and Brachiaria ruzisiensis (13%). Conclusions: The study highlighted the agronomic performance of 10 cover crops under conservation agriculture and their potential to positively impact soil physical properties and weed dynamics in northern Benin. Implications or significance: These cover crops have the potential to diversify cotton-based cropping systems in the region, thereby enhancing their sustainability. However, further investigation is needed to explore the effects of these cover crop species on intercrop combinations and crop and cover crop sequences under the specific agroecological conditions of northern Benin.</p