Quantifying Short-term Effects of Soil Improving Legumes on Soil Properties and Carbon Sequestration in a Degraded Paleustult in Agbani, Enugu Southeast Nigeria

Abstract

A field trial was conducted at Enugu Southeast Nigeria (6°29'N; 7°14 54'E), during the 2014 and 2015 growing seasons to quantify short-term effects of soil improving legumes [groundnut (Arachis hypogaea), Bambara groundnut (Vigna subterranean L), Soybean (Glycine max) and Pigeon pea (Cajanus cajan)] on soil properties and carbon sequestration in a degraded Typic Paleustult. The experiment was laid out in a Randomized Complete Block Design with four legumes as treatments and six replications. Some soil quality attributes, plant shoot and root biomass, and soil carbon sequestration of the legumes were measured at 90 days after planting (DAP). Results show that soil dry bulk density (1.41-1.46 Mg m-3) and gravimetric water content (GWC) (23.16 - 26.00%) in pigeon pea and Bambara groundnut plots were lower than that in other plots by about 10-14% whereas soil saturated hydraulic conductivity (Ksat) was higher in pigeon pea and Bambara groundnut plots (23.45 - 33.10 Cm hr-1) by 14-28% for both seasons. The soil organic carbon content (SOC) (0.75 - 0.83%) and Total N (0.074 - 0.091%) in pigeon pea and Bambara groundnut plots were higher than that in soybean and groundnut plots by about 17 and  5-6% respectively for both seasons. The highest carbon sequestration was obtained in fields of Pigeon pea and Bambara groundnuts. These results depict that the legumes used improved soil quality, increased above- and below-ground biomass and improved carbon sequestration. Pigeon pea and Bambara groundnut exerted the most positive influence on soil carbon sequestration in the study area. Efficient cropping systems can be used to optimize carbon sequestration which in turn enhances soil productivity, reduces the enrichment of atmospheric CO2 and mitigates climate change in soils.