Nitrogen availability determines the long-term impact of land use change on soil carbon stocks in grasslands of southern Ghana

• Published in: Soil 2020-11, Vol.6 (2), p.523-539
• Main Authors: Nyameasem, John Kormla, Reinsch, Thorsten, Taube, Friedhelm, Domozoro, Charles Yaw Fosu, Marfo-Ahenkora, Esther, Emadodin, Iraj, Malisch, Carsten Stefan
• Format: Article
• Language: English
• Subjects: Agricultural land; Agricultural management; Arable land; Availability; Biodegradation; Carbon; Cattle; Climate change; Climate change mitigation; Conversion; Crop fields; Emissions; Farms; Fertility; Forage species; Functional groups; Grasslands; Land use; Legumes; Livestock; Loam soils; Manures; Metabolites; Nitrogen; Organic carbon; Organic soils; Pasture; Savannahs; Shrubs; Soil; Soil degradation; Soil fertility; Soil improvement; Soil management; Soils; Stocks; Storage; Sustainable use; Systems analysis; Tannins; Tropical climate
• ISSN: 2199-398X; 2199-3971; 2199-398X; 2199-3971
• DOI: 10.5194/soil-6-523-2020

Enhancing the capacity of agricultural soils to resist soil degradation and to mitigate climate change requires long-term assessments of land use systems. Such long-term evaluations, particularly regarding low-input livestock systems, are limited. In the absence of suitable long-term experiments, this study assessed the outcome of C inputs and outputs across an array of plant functional groups in arable and permanent systems of a tropical savannah after more than 50 years of consistent land use. Soil samples were taken (0–30 cm depth) from arable crop fields, grazed–seeded grassland, cut–use permanent crops and native grassland. Soil organic carbon (SOC) stocks ranged from 17 to 64 Mg SOC ha−1 (mean ± sd = 32.9 ± 10.2 Mg ha−1). SOC stocks were lower for grazed–seeded grassland relative to cut–use grass, legume trees and shrubs. Accordingly, while the conversion of the native grassland to grazed pastures caused an estimated loss of 44 % of SOC over the period, the conversion to woody legumes resulted in slight (5 %), incremental gains. Within sown systems, nitrogen (N) availability seemed to be the most critical factor in determining the fate of the SOC stocks, with the soil N concentration and SOC being highly correlated (r – 0.86; p