Abstract
Decline in Soil Organic Carbon (SOC) below the critical levels is one of the major indicators of soil fertility depletion in Sub-Saharan Africa (SSA), with the main causes being poor management practices coupled with low input use. Measures for monitoring long-term impacts of management on SOC dynamics and its restoration can be critical in enhancing sustainable soil productivity. Crop models have proved to be good tools for understanding the influence of management options on soil and crop productivity. The DSSAT-Century model was applied to simulate the influence of management practices on SOC dynamics. Using long-term datasets from Kabete, Kenya (1976-1996 maize-bean) and Kiboga-Uganda (1980-2010 maize), model calibration and evaluation showed a good fit between simulated and observed values of SOC. On simulating continuous tillage with no fertilization for the 1980-2010 antecedent period and 2010-2060 extrapolated period, the model showed high rates of SOC decline in the newly cultivated soil as compared to a degraded soil. The simulated rate of decline is 2129 kg ha -1 yr -1 for newly cultivated soil and 849 kg ha -1 yr -1 for the continuously cultivated soils. The model was sensitive to initial partitioning of SOC pools, with SOC in previously uncultivated soils declining at a higher rate than that in the cultivated ones. The model confirmed that use of continuous tillage is a major threat to SOC building and soil fertility restoration in the tropics. Adopting conservation agriculture is critical for future generations. Overall, the DSSAT CENTURY model is a potential tool for predicting SOC dynamics in low-input farming systems.
Highlights
Soil Organic Carbon (SOC) is a key soil fertility indicator in heterogeneous tropical farming systems in Sub-Saharan Africa (Woomer, Martin, Albretch, Resck, & Scharpenseel, 1994; Musinguzi et al, 2013)
Decline in Soil Organic Carbon (SOC) below the critical levels is one of the major indicators of soil fertility depletion in Sub-Saharan Africa (SSA), with the main causes being poor management practices coupled with low input use
With Longe 5 variety, an open pollinated variety, the simulated yield ranges fall within the average observed yields that have been reported in Uganda
Summary
Soil Organic Carbon (SOC) is a key soil fertility indicator in heterogeneous tropical farming systems in Sub-Saharan Africa (Woomer, Martin, Albretch, Resck, & Scharpenseel, 1994; Musinguzi et al, 2013). SOC varies with soil fertility heterogeneity, resulting in high yield variability, and uncertainty in nutrient management. Low fertility soils are associated with low SOC due to poor soil management practices and rapid decomposition (van Keulen, 2001). Restoring SOC to acceptable levels is, a necessary component of soil fertility improvement and increased crop productivity. In order to understand the processes and practices that affect SOC in terms of its depletion, maintenance and restoration, models that simulate soil and crop performance cannot be underestimated. The model simulates SOM decomposition processes as a potential major source of nutrients for some low input farming systems. When the model was compared with a set of other eight soil organic matter models using 12 long-term data sets (Smith et al, 1997), the CENTURY model (Parton, Ojima, Cole, & Schimel, 1994), was among the best. Porter et al (2010) described major changes to the model by improving initialisation routines to allow flexibility in user input, improving functions for the response of organic matter to changes in soil, water and www.ccsenet.org/jas
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