Critical soil organic carbon range for optimal crop response to mineral fertiliser nitrogen on a ferralsol
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Date
2016
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Experimental Agriculture
Abstract
Soil Organic Carbon (SOC) is a major indicator of soil fertility in the tropics and underlies variability in crop response to mineral fertilizers. Critical SOC concentrations that interact positively with N fertilizer for optimal crop yield are less understood. A study was conducted on a Ferralsol in sub-humid Uganda to explore the critical range of SOC concentrations and associated fractions for optimal maize (Zea mays L.) yield response to applied mineral N fertiliser. Maize grain yield response to N rates applied at 0, 25, 50 and 100 kg N ha−1 in 30 fields of low fertility (SOC < 1.2%), medium fertility (SOC = 1.2–1.7%) and high fertility (SOC > 1.7%) was assessed. Soil was physically fractionated into sand-sized (63–2000 µm), silt-sized (2–63 µm) and clay-sized (<2 µm) particles and SOC content determined. Low fertility fields (<1.2% SOC) resulted in the lowest response to N application. Fields with >1.2% SOC registered the highest agronomic efficiency (AE) and grain yield. Non-linear regression models predicted critical SOC for optimal yields to be 2.204% at the 50 kg N ha−1 rate. Overall, models predicted 1.9–2.2% SOC as the critical concentration range for high yields. The critical range of SOC concentrations corresponded to 3.5–5.0 g kg−1 sand-sized C and 9–11 g kg−1 for clay-sized C.
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Patrick Musinguzi, P. Musinguzi, John Stephen Tenywa, J. Stephen Tenywa, Peter Ebanyat, P. Ebanyat, Twaha Ali Basamba, T. Ali Basamba, Moses Makooma Tenywa, M. Makooma Tenywa, Drake N. Mubiru, D. N. Mubiru, & Yuri L. Zinn, Y. L. Zinn. (2015). Soil organic fractions in cultivated and uncultivated Ferralsols in Uganda. Geoderma regional, 4, 108-113. doi: 10.1016/j.geodrs.2015.01.003