Decomposition,nitrogen and phosphorus mineralization from winter-grown cover crop residues and suitability for a smallholder farming system in South Africa |
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Authors: | F S Murungu C Chiduza P Muchaonyerwa P N S Mnkeni |
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Affiliation: | (1) Department of Agronomy, Faculty of Science and Agriculture, University of Fort Hare, P. Bag X1314, Alice, 5700, South Africa; |
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Abstract: | Increasing land degradation has prompted interest in conservation agriculture which includes growing cover crops. Besides
providing soil cover, decaying cover crops may release substantial amounts of nutrients. Decomposition, N and P release from
winter cover crops grazing vetch (Vicia darsycarpa), forage peas (Pisum sativum) and oats (Avena sativa)] were assessed for suitability in a cropping system found in the smallholder irrigation sector of South Africa. Nitrogen
and P contribution to maize growth by cover crop residues was also estimated. Decrease in mass of cover crop residues was
highest in grazing vetch (7% remaining mass after 124 days) followed by forage peas (16%) and lastly oats (40%). Maximum net
mineralized N and P were higher for grazing vetch (84.8 mg N/kg; 3.6 mg P/kg) than for forage peas (66.3 mg N/kg; 2.7 mg P/ha)
and oats (13.7 mg N/kg; 2.8 mg P/kg). Grazing vetch and forage pea residues resulted in higher N contribution to maize stover
than oat residues. Farmers may use grazing vetch for improvement of soil mineral N while oats may result in enhancement of
soil organic matter and reduction land degradation because of their slow decomposition. Terminating legume cover crops a month
before planting summer crops synchronizes nutrient release from winter-grown legume cover crops and uptake by summer crops. |
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