Decomposition, nitrogen and phosphorus mineralization from winter-grown cover crop residues and suitability for a smallholder farming system in South Africa

• Published in: Nutrient cycling in agroecosystems 2011-01, Vol.89 (1), p.115-123
• Main Authors: Murungu, F. S, Chiduza, C, Muchaonyerwa, P, Mnkeni, P. N. S
• Format: Article
• Language: English
• Subjects: Agricultural conservation; Agricultural practices; Agriculture; Avena sativa; biodegradation; biogeochemical cycles; Biomedical and Life Sciences; Corn; Cover crops; Crop residues; Cropping systems; Crops; Decomposition; Environmental degradation; Farming systems; Forage; forage legumes; Grazing; Irrigation systems; Land degradation; Land use; Legumes; Life Sciences; Mineralization; Nitrogen; nutrient availability; Nutrient release; nutrient uptake; Nutrients; Oats; Organic matter; Organic soils; Original Article; Peas; Phosphorus; Pisum sativum; Residues; Small farms; small-scale farming; Soil; Soil conservation; soil degradation; Soil improvement; Soil organic matter; Stover; Summer; temporal variation; vegetation cover; Vicia; Vicia villosa subsp. varia; Winter; Zea mays
• ISSN: 1385-1314; 1573-0867
• DOI: 10.1007/s10705-010-9381-5

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.