Managing N availability and losses by combining fertilizer-N with different quality residues in Kenya

• Published in: Agriculture, ecosystems & environment Vol. 131; no. 3; pp. 308 - 314
• Main Authors: Gentile, R., Vanlauwe, B., van Kessel, C., Six, J.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 01.06.2009; Amsterdam; New York: Elsevier; Elsevier
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; carbon nitrogen ratio; corn; crop residues; environmental factors; fertilizer rates; forage crops; forage legumes; Fundamental and applied biological sciences. Psychology; General agroecology; General agroecology. Agricultural and farming systems. Agricultural development. Rural area planning. Landscaping; General agronomy. Plant production; Generalities. Agricultural and farming systems. Agricultural development; Kenya; Leaching; Maize; Mineralization; N fertilizers; nitrification; nitrogen; nitrogen content; nitrogen fertilizers; Nitrogen, phosphorus, potassium fertilizations; nutrient availability; nutrient management; Residue quality; soil fertility; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Tithonia; Tithonia diversifolia; Zea mays; Kenya; East Africa; Sub-Saharan Africa; Africa; N fertilizers; Maize; Residue quality; Mineralization; Leaching; Monocotyledones; Zea mays; Tropical zone; Available nutrient; Ecology; Nitrogen; Cereal crop; Gramineae; Residue; Quality; Angiospermae; Spermatophyta; Chemical composition; Nitrogen fertilizer
• ISSN: 0167-8809; 1873-2305
• DOI: 10.1016/j.agee.2009.02.003

The integrated soil fertility management paradigm, currently advocated in Sub-Saharan Africa for rehabilitating its soils, recognizes the possible interactive benefits of combining organic residues with mineral fertilizer inputs on agroecosystem functioning. Residue quality may be a controlling factor for any beneficial interactions. The objectives of this study were to determine the effect of different quality organic residues and mineral fertilizer on N cycling under field conditions in Embu, Kenya. We hypothesized that combining low quality residue with mineral N would reduce potential system losses of N by synchronizing N release with plant uptake. Residue treatments consisted of a control (no residue input), high quality tithonia ( Tithonia diversifolia) residue (C to N ratio of 13:1) and low quality maize ( Zea mays) stover residue (C to N ratio of 42:1) applied at a rate of 1.2 Mg C ha −1. Subplots of each residue treatment received either 0 or 120 kg N ha −1 in a split-application, and maize was cultivated each season. During the 11th growing season of the trial (March–September 2007), we monitored soil mineral N, potential gross mineralization and nitrification rates, and plant N content. Extractable mineral N in the soil profile varied with residue and fertilizer inputs throughout the growing season. The tithonia treatments showed early season N release of 22 kg N ha −1 in the upper 30 cm of the soil profile. The maize + fertilizer treatment displayed an immobilization of 34 kg N ha −1 after the application of N fertilizer. However, the lower mineral N of the maize + fertilizer treatment did not reduce crop N uptake, as mineral N in the other fertilizer treatments was leached from the upper soil (0–60 cm) at 57 d after planting. The interactive effect on crop yield and N uptake of combining residue with fertilizer-N changed from negative to positive as residue quality decreased. The benefit of combining low quality residue with N fertilizer in reducing N losses indicates that this soil fertility management strategy should be adopted in environments subject to high N leaching losses.