Maize productivity and nutrient dynamics in maize-fallow rotations in western Kenya

• Published in: Plant and soil 2004-07, Vol.264 (1-2), p.195-208
• Main Authors: Bunemann, E.K, Smithson, P.C, Jama, B, Frossard, E, Oberson, A
• Format: Article
• Language: English
• Subjects: Acid soils; Agricultural practices; Agricultural seasons; Agricultural soils; Agrochemicals; Agronomy. Soil science and plant productions; Biological and medical sciences; Biomass; Cereal crops; continuous cropping; Corn; Crop rotation; Crop yield; Cropping systems. Cultivation. Soil tillage; Crotalaria; Crotalaria grahamiana; Experiments; fallow; Fallow land; Fallowing; Fertilization; fertilizer application; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Generalities. Cropping systems and patterns; grain crops; intercropping; Mineral fertilizers; nitrogen; Nitrogen fixation; Nutrient dynamics; Organic soils; Pests; phosphorus; phosphorus fertilizers; plant nutrition; Plant production; Rainy season; Seasons; Soil; Soil microorganisms; soil nutrients; Soil properties; soil-plant interactions; Soil-plant relationships. Soil fertility; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Sustainability; triple superphosphate; Tropical soils; Zea mays
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1023/B:PLSO.0000047749.43017.fd

One-season fallows with legumes such as Crotalaria grahamiana Wight & Arn. and phosphorus (P) fertilization have been suggested to improve crop yields in sub-Saharan Africa. Assessing the sustainability of these measures requires a sound understanding of soil processes, especially transformations of P which is often the main limiting nutrient. We compared plant production, nitrogen (N) and P balances and selected soil properties during 5.5 years in a field experiment with three crop rotations (continuous maize, maize-crotalaria and maize-natural fallow rotation) at two levels of P fertilization (0 and 50 kg P ha⁻¹ yr⁻¹, applied as triple superphosphate) on a Kandiudalfic Eutrudox in western Kenya. The maize yield forgone during growth of the crotalaria fallow was compensated by higher post-fallow yields, but the cumulative total maize yield was not significantly different from continuous maize. In all crop rotations, P fertilization doubled total maize yields, increased N removal by maize and remained without effect on amounts of recycled biomass. Crotalaria growth decreased in the course of the experiment due to pest problems. The highest levels of soil organic and microbial C, N and P were found in the maize-crotalaria fallow rotation. The increase in organic P was not accompanied by a change in resin-extractable P, while H₂SO₄-extractable inorganic P was depleted by up to 38 kg P ha⁻¹ (1% of total P) in the 0-50 cm layer. Microbial P increased substantially when soil was supplied with C and N in a laboratory experiment, confirming field observations that the microbial biomass is limited by C and N rather than P availability. Maize-legume fallow rotations result in a shift towards organic and microbial nutrients and have to be complemented by balanced additions of inorganic fertilizers.