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Aluminum toxicity is a major limitation to crop production on highly weathered and leached soils in Rwanda. Moreover, sulfur though widely deficient in Rwanda acidic soils has received little attention by soil fertility researchers. A field experiment on maize response and soil nutrients status to liming materials of travertines at 3.4 t ha−1, ash wood 1.2 t ha−1of CaO equivalent and sulfur at 10 kg ha−1combined with NPK at 80, 60, and 45 kg ha−1respectively was conducted in Rubona Ultisol and Nyamifumba Oxisol. Results revealed that travertine and wood ash increased the soil pH from 4.7 to 5.8 or higher and decreased exchangeable Al3+and H+to near 0 cmolc kg−1. Soil nutrients generally increased to high or medium ranges for crop production. Leaf dry biomass, plant height and maize grain yields were significantly higher in Rubona Ultisol than in Nyamifumba Oxisol. Plots that received wood ash, with NPKS or with NPK, generally had higher maize yields, followed by those which received travertines and NPKS or NPK which had maize growth response as compared to the control plots which received NPK only. Thereby, a combination of wood ash with NPKS or NPK, travertines with NPKS was found to neutralize soil aluminum toxicity, increase soil nutrients status to required levels for plant growth and increase maize yields significantly. [ABSTRACT FROM PUBLISHER]

A field experiment investigating amendments of organic material including farmyard manure, paper factory sludge and crop residues combined with fly ash, lime and chemical fertilizer in a rice-peanut cropping system was conducted during 1997-98 and 1998-99 at the Indian Institute of Technology, Kharagpur, India. The soil was an acid lateritic (Halustaf) sandy loam. For rice, an N:P:K level of 90:26.2:33.3 kg ha-1 was supplied through the organic materials and chemical fertilizer to all the treatments except control and fly ash alone. The required quantities of organic materials were added to supply 30 kg N ha-1 and the balance amount of N, P and K was supplied through chemical fertilizer. Amendment materials as per fertilization treatments were incorporated to individual plots 15 days before planting of rice during the rainy season. The residual effects were studied on the following peanut crop with application of N:P:K at 30:26.2:33.3 kg ha-1 through chemical fertilizer alone in all treatments, apart from the control. An application of fly ash at 10 t ha-1 in combination with chemical fertilizer and organic materials increased the grain yield of rice by 11% compared to chemical fertilizer alone. The residual effect of both lime and fly ash applications combined with direct application of chemical fertilizer increased peanut yields by 30% and 24%, respectively, compared to chemical fertilizer alone. Treatments with fly ash or lime increased P and K uptake in both the crops and oil content in peanut kernel compared to those without the amendments. Alkaline coal fly ash proved to be a better amendment than lime for improving productivity of an acid lateritic soil and enriching the soil with P and K. [ABSTRACT FROM AUTHOR]