Nitrogen mineralization from cattle manure, filter¬mud, factory ash and nitrogen uptake by maize (zea mays) in a glasshouse experiment
2000
Amolo, R.A.(University of Nairobi, Department of Soil Science, Nairobi, Kenya) | Karanja, N.K.(University of Nairobi, Department of Soil Science, Nairobi, Kenya) | Palm, C.A.(Tropical soil Biologv and Fertility, UNESCO ROSTA, Nairobi)
A study was conducted to improve nitro¬gen release ability from filtermud(FM) through reduced curing time. Chemical analysis of filtermud, cattle manure, factory ash and soil samples were carried out.Laboratory incubation experiments using filtermud alone or in mixtures at var¬ious ratios with factory ash and mineral nitrogen was conducted for a period of 12 weeks. Cattle manure and factory ash (alone or in combination with mineral nitrogen) were included to make 15 treat¬ments. Miwani FM was found to be strongly acidic (pH 4;~3) and relatively with less lignin conteht cqropared to that from Muhoroni and Chemelil. In terms of nitrogen release Miwani FM was superior to that from Chemelil and Muhoroni, as it released 53% of nitrogen (available) after 12 weeks. Regression analysis of nitrogen release showed that there was a negative linear relationship ~ith the following; % lignin content (r = -0.99),lignin to nitrogen ratio (r = -0.93) and carbon to nitrogen ratio (r=¬0.85), hence lignin was the predominant factor controlling the nitrogen release from these organic materials. A maize crop was grown for 9 weeks in pots containing soils with FM from Miwani mixed with or with¬out mineral nitrogen at the following rates; 0, 7.5, 15,30 and 45 tha-I, soil mixed with 100 kg N ha-I was included giving a total of six treatments. FM at 45 tha-I amended with mineral nitrogen at the rate of 9 kg N per ton of FM gave significantly (P::O;O.05)) higher dry matter (19g/pot) and nitrogen uptake (13%) than the rest of the treatments. Therefore, for an inherently low fertile soil such as Cambisol addition of 45tha-l FM amended with mineral nitrogen at 9 kg N (calcium ammonium nitrate) per ton ofFM would be required to improve the fertility and hence nutrient availability. Field trials need to be conducted, since the results' were laboratory based.
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