Nitrogen mineralization from cattle manure, filtermud, factory ash and nitrogen uptake by maize (zea mays) in a glasshouse experiment."

Abstract

To reduce over reliance on inorganic fertilizers due to high prices, there is a need to increase utilization of organic input sources such as filtermud, which is a by-product of white sugar manufacture. Fresh filtermud(FM) is detrimental to crops and it takes long ( > six months) to decompose under natural conditions. Supply of decomposed filtermud is limiting due to its high demand as its use is well established among farmers in the Kenyan sugar belt. Consequently, a study was conducted to improve filtermud quality through reduced curing time hence enhance nutrient release. ,The approach was: chemical characterization of filtermud, cattle manure and factory ash followed by laboratory· incubation of filtermud mixed with factory ash and or mineral nitrogen at different ratios. Nitrogen uptake by maize was assessed through a glasshouse pot experiment. The laboratory incubation experiment was held for 12 weeks with sampling at 2 weeks interval; each time mineral nitrogen (N03- and NH4+) forms were analysed. Miwani FM was strongly acidic with a pH value of 4.93 and relatively lower lignin content than that from Muhoroni and Chemelil. In terms of nitrogen release it was superior to that from Chemelil and Muhoroni, releasing 53% of nitrogen after 12 weeks. Regression analysis of nitrogen release versus material quality showed that there was a negative linear relationship between the % lignin content (r 0.99), lignin + polyphenol to nitrogen ratio (r= -0.93), lignin to nitrogen ratio (r =-0.93) carbon to nitrogen ratio (r=-0.85) on nitrogen release; hence % lignin was predominant factor controlling the nitrogen release. A maize crop was grown for 9 weeks in pots containing soils with FM from Miwani mixed with or without mineral nitrogen at the following rates; 0, 7.5, IS, 30 and 45 tha -1 •, soil mixed with 100 kq'Nha ? was included giving a total of six treatments. FM at 45 tha-1 ammended with mineral nitrogen at 9 kg N per ton of FM gave significantly (PsO. OS)) higher dry matter (19g/pot) and nitrogen uptake (13%) than the rest of the treatments. Therefore, for an inherently low fertile soil for example, cambisol 45tha-1 FM amended with mineral nitrogen at 9 kg N/ton of FM would be required to improve the fertility and hence nutrient availability. The study should be continued under field conditions for results to be conclusive.