Decomposition of sesbania sesban and lantana camara green manures: I effect of the type of green manure and rate of application
2000
Wangari, N.(Sokoine Univerity of Agriculture, Soil Science Department, Morogoro, Tanzania) | Msumali, G.P.(Sokine University of Agrilture, Department of Agriculture, Morogoro, Tanzania)
A study was conducted to assess the effect of the green manures Sesbania sesban and Lantana camara) and the rates of their application on their decomposition under glasshouse conditions. Two rates of application (on a hectare equivalent) were tested, namely, 3.7.5 and 7.50 tonnes/ha for Sesbania or 2.75 and 5.50 tonnes/ha for Lantana. The above rates were targeted to supply the equiva¬lent of 60 and 120kg/ha in each case, assuming complete decomposition.The plant materials were loosely-packed into plastic litter bags and incorporated 10cm deep into the soil contained in wood¬en troughs. Each trough was divided into 45 x 35 x 20cm compartments each suffi¬cient to contain one litre bag. The manures were incubated at field capacity moisture content for 12 weeks. Changes in dry mat¬ter weight, organic carbon and viable (total) microbial populations were moni¬tored at three-week intervals.Using dry matter as a parameter, Sesbania decomposed significantly (P=0.05) faster than Lantana. However, this difference was not evident when residual organic C was used to assess decomposition. The quanti¬ties of manure applied did not affect the rates of decomposition over the entire incu¬bation period. Manured soil had consistent¬ly higher microbial counts than the control soil. Soil amended with Sesbania stimulat¬ed a significantly (P=0.05) higher microbial population than that amended with Lantana.The two decomposition parameters i.e. loss in dry weight and organic carbon were not consistent in describing the decomposition trend of the two types of manure. These two parameters uSed individually appear to be inadequate in describing the decom¬position pattern of the manures evaluated in this study.
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