Abstract
The effects of cow dung and wood ash applications with and without rhizobial inoculation on modulation, and N2-fixation by soybean (Glycine max (L.) Merrill) were investigated in tropical acid dystrudepts under greenhouse and field conditions. The field experiments were located at Epe and Ijebu-waterside (Ibiade) of Lagos and Ogun States, southwestern Nigeria, respectively. The experiment was a 3 x 3 x 2 factorial experiment, arranged in a randomized complete block design (RCBD) with three replications. The treatments were three rates (0, 5, and 10 t ha-1) of cow dung, three rates (0, 2.5 and 5.0 t ha-1) of wood ash and two levels of inoculation (inoculated and un-inoculated). Inoculation significantly (p < 0.05) increased the number of nodules and the N-fixed by soybean. The increase in the numbers of nodules of the inoculated over the un-inoculated soybean under field conditions at Epe and Ijebu-waterside were 76% and 98% respectively. The amount of nitrogen fixed was found to be greatest at 5 t ha-1 of both cow dung and wood ash in the greenhouse. The soil pH increased with the increasing rate of cow dung and wood ash applications at the two locations. The maximum value of pH (7.08) was obtained at the application rate of 5 t ha-1 wood ash singly or combined with 10 t ha-1 cow dung. In the greenhouse, the grain yield increases of the un-inoculated and the inoculated soybean over the control were 39 and 86% in the soil of Epe, and 67 and 112% in the soil of Ijebu-waterside, respectively. It is concluded that a combination of cow dung and wood ash applications with rhizobial inoculation improved nodulation and N2-fixation by soybean in acid soils.
Keywords:
cow dung
n -fixed
rhiozobial-inoculation
soybean
wood ash.
2
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