Theses and Dissertations Collection

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Browsing Theses and Dissertations Collection by Subject "Agronomic practices"

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    Evaluation of agronomic practices for optimising biological nitrogen fixation and yields of Bambara groundnut [Vigna Subterranea (L.) Verde.]
    (Sokoine University of Agriculture, 2009) Mkwachu, Seif Omari
    Studies were conducted to evaluate agronomic practices for optimizing biological nitrogen fixation of bambara groundnut [Vigna subterranea (L.) Verde.]. An experiment was conducted during 2005/6 at Sokoine University of Agriculture (SUA) to screen ten bambara groundnuts landraces for their ability to withstand effect of nutrients and moisture stress in N2 fixation. During the 2005/6 cropping season, field experiments were also conducted at Msisi and Hombolo villages in Dodoma to study the effects of three selected landraces and three crop densities of bambara groundnut on yields and nitrogen fixation. Treatments were arranged in a split plot in a Randomised Complete Block Design (RCBD) with six replications using the mother and baby system approach. Bambara groundnut landraces were the main treatments while intra row spacing was the sub plot treatment. During the 2006/07 cropping season the experiment was repeated on the same plots to assess the residue N benefit to subsequent cereals against weed fallow and continuous cereal cropping. Results showed significant differences (P<0.05) between landraces in most of the variables tested. Under moisture stress conditions, Red landrace fixed significantly (P<0.05) highest levels of N2 (0.27gplanf’) while Nkonya, the least efficient, fixed only O.Mgplant'1. Under moisture stress growth variables with strong influence on the amount of N2 fixed were leaf area (r= 0.400, P<0.01), number of nodule (r - 0.470, P<0.01) and plant weight (r = 0.286, P<0.05 ). A plant density of 16 plants m"2 (20 cm by 30 cm) with mean seed yield of 4.07gplant (625.6kg/ha), residue dry matter yield of 12.16g/plant (2tha**) and mean fixed N2 of 25.77kg/ha was optimal for yield and N2 fixation. Drought tolerance and ability of bambara groundnut to form effective nodule with native rhizobia are major physiological basis of sustaining N2 fixation under moisture stress. The fertilizer N equivalent value contributed by bambara groundnut suggests that sorghum is a more suitable crop to Follow bambara groundnut in rotation as compared to maize. However, analysis of marginal rate of returns showed that continuous bambara groundnut is economically profitable. Hence, under marginal conditions, growing landrace Cream at spacing of 20 cm by 30 cm continuously was recommended under moisture stress. The fertilizer N equivalent value contributed by bambara groundnut suggests that sorghum is a more suitable crop to follow bambara groundnut in rotation as compared to maize. However, analysis of marginal rate of returns showed that continuous bambara groundnut is economically profitable. Hence, under marginal conditions, growing landrace Cream at spacing of 20 cm by 30 cm continuously was recommended.