Browsing by Author "Masha, Jamhuri Amin"

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The response of bambara groundnut (Vigna subterranean (L.) Verde) to moisture regimes in terms of growth and productivity.
(Sokoine University of Agriculture, 2001) Masha, Jamhuri Amin
Two experiments were conducted in Morogoro, Tanzania to assess the physiological effects of moisture regimes on growth, development and yield of two bambra groundnut landraces. Each experiment was conducted under screen house and field conditions during the 1998 and 1999 growing season. In the first experiment, four moisture regimes were employed by supplying irrigation water equivalent to 500、375, 250 and 125mm of rain per growing season starting from 21 days after sowing (DAS). In the second experiment, water stress was imposed by withholding water supply at vegetative stage (21 — 46 DAS), flowering stage (46 - 70 DAS) and pod filling stage (70 一 100 DAS). The experimental design was split-plot laid out in a randomized complete blocks with three replications. Two laiidraces (cream and red) constituted the main plot factors while the moisture regimes and water stress imposed at three growth stages constituted the sub plot-factors in the first and second experiments respectively. Sequential growth measurements were taken from single plant and two plants were uprooted at 46, 70, 100 and 120 DAS fbr screen house and field experiments, respectively, to measure number of leaves, flowers and pods and dry matter of leaves, stems, roots and pods. The sampled plants were pre-determined from 21 DAS to avoid bias. Plants in the inner two rows under field conditions were reserved only fbr final harvest. Decreased irrigation water and water stress imposed at vegetative stage did not significantly (P<0.05) affect the onset of flowering and maturity of the two bambara groundnut landraces. Similarly, decreased irrigation water did not affect the number of flowers upto 70 DAS. Late in tsignificantly more flowers than the well watered plants (the 500 and 375mm treatments). Water stress imposed at vegetative and flowering stages significantly reduced number of flowers per plant during the treatment periods. Leaf number, DM of leaves, stems, roots and LAI increased with increasing irrigation water from 125 to 500mm of rain equivalent. However, there were no significant differences between the 500 and 375mm; 375 and 250mm; or 250 and 125mm treatments, except at 100 DAS where the 500 and 375mm; and 375 and 250mm treatments showed significant differences fbr the above variables. Although root DM increased with increasing amount of irrigation water, the percentage of total DM partitioned to roots increased with decreasing amounts. Pod yield at final harvest also increased with increasing irrigation water. Two distinct categories were observed such that with few exceptions, most of the parameters reported above correlated well with the final yield. Pod yield did not differ significantly between the 500 and 375mm and between the 250 and 125mm treatments. Water stress at any of the three growth stages reduced number of leaves, DM of leaves, roots, stems, and LAI. However a significant difference in these variables was observed fbr water stress imposed at vegetative and flowering stages. After relieving water stress, re-growth was observed such that at final harvest there were no significant differences among the stressed plants, except fbr root DM. Pod yield was significantly reduced by water stress particularly at flowering. At this growth stage water stress is the most detrimental to bambara groundnut yield, followed by water stress at pod filling stage. There was no significant difference in shelling percentage across treatments. Pod yield was positively con-elated with leaf number, leaf, stem and root dry matter and pod number; buthe negatively correlated with flower number. It was concluded that, onset of flowering is not affected by rainfall equivalent as low as 125mm if well distributed. However, rainfall or irrigation equivalent of less than 375mm per growing season is not recommended for optimum bambara groundnut production. On the other hand, under water stress conditions, bambara groundnut tends to partition more DM to roots than above ground parts, a mechanism considered to be associated with drought tolerance of the crop. Flowering stage was the most water sensitive with respect to growth and yield. season, the most water stressed plants (the 250 and 125mm treatments) produced