Browsing by Author "Nyaki, A. S."
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Item Contribution of legume rotations to the nitrogen requirements of a subsequent maize crop on a rhodic ferralsol in Tanga, Tanzania(2013) Marandu, A. E. T.; Semu, E.; Mrema, J. P.; Nyaki, A. S.Industrial fertilizers are expensive for small-scale farmers who, as alternative, rely on legume crops for providing N for a subsequent maize crop. A legume-maize rotational experiment was carried out on a Rhodic Ferralsol at Mlingano Agricultural Research Institute in Muheza, Tanga, Tanzania, to evaluate the effects of legumes rotation in meeting the N fertilizer requirements of maize. The experimental site was located at 39o 52’E, 5o 10’S and 183 metres above sea level (m.a.s.l.). The experiment was conducted for two rotation cycles whereby cowpea, pigeonpea or greengram were grown during the short rains followed by maize during the long rains. The maize rotations were imposed on plots on which legumes had been grown during the previous legume rotation. Monoculture maize was grown with treatments of 0, 25, 50 and 100 kg N ha-1 imposed for purposes of plotting N fertilizer response curves. Based on the response curve lines, the effects of the legume rotation on maize yields were compared and translated as N fertilizer equivalency of the legumes in question. The grain and residue yields of the three legumes were significantly different (P<0.01), a fact which was attributed to the genetic differences of the legume species. The maize yields following rotation with each of the three legumes were significantly higher (P<0.05) than those under continuous maize. The effects of the rotations on increasing the maize yields were equivalent to application of 25, 19 and 16 kg N ha-1 for the cowpea, pigeonpea and greengram rotations, respectively. It was, however, concluded that the contributions of N by the legumes in the legume-maize rotations were not enough to satisfy the maize N requirements of 50 kg N/ha; hence supplementation with mineral N, in addition to the rotations, is necessary for increased yields.Item Potential of cowpea, pigeonpea and greengram to supply mineral N to maize in rotation on ferralsols in Muheza Tanga- Tanzania(2008-06) Marandu, A.E.T.; Mrema, J.P.; Nyaki, A. S.; Semu, E.A rotational field experiment of cowpea, pigeonpea and greengram with maize as married out for two rotational cycles to determine the potential of the legumes to supply N to the subsequent maize. The experiment was carried out on sandy clay Rhodic Ferralsol with bimodal rainfall pattern. The legumes were planted during the short rain season followed by maize during long rains. Soil was sampled from 0 - 20 em layer before maize planting from plots where the legumes were grown and from continuous maize plots. The composite soil samples were sieved through 6 mm screen while fresh. Sub samples equivalent to 250 g each were incubated in 500 ml wide mouth volumetric flasks at 60% field capacity and room temperature for 42 days. Destructive samplings were done at 14 days intervals and analysed for mineral N (NH4+ and N03-). The quantities of mineral N increased with incubation time. Most of the mineral N was mineralised between 0 and 14 days of incubation. Out of the total N mineralized during the entire incubation period, the proportions of the mineral N determined at the 14th day sampling were 64% for the cowpea, 50% for the pigeonpea, 73% for the greengram and 88% for the continuous maize plots. Such high proportions indicate that the subsequent maize would obtain maximum N during these early stages of growth. It was concluded that there is lack of synchrony between the release of mineral N and the maize crops' N demand which lead to the maize N deficiency symptoms and low yields observed in the legume - maize_cropping system.Item Quantification of atmospheric n2 fixed by cowpea, pigeonpea and greengram grown on ferralsols in Muheza District, Tanzania(2010) Marandu, A. E. T.; Semu, E.; Mrema, J. P.; Nyaki, A. S.Legume crops are usually intercropped with cereals in small-scale farming systems in Tanzania. This aims at taking advantage of legumes to replenish soil nitrogen (N due to legumes’ N2 fixation). Glasshouse pot experiments and field trials were carried out atMlingano Agricultural Research Institute in Tanga, Tanzania, with the objective to find out how much N2 can be fixed by cowpea, pigeonpea and greengram using native Rhizobia, thus substituting for the use of N-mineral fertilizers in maize production on Ferralsols. In the glasshouse pot experiment, the legumes were grown in 5L plastic pots for 40 days in soil sampled from 0 – 20 cm layer. The field experiment was maize – legumes intercropping whereby the N2 fixation assessment was done 35 days after planting. In both cases, maize (Katumani variety) was the non- N2- fixing reference crop. The legumes formed effective nodules with the native Rhizobia. Different quantities of N2 gas were fixed by the different legumes, the differences being attributed to the legumes’ differences in their genetic characteristics. In the field, monocropped cowpea, pigeonpea and greengram fixed 38, 21, and 49 kg N2, respectively. In the intercrop system cowpea, pigeonpea and greengram fixed 16, 4, and 24 kg N2, respectively. In both cases, the quantities of N2 fixed were less than 50% of their total N accumulation. It was concluded that in Muheza, maize grown in association with the legumes would continue to need supplementation of mineral N fertilizer to maximize its yields.