Browsing by Author "Tumbo, S.D."

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Identification of suitable indices for identification of potential sites for rainwater harvesting
(2013) Tumbo, S.D.; Mbilinyi, B. P.; Mahoo, H. F.; Mkilamwinyi, F.O.
Although indigenous and scientific knowledge for locating potential sites for water harvesting technologies do exist, a simple and integrated tool to assist farmers’ support agencies, is missing. A geographic information system (GIS)-based decision support system (DSS) can be a valuable tool for such a task. However, key to such DSS are the factors and their suitability levels, which are not well developed. This study therefore focused on the development of suitability levels for most important factors/parameters for identification of such sites. The factors included rainfall, soil texture, soil depth, drainage, topography and land use or cover. Specific suitability levels were derived from analysis of existing RWH technologies in Makanya river catchment. Results showed that suitability levels of factors differ with different RWH technologies. Suitable areas for ndiva is on steep slopes (18o-30o) with clay soils, stone terraces is on moderately steep slopes (10o – 18o) with sandy clay loam soils, bench terraces (5o-18o slopes, clay or silt clay soils) and “boda” (2o-5o slopes, slit clay or clay soils). It was also found that ndiva, “boda”, stone terrace and bench terrace are located at a distance within 125m from cropland. Testing of the developed parameters using ArcView-based DSS framework showed that 81.4% RWH technologies were located in the very high and high suitability levels, indicating the usefulness of the developed parameters and their suitability levels.
Narrowing maize yield gaps under rain-fed conditions in Tanzania: Effect of small nitrogen dose
(2013) Mourice, S.K.; Rweyemamu, C.L.; Nyambilila, A. A.; Tumbo, S.D.
The wide gap between potential and actual yields of maize in Tanzania, due to low productivity is the major constraint to improvement of food security and livelihood of farmers. The objective of this study was to evaluate the potential of the use of small amount of nitrogen fertilizer as a measure to reduce maize yield gap under rain fed conditions. Field experiments were conducted at Sokoine University of Agriculture, Morogoro during the dry and rainy seasons of 2012/2013 using Maize cultivar PIONEER PHB 3253. The nitrogen application rates were 0 (control), 15 (low N dose) and 80 kg N ha-1 (recommended rate). Three water application regimes were tested. Irrigation water was applied from crop establishment up to; grain filling; 50% anthesis; and between 50% anthesis and grain filling. The treatments were applied in a completely randomized block design, in factorial layout for the dry season experiment. Nitrogen treatments were repeated during the 2012/2013 rain season under rain-fed conditions. Both experiments were replicated three times. In a dry season experiment, the water application regimes significantly (P≤0.05) increase biomass at both 50% and harvest maturity stages. Total tissue N content decreased under nonstressed water regime relative to water-stressed treatments. The interaction between irrigation and nitrogen treatments significantly (P≤0.05) affected grain yield. Application of recommended N rate did not result into yield increase when water was limiting. In the rainy season experiment, recommended N rate resulted in highest biomass at end of juvenile (1 t ha-1), 50% anthesis (7.7 t ha-1) and harvest maturity stages (13.1 t ha- 1). Total tissue N content and grain yield increased significantly with increase in N application rates during the rainy season. Under water stress conditions, low N dose produced an extra 1000 kg ha-1 grain yield over absolute control treatment. Under water stress conditions, recommended N rate, a 54% reduction of yield gap was observed, which could not sufficiently reduce yield gap. However, under adequate soil moisture conditions, recommended N rate attained up to 26% yield gap, suggesting that it would be beneficial to apply nitrogen fertilizer when water is not limiting to close the yield gap. Small nitrogen doses can be an effective strategy towards narrowing yield gaps for resource poor farmers especially in drought prone areas. Further study should be done to extend the results beyond experimental site to test and validate the approach under farmers’ paradigms.