Browsing by Author "Bjerkholt, J. T."

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Evaluation of the effectiveness of commonly used irrigation scheduling approaches on land and water productivity
(2008-06) Kihupi, N.; Tarimo, A. K. P. R.; Bjerkholt, J. T.; Mkoga, Z. J.; Mbozil, A. F
A field experiment was conducted to study the impacts of different irrigation schedules on land and water productivity of a bean (Phaseolus vulgaris L.) crop. Three irrigation scheduling methods were evaluated using a randomised complete block design., one based on historical climatic data (water balance), a second one based on neutron probe soil moisture measurements and the third one based on normal practices of farmers in the area (farmer-managed schedule). Irrigation water applications and crop water use were monitored throughout the growing season. The mean total water delivery under farmer- managed plots was 735mm which is more than adequate for a bean crop whose water requirement for maximum production varies between 300 and 500mm depending on climate. There were significant differences (P<0.05) in irrigation water productivity (IWP) and field water application efficiency (FAE) among treatments. The IWP and FAE of farmer-managed schedule were significantly lower than the other treatments, but the F AE of the control plot and climatic data plot did not differ significantly (P < 0.05). On the other hand, there was no significant difference (P<0.05) in physiological water use efficiency (PWUE) among treatments. Land productivity was significantly higher (P < 0.05) in the climatic data based schedule than the other methods. It would thus appear that the water budget technique based on average climatic data is a suitable irrigation scheduling criterion which saved irrigation water while achieving maximum yield, optimum water productivity and field application efficiency. Low field application efficiencies under farmers' management practices indicate a need for improvement in water management strategies of individual farmers. This would go a long way to improving both water and land productivities.
Evaluation of the effectiveness of proportioning water Division Weirs in Herman Canal farmer-managed irrigation scheme, usangu plains, Tanzania
(Divion of Research & Development Ministry of Agriculture and Cooperatives, 2008-06) Kihupi, N.I.; Tarimo, A.K.P.R; Bjerkholt, J. T.; Mkoga, Z.J.; Siwalel, S.
In Tanzania, irrigated land is less than 5% of the cultivated area much of which being under traditional irrigation systems. Unfortunately, water in agriculture is indeed too often misused and mismanaged due to lack of know-how of people and weakness of institutions. This study therefore aimed at evaluating a simple approach for equitable distribution of irrigation water using proportioning water division weirs with a view to improving system performance in general. Five proportioning water division weirs were constructed along the main canal to deliver water to eight branch canals of a typical farmer-managed irrigation scheme. Flows to each of the branch canals were measured using calibrated staff gauges. The discharge data along with climatic and crop data were used in the computation of various irrigation performance indicators. Results showed productivity to be rather low, which was attributed to low-level use of inputs including sub-optimal cropping intensities. The relatively low values of output per unit irrigation supply suggest that the efficiency with which water was being used in the scheme is rather low. Overall, equity of water supply (FE = 0.14; AU = 0.52) appeared to be fair, which was an improvement over past experiences before installation of the proportioning weirs. However, in spite of improvements in water distribution, farmers still lacked basic understanding of irrigation scheduling which led to some areas being over-irrigated while others faced water shortage.