Investigation into the effects of deficit irrigation on potato production in Dedza district-Malawi.

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Chikankheni, Aina Tennson
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The University of Zambia
Deficit irrigation strategies in furrow irrigation are important means of saving irrigation water in areas with poor water management. This study was conducted to establish the strengths and weaknesses of the current irrigation practices in Dedza district, to evaluate effects of alternating deficit, fixed deficit, and conventional furrow irrigation strategies on water saving, potato yield and profitability of potato production under different maximum allowable soil moisture depletion levels. The study was done in Dedza district in Malawi. Farmer plot size in irrigation schemes are limited to 0.22 ha of which 81% use gravity-fed canals to convey water with furrow as a dominant irrigation method due to its many advantages. The Certified potato variety “Violet” seeds were used as study material during the experiment which was laid out as a randomized complete block design. It involved three maximum allowable depletion (MAD) levels of 20, 40, and 60% in which furrow irrigation strategies of (i) conventional furrow irrigation (CFI), (ii) alternate furrow irrigation (AFI), and (iii) fixed furrow irrigation (FFI) were applied. A total of 10, 6, and 5 irrigation events were scheduled for the whole season under 20%, 40%, and 60% depletion levels respectively. Compared to the control (CFI), the results showed that AFI and FFI under 20% MAD, saved 30% and 39% of water with slight crop yield reductions of 6% and 14% respectively. Moreover, under 20% MAD, farmers could achieve 17.8% and 7.3% gross margins above the average national value of US$8119.20 with AFI and FFI respectively. Compared to 2.8 US$/m3 for the control, the economic water productivity increased by 39% and 46% for AFI and FFI respectively under the 20% MAD. This research showed that managing the potato crop using AFI or FFI under 20% MAD could allow a farmer in Dedza district to achieve potato tuber yields above the national average while saving water to increase the irrigation scheme membership. The result can be used as the starting point for further research and development of policies that aim at improving potato farmers’ irrigation water and land productivity.
Thesis of Master of Engineering in Agricultural Engineering.