Assessment of irrigation water productivity in Mkoba Scheme in Midlands Province and Silalatshani Scheme in Matebeleland South Province, Zimbabwe
Description
Field measurements were done to quantify amount of irrigation water being applied. Data on yields harvested, amount of water being received from reservoir(s) and planting times was gathered from records of farmers and Departments of Irrigation and Agricultural Extension Services (AGRITEX). Average climatic conditions and crop water requirements were estimated using CLIMWAT 2.0 and CROPWAT 8.0. Data analysis was done using equations as well as Microsoft excel and Statistical Package for Social Sciences (SPSS) version 23 to produce tabulations, descriptions and graphs. Substantial water losses, in both Mkoba Irrigation Scheme and Silalatshani Irrigation Scheme due to the dilapidated irrigation infrastructure, were noted. Maize crop productivity was low, ranging below 50% of the national expected yield of 10-13 tonnes/ha. The collected data further indicated that physical water productivity for maize, beans and wheat was 1.1 kg/m3, 0.54 kg/m3 and 0.87 kg/m3 respectively in Mkoba Irrigation Scheme. Mkoba Irrigation Scheme had higher physical water productivity compared to Silalatshani Irrigation Scheme which had 0.35 kg/m3 for maize, 0.28 kg/m3 for beans and 0.45 kg/m3 for wheat. This suggests that shortages of water under gravity-fed smallholder irrigation increases water productivity as farmers would be conserving it more compared to a situation where the water would be in full supply. In Silalatshani Irrigation Scheme, the economic water productivity for maize was US$0.13/m3, US$0.42/m3 for beans and US$0.23/m3 for wheat. Water productivity was low in both irrigation schemes given the physical water productivity range of 0.3 – 2.0 kg/m3 for maize.