IRRIGATION WATER REQUIREMENTS OF SHARED CENTRE PIVOT SYSTEM FOR SMALLHOLDER FARMERS IN IRINGA TANZANIA

Abstract

The present study was conducted to assess crop water requirements, irrigation schedules and water quality for the shared center pivot system for selected crops of the Ulete Irrigation Scheme in Iringa, Tanzania. The study analyzed four crops: maize, beans, potato, and sunflower, to determine their system capacity requirements in two growing seasons. Water scarcity and poor water quality are the result of climate change and population growth. Since agriculture is the first user of water in Tanzania, utilization needs to be minimized, water resources management improved, and water requirements of selected crops must be scientifically decided. CROPWAT was employed in this research to determine crop water requirements (CWRs) and irrigation schedules for selected four crops. Daily climatic data of fourteen years (January 2006 - December 2019) were analyzed to calculate ETo and the effective rainfall. These data were obtained from the Ifunda meteorological Station in the Rufiji Basin. It is found that the pump capacity of 72 l /s can meet crop water requirements for the first growing seasons when there is rainfall to supplement irrigation. However, the available capacity could not meet the irrigation requirement of the total production of maize, beans, potato, and sunflower, which requires a system capacity of 136 l/s during the dry season. The value of ETo ranges from 3.83 to 6.67 mm/day, with effective rainfall from 1.0 to 141 mm. In the first season (February to June), irrigation demand for maize, beans, potato, and sunflower were 208.9, 157.2, 246.8, and 221.0 mm/dec, respectively, and for the second season (July to November) were 631.8,531.0,708.3, and 657.0mm/dec for maize, beans, potato, and sunflower. The demand of water for crops in the dry season is more and in the rainy season is lower. In the first season (February to June), total gross and total net irrigation demand were 247.4 mm and 210.3 mm for maize, 187.4 mm and 159.3 mm for beans, 466.3 mm and 396.3 mm for potatoes, and 260.0 mm and 221.0 mm for sunflowers. In the second season (July to November), the total gross and the total net irrigation were 727.8mm and 618.7mm for maize, 607.6mm and 516.5mm for beans, 833.6mm and 708.6mm for potato, and 763.9mm and 649.3mm for sunflower. The CROPWAT software was found to be helpful in estimating crop irrigation needs for proper water resource management.