Assessment of water productivity trends for parastatal agricultural operations-case of Middle Sabi Estate, Zimbabwe

Parastatal agricultural operations are central to Zimbabwe's thrust for strategic crop production, more so with its recent agrarian and land reform exercise. This paper presents the results of a study to quantify field water productivity (WP) at ARDA Middle Save Estates in the Save Catchment in Zimbabwe over a 5-year period (1998-2002) for winter wheat and cotton. The field-scale WP indicator, which was determined from crop output and total water supplied (irrigation and effective precipitation) to the field, was selected because it is more appropriate and easy to interpret by management. Middle Save Estates, measuring about 4800 ha and sub-divided into 10 sections each measuring 480 ha, grow a wide range of crops under sprinkler irrigation, but wheat and cotton are grown consistently as nationally strategic crops. The mean WP of winter wheat ranged from 0.49 kg/m3 to 0.60 kg/m3 with an insignificant downward trend over the 5-year period. For cotton, the WP averaged 0.09 kg/m3 to 0.33 kg/m3 with a downward but significant trend (p < 0.034) over the 5-year assessment period. For both crops the WP levels are lower than international averages for comparable situations indicating the need for Middle Save Estates to put into practice measures to raise WP levels. Some of these measures include better crop management, irrigation scheduling, deficit irrigation, change in irrigation technology, and servicing of irrigation equipment.