13.8: Community Shared Center Pivot Systems

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Since the cost of a center pivot increases proportionally with the length of the pivot, but the area irrigated increases proportionally with the square of the pivot length, the cost of the pivot per unit of land area ($/ha or $/ac) is lowest for large (longer) pivots. Therefore, pivots have been widely adopted on large fields (e.g., 60-70 ha). However, a large pivot can also be used to irrigate several small fields. This approach is being implemented on some smallholder farms in Sub-Saharan Africa (Figure 13.16; Chandra, 2020). Application depths can easily be changed for different sectors, either by changing the pivot speed for different angles in the pivot panel or using speed control VRI. Changing application depths enables the shared pivot to accommodate various crop types and planting dates in different sectors. It is ideal if fields within a sector all have the same crop and planting date, resulting in similar irrigation needs. It is conceivable that zone control VRI could be used to provide unique irrigation management for many small fields of any shape and size, although zone control increases the complexity of the system and the level of management required. A shared center pivot required water users within the pivot to cooperate in a way similar to an irrigation district with canals for water deliver.

Figure 13.16. Shared center pivot irrigation systems for smallholder farms in Rwanda. (Photo courtesy of Ankit Chandra, DWFI.)

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