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The Zay is made on land which is not very permeable so that runoff can be collected. Zai are holes dug approximately 80 cm apart to a depth of 5 to 15 cm, with a diameter of between 15 and 50 cm (Figure 1). Zai improve infiltration of the captured runoff. The holes are deepened each winter. Improvements in the traditional pits by the addition of fertilizer and organic matter (compost) have resulted in dramatic improvements in yield.