• Cultivated (cropped) area: The soil condition of the cropped area must be well prepared to reduce any soil related limitations for optimum crop establishment and growth
• Catchment Zai pits as a water harvesting technology integrates a variety of factors to avail moisture to the growing crop to attain physiological maturity as follows:
Yield per acre is 30 bags @ KES 2000 translating to a gross income of KES 60,000
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Cost of 10 kg seed
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@140
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1,400
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Cost of 1778 Zai pits distributed into 6 seasons
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@30
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8,890
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3 x 50 kg fertilizers
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@2500
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7,500
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593 debes of FYM (each debe serves 3 pits)
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@10
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5,930
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8 m/days of weeding
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@200
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1,600
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Insecticides
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Assorted
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2,000
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8 m/days of harvesting
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@200
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1,600
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2 m/days dusting and spraying
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@200
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400
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30 gunny bags
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@50
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1,500
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10 m/days threshing and
winnowing
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@200
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2,000
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Total variable costs
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32,820
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-32,800
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Gross margin
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27,180
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• Cultivated (cropped) area: The soil condition of the cropped area must be well prepared to reduce any soil related limitations for optimum crop establishment and growth
• Catchment area: This must be sufficient to generate the extra moisture required in the form of runoff. A Catchment cropped area ratio of 3:1 has been found appropriate.
• Catchment characteristics: As much as possible the catchment should be modified to minimize infiltration. This may be achieved through increasing the catchment gradient towards the cropped area and compaction.
• Efficiency: In order to optimize the crop yield, both the normal rains and the runoff that collects at the cropped area must be used efficiently by the crop. All moisture losses must be minimized. The right crop variety with vigour must be planted early enough to gain from all the moisture experienced at the cropped area. It is advantageous to plant with Phosphorus containing fertilizers for early crop root establishment. Top dressing with Nitrogen and use of farm yard manure for provision of extra nutrients and moisture retention is necessary. Since weeds will compete for moisture and nutrients, weed control will be of necessity. Use of mulch will reduce evaporation losses. In addition since a health crop will use the soil resources efficiently, it will be necessary to protect the crop against pests and diseases.
Zai pits dimensions and lay out
For proper crop rooting zone Zai pits for Maize must have a minimum of 30 cm depth. They may be circular with varying diameters or varying square sizes depending on the anticipated number of plants per pit. A square Zai pit measuring 75 x 75 x 45 (cm) is ideal for 9 maize plants in Kyuso. They are convenient to dig and the sub soil is used to form a soil bund 15 cm high around the catchment area, while the top soil is returned and mixed with farm yard manure at a ratio of 4:1. Less manure ratio could be used depending on the top soil quality, manure availability and complementary use of artificial fertilizers.
Economics
An acre will accommodate 1778 nine plant pits each measuring 75 x 75 x 45 (cm) with a catchment area 3 times its size or 1.7 M2 and a plant population of 16000. At the minimum the yield from one pit will be 1.5 kg which translates to 30 bags of maize from one acre.
Conclusion
Going by the current market prices of maize, it is profitable to invest in water harvesting for maize production in the ASAL. During times of relative low prices, the margins will go lower. However the intervention will have other advantages like food security and employment creation. The area being a livestock zone the maize Stover will be used as livestock feed. The
intervention has a positive environmental impact in that it
effectively brings runoff under control.
Income statement for maize production through Zai pits
