Tuesday, May 8, 2012


Women digging Modified Zai pit holes in Mivukoni, Kyuso, Kenya
Maize is one of the most popular crops in agro ecological zone LM4 in Kyuso district. Kyuso district experiences an average annual rain fall ranging 300 to 600 millimeters in two seasons per year. Due to the erratic nature of the rains, there is a crop failure for 3 in every 5 consecutive seasons. This calls for water harvesting as an intervention to address the moisture shortage that causes the inherent crop failure.

Modified Zai pits
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:
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.

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.
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
Yield per acre is 30 bags @ KES 2000 translating to a gross income of KES 60,000
Cost of 10 kg seed
Cost of 1778 Zai pits distributed into 6 seasons
3 x 50 kg fertilizers
593 debes of FYM (each debe serves 3 pits)
8 m/days of weeding
8 m/days of harvesting
2 m/days dusting and spraying
30 gunny bags
10 m/days threshing and
Total variable costs
Gross margin