This category of measures has the primary objective to ameliorate and maintain soil quality. In the context of a changing climate, this improved soil quality entails better water retention and discharge in longer periods of drought and times of extreme rainfall. Besides, the higher yield that restored soils could bring, might be an extra driver for the smallholder farmer to adopt these techniques.
Fanya juu is a technique to reduce soil and water runoff on sloping cultivated land. It consists of earthen or stone banks on the contour, accompanied by a trench along its lower side. The formation of bench terraces is triggered as the land in between several bunds will level off over time (erosion and sedimentation). Soil and rainwater are retained between the bunds. As a result, conditions for crop growth improve immediately – due to increased soil moisture availability – as well as in the long term, due to soil quality conservation (Hailu, Moges, & Yimer, 2012). (WOCAT SLM Technologies, 2019f)
Jessour are a series of hydrological units consisting of three components: the impluvium, the terrace and the dyke. The impluvium is the catchment area for every unit and is bordered by natural water divides. Each impluvium receives and discharges not only rainwater, but also all excess water from upstream units. Over time, terraces start to emerge after sediment is deposited against the built dykes. Agriculture is often practised on these terraces. With artificial soils of over 5 meters deep, these areas are suitable to cultivate fruit trees on.The technique creates levelled agricultural plots, thereby recharging the underlying aquifer, controlling flood water runoff and erosion of soils. The dykes are built with a central or lateral spillway to drain any excess water. The ratio between the area where the harvested water is applied (production area) and the total area from which water is collected (catchment area) is estimated to be 1:5. (WOCAT SLM Technologies, 2019g)
Similar to the Jessour technology, Tabias comprise an earthen dyke that captures runoff, increasing infiltration and reducing erosion ((UNEP-DHI Partnership et al., 2017). Different from Jessour, Tabias have a lateral bund that directs excess runoff water along the dyke. Besides, Tabias sometimes have a small floodwater diversion dyke (image) that directs extra water from a (ephemeral) river or runoff path towards the Tabias, enlarging the catchment size. Trees especially grow well along the spillway lateral to the Tabia, since water infiltrates well there.
The ratio between the area where water is applied (production area) and the total area from which water is collected (catchment area) varies from 1:6 to 1:20. (WOCAT SLM Technologies, 2019h)
Growing with contours
Contour farming entails following the natural elevation contour when ploughing and planting. Doing so creates a water break, which reduces gully formation and loss of water and fertile soil through surficial runoff. The water break reduces the speed of runoff water, allowing it to infiltrate into the soil. (WOCAT SLM Technologies, 2017i; WOCAT SLM Technologies, 2019i)
Placing series of bunds along the natural elevation contour is a way for farmers to promote the formation of rough terraces on sloping lands. The technology aims to control soil erosion, promote water retention, and hence increase crop production in a simplistic manner. Since bunds are permeable structures, they will not pond runoff water, rather they will slow it down to increase the infiltration of water into the soil (UNEP-DHI Partnership et al., 2017).
Bunds can be made out of (bundles of) dry vegetative material, stone piles, earth and/or any organic ‘waste’ like weed or crop residues that is locally available. The structures can be stabilized by planting crops or trees in its direct surroundings. (WOCAT SLM Technologies, 2017j; WOCAT SLM Technologies, 2019j)
Mulching involves covering the soil with mulch (crop residues) after harvesting. Adding mulch to the patch of land at the beginning of the dry season improves infiltration, reduces evaporation of soil moisture and acts as a barrier against wind and water erosion (UNEP-DHI Partnership et al., 2017). While present on the soil, the crop residues will start to decompose and be incorporated into the soil. Soil structure as well as fertility will benefit from this, which again will benefit water retention. Doing so, mulching can be used to overcome rainfall variability. This form of mulching technology can be of added value to multiple measures introduced here.
Another type of mulching uses black plastic to cover the crops. Such impermeable plastic prevents water evaporation. Condense water will drop back to the crop. In combination with precision irrigation, this could improve irrigation efficiency in areas that face long periods of drought. Black, opaque plastic should stop weed growth and the attraction of insects. Both effects (less nutrient competition and insect plagues) are highly favourable for crop growth. Besides, plastic mulch reduces the impact of extreme rainfall on the soil. (WOCAT SLM Technologies, 2017k; WOCAT SLM Technologies, 2018b)
Small pit cultivation
By placing crops or trees in their individual slightly excavated pits, the soil moisture status on sloping lands can be improved due to the retention of water in so called micro-catchments. Besides, sheet erosion can be controlled by protecting the pit with a small earthen or stone bund. In regions with erratic rainfall, this technology uses the rainfall that is present effectively. (WOCAT SLM Technologies, 2019f; WOCAT SLM Technologies, 2019g)
Increase organic matter content
Adding organic fertilizer, and thereby increasing the organic matter content of the soil, boosts biological activity in the soil. As a result, the soil’s capacity to store nutrients and the structure of the soil. An improved soil structure benefits infiltration and retention of rainfall and runoff water (UNEP-DHI Partnership et al., 2017). In short, the productivity of one’s farm will increase – also in longer periods of drought. As organic fertilizer, farmers can use compost that consists of straw pen manure with litter or household waste. (WOCAT SLM Technologies, 2017l; WOCAT SLM Technologies, 2017m)
Conservation tillageConservation tillage is a practice built on three main pillars: (i) minimum soil disturbance, (ii) permanent soil cover and (iii) crop rotation. Where regular ploughing inverts the soil, disturbing its cover and all biological activity, the soil is often stripped under conservation tillage. Alternative practices to prepare the soil for a new growing season are ripping or stripping. Ripping the soil creates small furrows in which manure can be added. Stripping will loosen the soil by lifting it, and letting it fall into its place (image). Both methods however do not invert the soil, leaving crop residues on the surface. As a result, soil structure and microbial activity improves. The soil is less exposed to runoff, and allows for better infiltration of water. Rainfall from events at the beginning of the wet season can be stored in the rooting zone, prolonging the source of soil moisture available to crops in the dry season (UNEP-DHI Partnership et al., 2017). Besides, the rate of evaporation is decreased. These effects can be enhanced by adding mulch to the soil.
In earlier projects in Kenya, yields from small-scale conservation tillage have turned out over 60% higher than under conventional ploughing. Moreover, due to early crop maturity under conservation agriculture, farmers gain market access when prices are still high. Crops are fully grown in earlier, since they can be planted earlier in the season, when under inversion tillage the farmer has to wait for the soil to become moist before ploughing. (WOCAT SLM Technologies, 2017n; WOCAT SLM Technologies, 2018c; WOCAT SLM Technologies, 2019m; WOCAT SLM Technologies, 2019n)