Soil and water conservation measures and challenges in Kenya; A review

The preservation and sustainable development of soil and water resources is one of the basic principles for the development of Kenya. Throughout the course of history, all the social improvement and economic development are deeply concerned with soil loss and ecological environmental protection. Poor soil and water conservation measures will lead to land degradation that are either natural or human induced. Natural hazards include land topography and climatic factors such as steep slopes, landslides from frequent floods, blowing of high velocity winds, rains of high intensity, strong leaching in humid regions and drought conditions in the dry regions. It is now common sense that soil and water conservation is the insurance for national ecology and its development. Consequences to land degradation leads to increased use of inputs and greater costs where farmers attempt to combat reduction in yields with increased inputs, particularly fertilizers. For the past long period of time, soil and water loss has been recognized as number one killer to the ecological environment and Kenya is at critical conditions for its development with complicated geological conditions and accelerated human destruction and serious soil and water losses. Based on historical documents, experience and detailed data analysis, this paper aims to review the general characteristics of soil and water loss, to explore the relationship between soil and water conservation and sustainable economic development, and to provide relevant strategies for soil and water conservation in Kenya. * Corresponding Author: George Njomo Karuku  gmoe54321@gmail.com International Journal of Agronomy and Agricultural Research (IJAAR) ISSN: 2223-7054 (Print) 2225-3610 (Online) http://www.innspub.net Vol. 12, No. 6, p. 116-145, 2018 Int. J. Agron. Agri. R. Karuku. Page 117 Introduction The Republic of Kenya, is in Africa and a founding member of the East African Community (EAC) with the capital city Nairobi. Kenya's territory lies on the equator and overlies the East African Rift covering a diverse and expansive terrain that extends roughly from Lake Victoria to Lake Turkana (formerly Lake Rudolf) and further south-east to the Indian Ocean. It is bordered by Tanzania to the south and southwest, Uganda to the west, South Sudan to the north-west, and Ethiopia to the north and Somalia to the northeast. Kenya covers 581,309 km2, and current population of 50,410,740 as of Saturday, January 27, 2018, based on the latest United Nations estimates, of which 74% lives in rural areas. Average population density is 87 per km2, but its distribution is highly influenced by climate and agro-ecological zone. The highest density is found in western province. From 2002, the population growth rate was estimated at 1.8 5 per year. Life expectancy increased up to 60 years by 1993 but dropped to 45 years by 2002 due to high incidence of HIV/AIDS (AQUASTAT-FAO, 2005). Overall, poverty level was estimated at 30.8% in 2004. Improved water sources are accessible for 62% of the population, ranging from 89 % in urban areas to 46% in rural areas. Improved sanitation facilities are used by 56% of the population in urban areas and 43% in rural areas, while average over the whole country is 48% (AQUASTAT-FAO, 2006). Kenya has a warm and humid tropical climate on its Indian Ocean coastline and cooler in the savannah grasslands around the capital city, Nairobi, and especially closer to Mt Kenya, which has permanent snow on its peaks. Further inland are highlands in Central and Rift Valley regions where farmers grow tea and coffee as cash crops and are major foreign revenue earners. To the West are Nyanza and Western regions, with an equatorial, hot and dry climate which becomes humid around Lake Victoria, the largest tropical fresh-water lake in the world. This gives way to temperate and forested hilly areas in the neighbouring western region. The north-eastern regions along the border with Somalia and Ethiopia are arid and semi-arid lands (ASALs) with neardesert landscapes. Kenya is known for its world class long distance athletes in track and also field events and rugby. Its diverse climate and geography give rise to expansive wildlife reserves, national parks and white sandy beaches at the Coastal region making Kenya home to the modern safari. Kenya has several world heritage sites such as Lamu, Diani, Bamburi and Kilifi, where international yachting competitions are held every year as well as being the cradle of mankind in Lake Turkana where oldest fossils for early man were first discovered. The Kenya economy is the largest by GDP in East and Central Africa (IMF, 2011 a & b). The capital, Nairobi is a regional commercial hub. Agriculture is a major employer with country’s traditional exports of tea, coffee and fresh flowers to Europe. Soil types The soil types in the country vary from place to place due to topography, amount of rainfall and parent material. In western Kenya the soils are mainly; Acrisols, Cambisols (WRB, 2014) and their mixtures, are highly weathered, leached and with high accumulation of Iron and Aluminum oxides. The soils in Central Kenya and the highlands are mainly Nitisols and Andosols, are young and of volcanic origin. The arid and semi-arid lands (ASALs) comprise of Vertisols, Gleysols and Phaozems (WRB, 2014), and are characterized by pockets of sodicity and salinity, low fertility and are vulnerable to erosion. Coastal soils are coarse textured and low in organic matter; the most common type being Arenosols, Luvisols and Acrisols. Widespread soil salinity, which has adversely influenced irrigation development is found in isolated pockets around Lake Baringo basin in the Rift Valley and in Taveta division of the coast region (AQUASTAT-FAO, 2006). Rainfall and Agro-ecological zones Average annual rainfall is 630mm with a variation from less than 200mm in northern Kenya to >1,800mm on the slopes of Mt. Kenya. Rainfall distribution pattern is bimodal with long rains falling from March to May and short rains from October to November for most parts of the country. The climate is influenced by the Inter-tropical Convergence Zone and relief, and ranges from permanent snow above Int. J. Agron. Agri. R. Karuku. Page 118 4,600m on Mt. Kenya to true desert type in the Chalbi desert in Marsabit district, north of the country. About 80% of the country is ASAL, while 17% is considered high potential agricultural land, sustaining 75% of population. Forest cover is about 3% of total land area. The country has six major agroecological zones namely: Upper highland (UH), lower highland (UH), upper midland (LM), lower midland (LM), lowland (L) and coastal lowlands (CL). These zones are associated with corresponding temperature variations ranging from freezing to 400C. The Penman estimate of annual evaporation from open water surfaces in Kenya varies from 1000mm in Central highlands to 2,600mm in arid north. According to AQUASTAT-FAO (2006), agricultural land covers 33% of the country and is classified as (i) high potential land receiving more than 850mm of annual rainfall, 67,850km2 (ii) medium potential land receiving 850-730mm; covering 31,570km2 (iii) low potential land receiving less than 610mm, covering 42,050km2 (iv)other lands covering 48,670km2. Soil water conservation The United Nations predicts that 1.8 billion people will experience absolute water scarcity in less than 5 years, and worry that by 2025, two out of three persons will be living in water-stressed regions. Already every five persons worldwide cannot access their basic everyday water resource, a fact recently witnessed in Cape Town, South Africa which is in dire need of water with serious rationing of the commodity. Water may well be a renewable resource, but its capacity to renew itself depends on how it is managed. Man faces serious water management crisis according to the Pacific Institute book in its world water series (Haughn, 2009). Increasing efficiency in use and reducing wastage in water systems is quite often the cheapest, easiest way for us to get new water, something that is mostly ignored in future water planning programs the world over (Gleick, 2009). Poor management of resources such as unplanned land clearing for cultivation and deforestation of the water towers has led to serious environmental and ecological degradation as well as reduced water volumes. In Kenya, hiving of forest land for political expediency plus illegal invasion and settlements in large swathes of forests at Hombe and Timau in Mt Kenya, Ngong forest, Masaai Mara and Aberdare ranges among others has led to erratic and low rainfall experienced in the maize and wheat growing belts of Kenya as well as in the Game reserves and national parks where the rivers are drying up (Plate 2b&3). The dwindling water resources as the rivers dry has led to migration of the famous flamingo birds from L. Nakuru hence affecting ecotourism in the bird sanctuary. The Masaai Mara Game Reserve that was once voted the seventh wonder of the world due to the wildebeest seasonal migration every year is experiencing challenges as the Mara river shrinks and the crocodiles and other wildlife unable to thrive and flourish. Some lakes like Kamnyarok in the same belt have dried up leaving a trial of death and devastation in their wake. Kipsang (2015) in an article in the standard newspaper bemoaned the human activity threatening important water towers in Kenya especially Kaptagat (Plate 1) that forms part of the Mau complex (Plate 4). Fig. 1. A man with fired wood collected in Kaptagat forest, Mau complex. On a national scale, accelerating deforestation (Plate 4), soil erosion and environmental degradation remain a major concern. Water resources are under pressure in parts of the country owing to overuse, not only for agricultural and domestic consumption but also for hydro-power and wildlife. Ecological disruption of inland lakes, particularly Lakes Victoria, Turka


Introduction
The Republic of Kenya, is in Africa and a founding member of the East African Community (EAC) with the capital city Nairobi. Kenya's territory lies on the equator and overlies the East African Rift covering a diverse and expansive terrain that extends roughly from Lake Victoria to Lake Turkana (formerly Lake Rudolf) and further south-east to the Indian Ocean. It is bordered by Tanzania to the south and southwest, Uganda to the west, South Sudan to the north-west, and Ethiopia to the north and Somalia to the northeast. Kenya  Kenya is known for its world class long distance athletes in track and also field events and rugby. Its diverse climate and geography give rise to expansive wildlife reserves, national parks and white sandy beaches at the Coastal region making Kenya home to the modern safari. Kenya has several world heritage sites such as Lamu, Diani, Bamburi and Kilifi, where international yachting competitions are held every year as well as being the cradle of mankind in Lake Turkana where oldest fossils for early man were first discovered. The

Kenya economy is the largest by GDP in East and
Central Africa (IMF, 2011 a & b). The capital, Nairobi is a regional commercial hub. Agriculture is a major employer with country's traditional exports of tea, coffee and fresh flowers to Europe.

Soil types
The soil types in the country vary from place to place due to topography, amount of rainfall and parent material. In western Kenya

Rainfall and Agro-ecological zones
Average annual rainfall is 630mm with a variation from less than 200mm in northern Kenya to >1,800mm on the slopes of Mt. Kenya. Rainfall distribution pattern is bimodal with long rains falling from March to May and short rains from October to November for most parts of the country. The climate is influenced by the Inter-tropical Convergence Zone and relief, and ranges from permanent snow above Karuku. Page 118 4,600m on Mt. Kenya to true desert type in the Chalbi desert in Marsabit district, north of the country.
About 80% of the country is ASAL, while 17% is considered high potential agricultural land, sustaining 75% of population. Forest cover is about 3% of total land area. The country has six major agro- According to AQUASTAT-FAO (2006), agricultural land covers 33% of the country and is classified as (i) high potential land receiving more than 850mm of annual rainfall, 67,850km 2 (ii) medium potential land receiving 850-730mm; covering 31,570km 2 (iii) low potential land receiving less than 610mm, covering 42,050km 2 (iv)other lands covering 48,670km 2 .

Soil water conservation
The United Nations predicts that 1.8 billion people will experience absolute water scarcity in less than 5 years, and worry that by 2025, two out of three persons will be living in water-stressed regions.
Already every five persons worldwide cannot access their basic everyday water resource, a fact recently witnessed in Cape Town, South Africa which is in dire need of water with serious rationing of the commodity. Water may well be a renewable resource, but its capacity to renew itself depends on how it is managed. Man faces serious water management crisis according to the Pacific Institute book in its world water series (Haughn, 2009). Increasing efficiency in use and reducing wastage in water systems is quite often the cheapest, easiest way for us to get new water, something that is mostly ignored in future water planning programs the world over (Gleick, 2009 For L. Baringo, the situation has been aggravated by poor land use resulting in siltation and output from fishing and forestry sectors in particular has declined substantially due to resource degradation (Kinyali et al., 1996) (Kocyigit, 2012). For most wetlands, soil erosion by water is the most common process causing sedimentation downslope and on riverine valleys meaning there is a distinct linkage between erosion and watershed conservation (Stocking and Niamh, 2000), and these are accelerated by deforestation, overgrazing, and the cultivation of unsuitable or fragile land (Lal, 1988 , which has recently been declared an endangered water body by the regional government of Kenya (NEMA, 2007). So far, few studies have been carried out on the spatialtemporal lands cover changes possibly affecting the size of L. Ol'Bolossat hence lack of reliable in-situ data. Accumulation of organic matter and silt from the surrounding farmlands have contributed to water pollution and fluctuation of water level from zero to 250cm depending on rainfall, surface run off and seepage from the basin (Wamiti et al., 2007). The lake suffers domestic and agricultural pollution due to unsustainable farming practices that lead to occurrence of waterborne diseases (Ruhiu, 2000 Karuku.
Page 121 The use of agrochemicals in neighbouring farms has led to bioaccumulation in fish and pose health risk to human as well as fish death and causes extinction of some species (GoK, 2009b    In the management (Okech, 2010 Soil and water conservation, however, is now embraced as a tool for the management of soil and water land resources in order to satisfy the needs of the land users through sustained agricultural production (Mutunga, 2001).

About 80% of Kenya's land mass is ASAL and
supports 35% human and 50% livestock populations (Mutunga, 2001). In Kenya, the severity of soil erosion was realized as early as the 1920s. In an attempt to arrest the situation, compulsory terracing schemes were introduced in the 1940s, but they were unpopular because the benefits were unclear to the local people.
Some techniques developed during this period were and are effective but the fact that they were based on enforced communal work meant that soil conservation was bitterly resented by the local people (Critchley, 1991;Tiffen et al., 1994). Many terraces fell into disrepair around the time of independence (1961) and indeed the programs catalyzed resistance and armed struggle against the colonial regime (Beinart, 1984;Anderson and Grove, 1987 Erosion was worsening due to the expanding cropped area while draught spells regularly affected yields, especially maize. Enforced conservation did not work in colonial times but in the 1970s people were ready to respond to new campaign as they envisaged accrued benefits to their efforts. This implied that awareness and communal participation in decision making bore fruits that were lacking in pre-colonial times, Machakos has the reputation for being the district with the best soil and water conservation in Kenya (Critchley, 1991

Terraces
Leveled bench terraces and earth banding on existing slopes are common earth structure in Kenya.
Sometimes, and especially in the highlands, steps are constructed across hillsides and strips of crop residues are covered with soils dug from above. The resulting incorporation of organic matter increases soil fertility and enhances infiltration (Thomas, 1988) through macro porosity as well as increased water retention in soils (Karuku et al. 2012;2014). The fanya juu earth bunding system is now modern tradition in Kenya (Critchley et al., 1994). The fanyajuu terrace (Plate 8) are designed to trap run-off and suspend sediment. A trench is dug and soil thrown upslope to form an embankment which is very effective in trapping runoff and there is evidence crop performance is increased (William and Hess, 1999).
The challenge however, is the high labor requirement in their construction and maintenance (Kiome and Stocking, 1993). to the organic carbon pool. This has the added advantage of holding more moisture after rains especially in these ASALs and improving soil friability and resilience. Yields have been observed to increase tremendously in these low rainfall areas and a promise to food security in the region.

Cover crop for soil fertility and erosion control
Cover crops is any annual, biennial or perennial plant grown as a mono-or poly-culture to improve any number of conditions associated with sustainable agriculture (Lu et al. 2000). Cover crops are fundamental sustainable tools used to manage soil quality (Mannering, et al. 2007;Birte et al., 2008), water, weeds, pests, diseases and diversity in an ecosystem. Keeping the soil covered is a fundamental principle of conservation agriculture. Crop residues are left on the soil surface to protect soil surface after harvesting or during kill-down when the cover crops are slashed and left in the field at flowering (Karuku, 2012;Karuku et al., 2014). Additional cover crops may be needed if the gap is too long between harvesting one crop and establishing the next. Cover crops improve the stability of the conservation agriculture system, not only on the improvement of soil properties but also for their capacity to promote an increased biodiversity in the agro-ecosystem (Yadev et al., 2000;Prasad et al., 2002). Cover crops are beneficial in stabilization of soil moisture and temperature, protect the soil during fallow periods, mobilize and recycle nutrients, improve the soil structure and break compacted layers and hard pans (Mannering, et al. 2007;Birte et al., 2008), permit a rotation in a monoculture, control weeds and pests and produce additional soil organic matter that improve soil structure.

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Cowpea (Vigna unguiculata) for example is an important grain legume in the tropics and subtropics and is an ideal cover crop due to its drought tolerance, grow even in very poor soils with very little water and fix di-nitrogen from the atmosphere. It yields eatable grains and can be used as an animal fodder rich in protein.
Agro-ecosystems are ecological systems managed by humans across a range of intensities to produce food, Cover crops use water during their cycle in the farm and thus affect water relationship of the next crop (Unger et al., 1998;Gachene and Mwangi, 2006).
Effects are positive when cover crops are managed to improve infiltration and reduce evaporation (Karuku et al., 2014), or remove water from waterlogged soil to allow timely establishment of the next crop. The effect could be negative when cover crops limit water for the next crop or aggravate a wet soil condition (Unger et al., 1998). Cover crops have an influence on physical soil properties such as water relationships, aggregation, infiltration capacity, bulk density, soil temperature and hydraulic conductivity. Cover crops influence soil water content through reduced surface evaporation due to mulch effect and increased infiltration and retention of precipitation (Smith et al., 1987;Karuku et al., 2014). Judicious use of cover crops residues, either incorporated in the soil or placed on soil surface can help in maintaining adequate infiltration rates (Adekalu et al., 2007), preventing soil surface crusting (Summer and Stewart, 1992), improving soil aggregation (Haberhauer et al., 1998;Le Bissonnais and Arrouays, 1997), modifying the transport and retention of water (Karuku et al., 2014), heat (Bristow and Campbell, 1986;Bussiere andCellier, 1994, Dahiya et al., 2003) and aeration in soil (Larson et al., 1978). Mannering and Mayer (1963) found that final infiltration rates into a typic Argindoll were increased from 2.3 to 5.3 cmhr -1 when 2. Once worked into the soil, the fresh plant material rapidly releases nutrient and become fully decomposed within a short period of time (Gachene and Mwangi, 2006;Karuku et al., 2014). Aged or coarse material such as straw and twigs decompose at a slower rate than fine material and therefore contribute to the buildup of SOM content (Bivision, 2009). An alternative to sowing a green manure crop in the field is to collect fresh plant material from elsewhere and work it into the soil (biomass transfer) as done by Rutunga et al. (1999) in Western Kenya.
He observed that trees and /or shrubs growing alongside crops in agro-forestry systems could provide large quantities of green material which can be used as green manure. Tithonia diversifolia for example, accumulates high concentration of nutrients in its leafy biomass, which then mineralizes very rapidly when incorporated in the soil. Green leaf biomass of Tithonia diversifolia harvested in Western Kenya is high in nutrients, in order of 3.5-4.0% N; 0.35-0.38%P; 3.5-4.1%K; 0.59%Ca and 0.27%Mg on dry matter basis (Rutunga et al., 1999). In many areas, most of the fruits produced end up rotting in the field due to these setbacks. Recently

Agro-forestry in Kenya
Makueni County have seen tremendous improvement in the same after setting a processing fruit factory that is benefiting many farmers in the area (www.makueni.go.ke/makueni-fruit-processing-plantopened). These are institutional innovations for better managing the complex nexus between poverty, food security, and natural resource management in the dry lands such as in Kenya (Jama et al., 2006).
Traditional agroforestry systems take the form of trees scattered on crop fields, woodlots, homestead tree planting and multi-storey home gardens (Eyasu, 2002 (www.worldagroforestry.org/news/reaping-rewardsagroforestry-kenya). Planting trees and shrubs on earth structures such as soil and stone bunds, terraces and raisers combines soil conservation with production of various products such as fodder, fruits and fuel wood. This has made the land to be utilized more productively as trees use the area along the structures where crops cannot be grown. The challenge to guard against is some of the species introduced for soil conservation becoming invasive weeds such as Prosopis juliflora which was a very good fodder initially but has now become ecological disaster in the ASALs of northern Kenya (Sanchez and Jama, 2000).

Hedges
Hedges are used to conserve soils in Kenya on a contour. A contour hedge is a horizontal strip of multipurpose trees or shrubs that is used to control soil erosion on sloping lands. These hedges provide high quality fodder (e.g. Lucerne hedges), firewood, stakes for climbing beans and mulch material to conserve soil moisture in the field.

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Contour hedges control erosion by providing a physical barrier as well as through increased water infiltration as a result of leaf litter layer creating good soil structure. Over the long-term, these hedges have resulted in the formation of terraces on the upper side of each hedge (Jama et al., 2006), an added advantage in soil and water conservation measures.

Improved fallows
Improved fallows have been used in some areas, where land is left to rest (fallow) from cultivation and is enriched with leguminous trees to speed up soil fertility replenishment. and Cajanas cajan were used to rapidly replenish soil fertility in one or at most two growing seasons (Jama et al., 2006). A maximum of 3 years have been cited as necessary to replenish fertility in extremely degraded soils through improved or planted fallows (Kwesiga and Chisumpa, 1992).
The trees and shrubs are interplanted with crops such as maize during the rainy season and are left to grow during the dry season tapping soil water with their deep taproots. Right before the next rainy season, farmers harvest the fallows, remove fuel wood and incorporate biomass (leaves, soft stems and leaf litter) into soil prior to planting maize in Eastern Kenya.
In western Kenya, maize yield following improved fallows averaged 4.1Mgha -1 which is much higher than those from non-fertilized plots continuously planted with maize at 1.7Mgha -1 (Sanchez et al., 1997;ICRAF, 2003 Better soil conservation results have been achieved when fallows were combined with contour hedges planted to fodder species (Sanchez and Jama, 2000).
It can therefore be argued that productivity on degraded lands can be restored and food security effectively achieved with conservation practices country wide. In a survey in western Kenya, over 16,000 farmers were using improved fallow in 2000 (Sanchez and Jama, 2000). The only challenge now is the increased population which has made it almost practically impossible to leave land fallow for more than a season. This in itself does not allow land to recover and regenerate adequately to realize the accrued benefits of fallowing. But for those in ASALs and with large tracts of land, the benefits cannot be overemphasized.

Vegetation strips
Vegetation strips are usually narrow grass strips grown across slopes. The grass acts as a barrier to runoff thus encouraging deposition of sediments and eventually leading to terrace development.
Species such as Pennisetum purputeum are also used as fodder to draft animals and other livestock hence dual purpose. Live fences surrounding cultivated fields acts as modification of vegetative strips (Thomas, 1988 (Fig. 10, 11, 12).

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Other measures include intensification of grazing land use where fodder crops are planted and used for cut-    The challenge in management measures is that they are not clear-cut, they require great flexibility and responsiveness at initial stages and in subsequent years that follow.

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There are also implications for land tenure that can complicate decision-makings that may sour relationships between neighbours (WOCAT, 2007) as they try to conserve their land holdings.

Contour farming
Contour farming involves ploughing, planting and weeding along the contour, across the slope rather than up and down. Contour lines are lines that run across a hillslope such that the line stays at the same height or altitude and does not run uphill or downhill.
As contour lines travel across a hillside, they will be close together on the steeper parts of the hill and further apart on the gentle parts of the

Trash lines
Trash lines range from simple bunds of cereal and legume Stover to more sophisticated pegged brush lines according to Gichuki (1992). Apart from impeding runoff and enhancing infiltration, trash lines also increase soil organic matter content when incorporated into soil during ploughing, enhance soil macro porosity, water holding capacity, soil hydraulic conductivity as well as improve soil fertility upon decomposition and mineralization (Karuku et al., 2014).  (Okoba et al., 1998;Wakindiki and Ben-Hur, 2002).

Cutoff drains, retention and infiltration ditches
Cutoff drains are usually dug across a slope to intercept surface runoff and carry it safely to an outlet such as a canal or stream with minimal risk to aggravating erosion. They are used to protect cultivated land, compounds and roads from uncontrolled runoff, and to divert water from gulley heads (Okoba et al., 1998).
Retention ditches are dug along a contour to catch and retain incoming runoff and hold it until it seeps into the ground. They are an alternative to cutoff drains when there is no nearby waterway to discharge the runoff into. They are used to harvest water in semi-arid areas.

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Infiltration ditches are one way of harvesting water from roads or other sources of runoff and consist of a ditch, 0.7-1.5m deep, dug along a contour, upslope from a crop field. When it rains, runoff water is diverted from the roadside into the ditch, which is blocked at the end to hold the water. Water trapped in the ditch seeps into the soil and maybe used for rain harvesting agriculture where moisture is stored in the ground. This is has been used in the semi-arid area in Baringo district in the Kenyan Rift Valley area for increased food production (Kinyali et al., 1996).

Broadbeds and furrows
In a broadbed-and-furrow system, runoff water is usually diverted into field furrows 30cm wide and 30cm deep. The field furrows are blocked at the lower end to hold the water and when one is full, the water backs up into the head furrow and flows into the next field furrow.
Between the field furrows are broad beds about 170 cm wide, where crops are successfully grown.

SWOT analysis on soil conservation in Kenya
Soil and water conservation processes in Kenya can be summarized into strengths, weaknesses, opportunities and threats (SWOT) where crop residues are considered herein:-

Strengths The merits of soil conservation includes
Advantages of mulch are similar to those of crop residues in that they increase water infiltration (FAO, 2000;Lal, 1976, Karuku et al, 2014, decrease runoff (Lal, 1976), and have greater soil water availability than such materials as saw dust and wood shavings.

In relation to increasing infiltration, studies in Kenya
reported that in a 12% slope of well-structured freshly cultivated soils, where 4Mgha -1 of grass mulch equivalent to 79% cover reduced runoff from simulated rainfall to 5%. This is an indication that at 80% cover, equivalent to 4Mg ha -1 maize straw, would be appropriate for increasing rainwater infiltration hence its conservation in soil.
Both residues and mulches provide additional benefits, notably less water loss by direct surface evaporation, less weed incidence, softer and more workable soils and increased earthworm activity (Lal et al., 1980;Karuku, 2011;Karuku et al., 2014). After residue incorporation, there are additional nutrients (FAO, 199b;Karuku et al., 2014) released into the soil and subsequently increased yields. In western Kenya, mulching with Tithonia spp has given substantial yield increase of maize (Zea mais), Kale (Brassica oleracea), tomatoes (Lycopersicon esculentum) and French beans (Phaseolus coccineus).
The net profit of mulching kale ranged from USD 91 to 1,665ha -1 (ICRAF, 1997). In the semi-arid areas west and north-west of Mount Kenya, maize yields increased by a factor of 4.4 when 3Mgha -1 of mulch was applied (Liniger, 1990).

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The permanent cover of surface residues encourages soil faunal activity, which in combination with higher soil organic matter contents leads to improved soil porosity (FAO, 1995c  On steep slopes, the application of residue cover crops is not easy and these materials are easily washed downhill.
Mulching cannot be applied after emergence of closely spaced crops as it smoothers them thus interfering with their growth and performance.
Mulching materials and crop residues are often grazed by cattle belonging to the farmer, the community or landowner (in case of tenant farmer), fed to livestock, or sold as fodder hence a conflict of interest amongst competing uses. Sometimes thee materials are in high demand for thatch or fuel.
In ASALs, mulches are rapidly consumed by termites, and in hot humid climates, they decompose rapidly (Karuku et al., 2014).

Opportunities
Runoff control and runoff harvesting produce significant crop yield increases in average years.
Water conservation strategies may therefore allow for earlier planting or be accompanied by increased planting densities, both of which may result in yield increase (Hess and Stephens, 1998). More land maybe brought under agriculture or pastures through water harvesting and erosion control on steep lands.
The outcomes will be higher incomes and better nutrition to the people who are therefore healthy and productive (Kinyali et al., 1996). The environment will also be conserved hence less pollution. Current and on-going research on Prosopis juliflora for biofuel and animal feeds may lead to better utilization of the noxious weed as well as fertilizer formulation from both Prosopis juliflora and Eichornia crassipes (Kiplangant et al., 2018).

Challenges
Conservation measures suggests that population growth and agricultural intensification are compatible with environmental recovery (Tiffen et al., 1994).

Political expediency
Due to political rivalry, forests are usually given to supporters of particular politicians as a bribe or repayment for political patronage.

Macro-economics
Cash crop production for export

Liberalisation
The liberalisation process has put a lot of emphasis on the privatisation of public land and forests resulting in the non-recognition of customary resource tenure.
The Ogieks have been denied their ancestral rights to the forest land they occupy.

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The lower rainfall in semi-arid areas compared with that in humid climates does not mean a corresponding low level of soil erosion by water in these places. Indeed rainfall erosion has been observed to be higher in ASALs than in many other climatic zones. This is partly because the semi-arid areas has a high proportion of convective thunderstorm rain of high intensity and high erosive power. There is also poor protective vegetative cover at the beginning of the rainy season and some of the and spreading the water out over a large area (for example, via contour ditches) and above all, enhance the infiltration of water into the soil by improving the physical soil quality with conservation tillage techniques that aid in percolation.

Integrated Programmes
The current approach by soil conservationists unlike in the 1980s is moving away from using mechanical works and structures in soil conservation programmes that were paid for by a government or donors such as increasing awareness of the ineffectiveness of terracing programmes alone.
Conservationists are now moving towards the view