**1. Introduction**

Land is considered a valuable natural resource around the world and a key factor in production that provides essential agro-ecological services such as food, fodder, energy, and fiber for human life. However, over-exploitation of land for ecosystem services and income generation has resulted in extensive land degradation, persistent degradation of biological productivity and ecological integrity, and loss of human value [1, 2]. More than a fifth of the world's total land area is already degraded due to years of unsustainable land-use practices, land-use changes, and extreme weather events [3]. In some parts of the world, soil fertility, biodiversity, ecosystem services, and productivity have decreased significantly [4]. Recent studies have indicated that more than half of all fertile soils in the world are now classified as highly degraded, with 25–40 billion tons lost annually [5].

In Sub Saharan Africa (SSA), land degradation is estimated to affect about 67% of the total area of land (16.1 m km2 ) with varying degrees of severity [6]. The main direct drivers contributing to land degradation in SSA include unsustainable agricultural practices, over-grazing of livestock, over exploitation of forests and woodlands [7]. In addition, a number of waterways in SSA have been subject to significant pressure, particularly in the semi-arid and sub-humid zones where rivers are overexploited and eutrophication is prevalent [8]. Shiferaw et al. [9] attributed poor land and water management in SSH to the increasing population growth coupled with poor or inadequate incentive structures for local resource managers, climate change and rampart poverty.

In Kenya, recent studies show that 12–15% of the country's total land area, supporting 27% of its population, is suffering from severe to very severe degradation, with hotspots concentrated in the western and southern regions [10, 11]. Western Kenya is one of the most densely populated and impoverished regions in Kenya, with a population density rising to over 1046 people per KM2 in Vihiga County which is above the national Kenyan average of 66 persons per Km2 [12]. The region is characterized by low agricultural productivity coupled, with limited off-farm income options and with more than 58% of households living in absolute poverty [13].

In the past, Western Kenya's traditional land management was based on fallowing unproductive fields in order to restore soil fertility [14]. However, due to the high density of the rural population and land fragmentation, this practice is no longer sustainable. As a result, more people are looking for new land to farm, and they are moving into steep slopes and to other fragile agro ecosystems such as wetlands and adjacent forests all contributing to the increased rates of soil erosion, landslides, soil nutrient loss, soil acidity and physical degradation with the consequences of low productivity in the region [15].

The rate of landscape degradation is increasing at a rapid rate, with soils lost on average 0.5 t ha−1 year−1 in 2017 compared to 0.3 t ha−1 yr.−1 in 1995 [16]. Physical mechanisms of soil degradation prevalent in the region include erosion by water; compaction; hard setting; surface sealing; crusting; and degradation of soil structure [14]. The leading chemical processes include soil nutrient loss; soil organic matter loss; soil acidification; and dominant biotic processes such as pest infestations; changes in vegetation cover and composition (loss of habitat); changes in pollinator population and composition; and changes in soil biota [17, 18].

Nutrient mining is widespread on many smallholder farms in western Kenya, due to continuous cultivation, insufficient nutrient supplementation in relation to plant requirements, and high levels of land erosion, leaching, and removal of crop residue from the fields [19]. Fertile land that used to yield 2–4 t ha−1 cereal grains has become degraded, with cereal crop yields falling to less than one t ha−1 [20]. Although Western Kenya has good climatic conditions and high agricultural potential, the yields of the staple food crops; maize and beans have remained low, with an average of 1 ton of grain per hectare (1 t ha−1) for maize and 2–5 t h−1 for beans with optimal land management

*Protection and Rehabilitation of Degraded Soils in Western Kenya: Experiences from Two… DOI: http://dx.doi.org/10.5772/intechopen.113977*

[1, 21]. Approximately 20 kg of NPK, 4 kg and 20.3 kg of S are extracted from the soil every season, without replacement, for every ton of corn grain produced [22].

Given the above scenario, further land degradation through poor land management should be avoided and, where degradation is already taking place, concerted action should be taken to stop and reverse it. This would help to accelerate the process towards a land degradation neutral future and the achievement of the 2030 Agenda for Sustainable Development (AFSD). The work reported in this chapter was largely based on "conservation and rehabilitation of degraded soils in western Kenya – ProSoil".
