Elsevier

Geoderma Regional

Volume 13, June 2018, Pages 43-51
Geoderma Regional

Knowledge and management of soil fertility by farmers in western Cameroon

https://doi.org/10.1016/j.geodrs.2018.02.001Get rights and content

Highlights

  • Farmers around Mount Kupe use at least seven indicators to identify fertile soils.

  • The dominant technique for soil fertility management is minimum tillage.

  • Different management practices lead to different degrees of soil deterioration.

  • Site specific soil fertility investigations and nutrient management are essential.

Abstract

This study was conducted to assess farmers' perceptions of soil fertility, identify major soil fertility management (SFM) practices and to evaluate the effects of dominant SFM practices on soil quality. Field data were obtained using semi-structured questionnaires in seven localities: Nyassosso, Mbabe, Mbule, Nsuke, Ngab, Tombel and Kupe. The impact of dominant SFM practices on soil quality in various land use types was evaluated using the deterioration index (DI). Soil sampling and laboratory analysis were performed following standard procedures. Soil properties considered were bulk density (BD), organic carbon (OC), available P, total N, exchangeable bases (Ca2+, Mg2+, K+) and cation exchange capacity (CEC). Farmers make use of at least seven indicators to differentiate between fertile and infertile soils. Out of 256 farmers surveyed, 91.4% use minimum tillage as a technique for maintaining soil fertility, while 18.8% use chemical fertilizers to improve soil fertility. Compared to reference sites, overall DI values were: +224.4% (Tombel) < +133.7% (Nsuke) < +62.6% (Nyassosso) < −26.0% (Kupe) < −57.8% (Mbule) < −99.6% (Ngab) < −124.9% (Mbabe). The variations in soil attributes observed at the different sites is indicative of the complexity of nutrient dynamics following land use changes, coupled with farmer-specific SFM practices. For effective and sustainable SFM, site specific soil fertility investigations are imperative for efficient management of soil nutrients.

Introduction

Soil fertility decline and reducing crop yields are major global concerns that contribute to acute poverty in developing countries, this as a result of inappropriate soil fertility management practices (Lal, 2015). These concerns are further exacerbated by climate change (Sanchez, 2000; Swaminathan and Kesavan, 2012), where climatic factors keep varying and imposing extreme weather conditions such as droughts, floods, extreme heat waves and increased fire frequency on the environment. Sustainable soil fertility management and crop production are needed to feed >7 billion people in the world. Although methods of soil conservation and soil fertility restoration are well known (Buresh et al., 1997; Manrique, 1993; FAO, 1999; Lal, 1993; Palm et al., 2001; Gurtner et al., 2011; Dumanski and Peiretti, 2013; Lal, 2015), their proper adoption and implementation by farmers in developing countries are constrained by lack of adaptive technology, limited material and financial resources, poor access to farm inputs, increase in population size and pressure on land resources, etc.

The western slopes of mount Kupe, in southwest Cameroon, are endowed with naturally young and fertile volcanic soils, and agriculture is the primary economic activity. Given that soil fertility depends on intrinsic soil properties, management practices can significantly reduce soil quality negatively, reducing or upsetting ecosystem services (Palm et al., 2014), leading to reduction in crop yields. Over the past decades, soils on the slopes of mount Kupe have been intensively used for agricultural production due to increase in population. Most of the farms have been established following destruction of both natural forests and even the encroachment into protected forests. Ecologically, mount Kupe is one of the few areas of the world having montane cloud forests, which serve as home for many endemic plant and animal species, where biodiversity conservation remains an urgent priority (Bowden, 2001).

Other remaining cloud forests in Cameroon include the mount Oku forest reserve in the North West region (extending from 2219 m around Lake Oku to 3011 m on the summit of Mount Oku). The cloud forest in Oku is endowed with very rich endemic plant and animal species, and, is in critical need of conservation action given that it was identified as the only extensive area of tropical montane forest left in the Bamenda Highlands of Cameroon. According to estimates by Macleod (1986), there were about 17,500 ha of cloud forest in the Mount Oku area in 1963. Between 1983 and 1985, agricultural encroachment caused the loss of >1700 ha through agriculture, grazing and burning, and by 1986, about 10,500 ha had been lost and 2700 ha were heavily degraded. As a consequence, the Oku forest was declared a reserve and protected by law in 1987 (Neba, 2006). In the South West region of Cameroon, other cloud forests are found in the mount Cameroon montane forest reserve (ranging from 1600 to 1800 m asl) situated within the mount Cameroon National Park (58,178 ha), the Banyang-Mbo wildlife sanctuary (69,145 ha), the Korup National Park (126,900 ha) and the Bakossi Forest Reserve (29,320 ha), which are biodiversity hotspots in central Africa.

Many studies recount how environments with great agricultural potentials and rich biodiversity have been degraded and have become unproductive due to unsustainable agricultural practices (Hartemink, 2003). Generally, soil degradation is evident from the rapid loss in soil fertility when forest vegetation is converted to farmlands and plantation agro-ecosystems (Hartemink, 2003). Restoration of soil quality for improvement of crop yields is thus a necessity which demands urgent measures such as soil erosion management, soil biodiversity improvement, implementation of soil restorative farming and cropping systems, and smart agricultural intensification which allows for significant gains to be made in terms of soil organic carbon storage, water use efficiency and biodiversity (Lal, 2015; Tadele, 2017; Govers et al., 2017).

Conservation agriculture has been considered as the key to soil fertility maintenance and restoration through retention of crop residue mulch, incorporation of a cover crop in the rotation cycle, use of integrated nutrient management involving combination of chemical and bio fertilizers, and elimination of soil mechanical disturbances (Lal, 2015). With new legislations restricting the clearing of native forests for agricultural purposes, future strategies for increasing agricultural production will have to focus on agricultural intensification by using available natural resources in a more efficient, effective, and sustainable manner.

Generally, soil fertility and nutrient management practices vary from farmer to farmer, even at the local scale (Nkamleu, 2007), due to farmers' knowledge and perceptions of soil fertility and management (Saito et al., 2006; Desbiez et al., 2004; Dawoe et al., 2012), and the diversity and differences in farming systems (Knowler and Bradshaw, 2007). Also, there is usually a knowledge and information gap between researchers and farmers (Vandeplas et al., 2008; Wesseler and Brinkman, 2002), which hinders adoption of soil fertility management recommendations (Lambrecht et al., 2014). Considering soil types and management, local farmers usually possess some competences, usually based on experience, which permit them to detect differences in soil fertility levels within their farms (Saïdou et al., 2004; Buthelezi et al., 2012; Dawoe et al., 2012). Making use of local soil fertility indicators such as crop yields, soil morphological characteristics, weed type, pests, and diseases among others, farmers resort to different management practices with the aim of improving, maintaining, or restoring soil fertility. For example, 62 soil fertility indicators (classified into five categories as follows: those relating to soil characteristics, crop performance, agricultural management, environmental factors, and biology) are used in Nepal (Desbiez et al., 2004), 6 in Gidan district of Ethiopia (Yeshaneh, 2015) and 5 in the savannah zone of Central Cameroon (Ndaka et al., 2015). These differences in farmer perception on soil fertility and management generate soil fertility gradients and management intensity gradients, which lead to variations in crop yields at various spatial scales (farm level or regional scale) (Tittonell et al., 2007). Therefore, information about farmer perceptions on soil fertility and management is necessary for sustaining agro-ecosystems through site-specific management. Unfortunately, information on farmers' perceptions on soil fertility and management is lacking in the Mount Kupe area of Cameroon, a major cocoa producing area in Cameroon. The objective of this study was to assess farmers' perceptions of soil fertility in the western slopes of mount Kupe through the identification of dominant soil fertility management practices used by local farmers, and evaluate changes in selected soil properties following the long term use of dominant soil fertility management practices, to inform on their sustainable management.

Section snippets

Location and biophysical characteristics of the study area

Mount Kupe is located between latitudes 4°43′N and 4°52′N and longitudes 9°38′ E and 9°47′ E, approximately 100 km north of Mount Cameroon. The climate of the area is classified as Af (tropical wet), according to the Köppen classification system, typical of central Africa with two distinct seasons: the rainy season which spans from March to November and the dry season from November to March. Mean annual rainfall is 3095.6 mm (ranging between 1672 and 4139 mm) while mean annual temperature is

Characteristics of farmers and their farms

The characteristics of the farmers surveyed are shown in Table 1. The majority of farmers fell within the age groups from 41 to 50 years followed by those with 51–60 years and 30–40 years, while those with ages below 30 years were the least. These results indicate that younger people are less involved in farming activities compared to the older population.

Generally, many young people migrate to the towns in search for jobs and for educational opportunities. Although most of the households had

Conclusion

The purpose of this study was to identify dominant soil fertility management practices used by farmers in the western slopes of mount Kupe, based on the appreciation of their soil fertility status. Based on an exhaustive survey of farmers' practices, it can be concluded that individual farmers have unique ways of evaluating the qualitative fertility status of soils. Although chemical fertilizers are known to be an integral part of most farming systems in tropical environments, this study

Declarations of interest

None.

Acknowledgements

We are grateful to all farmers who gave their collaboration during field work and especially to those who permitted us to use their farms for soil sampling. Special thanks to Chief Ediage, Stephen Enang, Albert Alobwede and Ngole Ngole for their invaluable assistance in data collection and for providing relevant information. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

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