Assessment of Soil Fertility Status and Integrated Soil Fertility Management in Ghana

Abstract

The total land area of Ghana is 23,853,900 ha of which 57.1% (13,628,179 ha) is suitable for agriculture but most of the soils are of low inherent fertility. The coarse nature of the soils has an impact on their physical properties and water stress is common during the growing season. Extensive areas of country’s land area particularly the Interior savannah zone have suffered from severe soil erosion and land degradation in various forms. The soil nutrient depletion rates in Ghana is projected as 35 kg N, 4 kg P and 20 kg K ha⁻¹. The extent of nutrient depletion is widespread in all the agro-ecological zones with nitrogen and phosphorus being the most deficient nutrients. Nutrients removed from the soils by crop harvest have not been replaced through the use of corresponding amounts of plant nutrients in the form of organic and inorganic fertilizers. There is therefore a steady decline in crop yield levels and increased food production is presently due mostly to extension in the area under cultivation. Overall percentage increase in cultivated area between 2000 and 2008 is about 17.3% (SRID 2008). The average yields of most of the crops are 20–60% below their achievable yields, indicating that there is significant potential for improvement While Ghana has one of the highest soil nutrient depletion rates in SSA, it has one of the lowest rates of annual inorganic fertilizer application – only 8 kg per hectare.

An increase in food security requires increased productivity strategies that will raise yields for most crops toward their achievable levels, mostly by the adoption of intensive and improved technologies, including the use of fertilizers, improved seeds and best management practices. While African policy makers and International donors recognize the urgency of raising fertilizer use by small holder farmers, for achieving both agricultural growth and poverty alleviation objectives, there is little consensus on the most appropriate policy and programmatic course of action. Most efforts to raise fertilizer use in SSA over the past decade have focused on fertilizer subsidies and targeted credit programmes with hopes that these programmes could later be withdrawn once the profitability of fertilizer use has been made clear to newly adopted farmers and once they have become sufficiently capitalized to be able to afford fertilizer with their own working capital. Relatively little emphasis has been given to improving the profitability of fertilizer use through understanding the most productive levels and combinations of nutrient input for various agro ecological areas, management practices and market options. Inorganic fertilizer does not improve agricultural productivity in isolation. Information on the fertility status and agricultural potential of the soils are also required. Complementary inputs such investment in soil and water conservation for efficient end optimal nutrient uptake is also important. Improved soil fertility management through increased levels of fertilizer use, increased use of available organic soil amendments, and improved farm management practices, together with the use of improved seed, can result in positive gains in farm productivity. This increase in productivity is demonstrated by the SAWA technology in rice production where yield on farmers’ fields increased from 1 ton/ha to 5 tons/ha (Buri et al. 2007). There is lack of information on the profitability of the different soil-crop-fertilizer combinations that could be employed in the different parts of the country. The lack of such information on crop-fertilizer profitability across the country means that farmers cannot tell how much they stand to gain or lose by applying a particular type of fertilizer on a particular crop. This increases their risk and creates a disincentive for use of fertilizer. Information about profitability levels can serve as an incentive for inorganic fertilizer use. Most simply, expected Value Cost Ratios (VCR) from fertilizer use can guide farmers’ decisions. Knowledge of soil characteristics and processes regulating nutrient availability and supply to crops is essential to raise productivity per unit of fertilizer nutrient applied. The recommendation of the African Fertilizer Summit (2006) to increase fertilizer use from 8 to 50 Kg/ha nutrients by 2015 reinforces the importance of fertilizer for increasing crop productivity and attaining food security and rural wellbeing in Ghana. The impact of this target will however vary depending upon the agronomic efficiency of applied fertilizer. This efficiency varies across ecological zones, farms and fields within farms and greatly affects the returns to the recommended 50 Kg/ha. The application of insufficient fertilizers and inappropriate nutrient conservation practices by farmers contribute to accelerating the rapid decline in soil fertility. The efficient uses of both inorganic and organic fertilizers, through Integrated Nutrient Management approach, will form an important element of a holistic approach for sustainably increasing crop production in Ghana.