Abstract
In most developing countries including Nigeria, fertilizers are applied to the soil by uneducated farmers without particularly making reference to the specific need of the plant or soil. Therefore, intended efficiency/replenishment is not maximized and fertilizer use is not rationalized. This paper critically reviews the three basic approaches to soil fertility evaluation: Visual symptoms of nutrient deficiency, Plant tissue analysis and soil testing. The implications of these methods are examined in terms of predicting fertilizer requirements for crops in Nigeria. Furthermore, the paper discusses the methods of Soil fertility evaluation available. Focus is then shifted primarily to the soil testing method, describing in detail the main objectives behind carrying out soil testing, including the proper soil sampling tools, sound sampling techniques and handling of the samples. Key words: Soil fertility evaluation, fertilizer, soil sampling, Nigeria.
Highlights
Soil, being the natural medium for plant growth has a direct impact on yield and quality of crops growing on it
In most developing countries including Nigeria, fertilizers are applied to the soil by uneducated farmers without making reference to the specific need of the plant or soil
This paper critically reviews the three basic approaches to soil fertility evaluation: Visual symptoms of nutrient deficiency, Plant tissue analysis and soil testing. The implications of these methods are examined in terms of predicting fertilizer requirements for crops in Nigeria
Summary
Soil, being the natural medium for plant growth has a direct impact on yield and quality of crops growing on it. Low fertility of Nigerian soils is the major constraint in achieving high productivity goals. In both rain-fed and irrigated systems, nutrient replenishment through fertilizers and manures remains far below the crop removal, causing mining of native reserves over the years. Soil fertility evaluation is the process of estimating the amount of native and residual nutrient elements which could be available for use by growing crops in particular soil and the amount of fertilizer to be supplemented for profitable crop production (Sanchez et al, 1997). Soil fertility evaluation is a powerful tool to support high productivity by way of rationalizing nutrient use, its current impact on farm practice is presently not visible. In order to make it an effective and farmer oriented service, it is imperative to (1) Expand the arena of soil fertility evaluation beyond NPK, and as well as the pH of the soil. (2) Develop fertilizer recommendations for high yield targets, involving all deficient nutrients and exploiting important positive nutrient interactions
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