Soil fertility decline is one of the acute problems facing farmers in the world and Nigeria in
particular. The constraints to food security and widespread poverty, as they affect
development and livelihoods, are well known even in Sub-Saharan region of Africa (SSA),
where population growth at 3% supersedes agricultural production rate of 2% per annum
(Bationo et. al, 2006). Although the causes of food insecurity and poverty are numerous, the
decline in soil fertility with resultant decreasing crop yields is severally highlighted and
stressed (Sanchez et. al, 1997; Smaling et. al, 1997; Bationo et. al, 2006).
In Nigeria, the practice of shifting cultivation which was one of the effective methods of
overcoming the problem of poor crop yield due to decline in soil fertility has virtually
disappeared. This could be linked to the increasing population explosion and the stiff
competition for land space by other land uses (Hati et. al, 2005). According to Ayoub (1994),
population explosion added to the increased continuous farming on the available land by
farmers who often do not add adequate soil nutrient supplements (organic and inorganic
fertilizers) to beef up soil fertility and increase yield.
Makinde et. al, (2001) reviewed that decline in soil fertility is a fundamental impediment to
agricultural growth and food production. According to them, crop production in the past relied
on shifting cultivation to maintain the fertility and productivity of the soil through organic
matter build up during a long fallow period. This practice enabled farmers to produce
substantial crop yield over a period even without adding external inputs. Okalebo et. al,
(2009) observed that decreases in available nitrogen and phosphorous are among the most
severe nutrient problems in the tropics.