effect of some soil fertility management options on the growth and yield of soybean and maize varieties in SOUTHEASTERN NIGERIA
There is a growing concern all over the continent of Africa over the decline in the productive
capacity of the continent’s soil resources due mostly to declining soil fertility with cultivation.
Agricultural productivity is reported to have actually declined over the past 45 years in many
African countries which has been blamed on soil degradation as its major cause (Bluffstone and
Köhlin, 2011). Sanchez (1987) had earlier observed that soil fertility depletion is the
fundamental cause of low per capita food production among smallholder farmers in Africa who
remove huge amounts of nutrients from the soil without returning any at the rate of 22 kg N, 2.5
kg P and 15 kg K per hectare over the past 30 years in 37 African countries (Anon, 2003).
However, reports show that where farmers applied fertilizers at all, very little are used as low as
less than 20 kg/ha which is strikingly low compared with the 200 kg/ha common in European
agriculture (Tittonell et al., 2008). “African Green Revolution” in which fertilizer use is expected
to rise from 8 kg/ha to at least 50 kg/ha annually by 2015, was launched in Abuja, Nigeria to
indicate the need for increased fertilizer use in Africa, known as “Abuja declaration 2006”.
Almost all agricultural intensification to guarantee food security for all, hinges on heavy use of
fertilizers (ENDA, 1977), but the tropical soils do not respond well to some of the temperate
farming practices involving the use of fertilizers, herbicides and pesticides (Houngnandan et al.,
There is a strong nexus between soil fertility management and demographic growth rate
especially in Africa where food production is lagging behind demand for food. Rapid population
growth and urbanization consequently led to increased demand for land especially for cultivation
of food crops to avert hunger. The consequent severe pressure on soil productivity made most
soils lose their fertility quickly (Kang et al., 1984, Kang and Reynolds, 1986, Spore, 2009). The
more the population the more access to good agricultural land is restricted in regions where land
area per capita is continually decreasing, yet it is these regions where the demand for agricultural
products is continually rising (Spore, 1994) and consequently requiring land use intensification.
Soil study and fertility interpretations of the Southeastern Nigeria….