Abstract
This analysis compared the suitability of contiguous fallow-forest lands for cassava, yam, cocoyam and sweet potato production in Nsukka, south-eastern Nigeria. The fallow plots were brought into cultivation in 1998 under the IITA-UNN long-term collaborative research. The sole cassava plots were grown to cassava only continuously for five years and then left to fallow. Soil samples were collected from 0-20 cm depth in triplicates using an auger and core sampler from the seven representative fallow plots previously grown to sole cassava from 1998–2003 and under fallow till date as well as the adjacent forest land. The objective was to use the soil qualities as recovered during the fallow period and those from the original adjacent forest to determine their current suitability for the production of the four crops. Using the FAO’s principle of limiting conditions revealed that after 13 yrs of fallow, the plots grown to sole cassava was classified as highly suitable (S1) for sweet potato production but moderately suitable (S2) for cassava, yam and cocoyam production. The remnant forest land was highly suitable for sweet potato production but moderately suitable for cassava, yam and cocoyam production. The dominant soil limitations are organic matter, low cation exchange capacity and exchangeable potassium for both cassava and yam production. The major limitations to cocoyam production are low available phosphorous, base saturation and soil pH. If these constraints are addressed adequately by soil nutrient management programmes all the plots will scale up to S1 class for the four crops.
Highlights
Soil fertility depletion is a major problem in tropical Africa, resulting to decline in per capital food production as crop lands have a negative nutrient balance, due to crop harvest, leaching and low inputs applied to the soil [1, 2,]
Food crops grown on millions of hectares of soils all over the tropics no longer perform optimally well because most of the soils do not contain enough essential nutrients resulting in poor yields and subsequently the starvation of the people [41]
It lies within the latitude 6o 52 ́ N and longitude 7o 23 ́ E in the Savannah zone of Southeastern Nigeria with an elevation of 447.2 m above sea level [43]
Summary
Soil fertility depletion is a major problem in tropical Africa, resulting to decline in per capital food production as crop lands have a negative nutrient balance, due to crop harvest, leaching and low inputs applied to the soil [1, 2,]. Food crops grown on millions of hectares of soils all over the tropics no longer perform optimally well because most of the soils do not contain enough essential nutrients resulting in poor yields and subsequently the starvation of the people [41]. These yield reductions are mostly due to nutrient deficiencies resulting from decreases in soil organic matter content [42] and depletion of soil nutrients reserve during the cropping season. Growing a crop on a land without due assessment of its suitability for such use, leads to suboptimal soil productivity and low yield as crop requirements are not often related to the land’s potential capacity [26]
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