First use of the 137Cs technique in Nigeria for estimating medium-term soil redistribution rates on cultivated farmland
Loading...
Date
2010
Journal Title
Journal ISSN
Volume Title
Publisher
Soil & Tillage Research
Abstract
Soil erosion is a serious problem in the forest-savanna transition zone or derived savanna of West Africa
and Nigeria and needs to be reduced to maintain soil quality and to ensure food security. In 2007, the use
of the fallout radionuclide 137Cs as a tracer for estimating themagnitude of medium-term (40–50 years)
rates of soil redistribution was tested at a research station in Ibadan, Nigeria, to investigate, for the first
time, its applicability in the derived savanna of West Africa.
Because of the traditional tillage practice for cassava cultivation of creating downslope oriented
ridges and furrows during the annual ploughing, there was a need to adapt the 137Cs approach to these
specific condition. The mean inventory was determined for cores collected from both ridges and furrows
at different positions down the slope and this value was used to estimate the downslope variation in the
longer term soil redistribution rate. The mean 137Cs reference inventory obtained for an undisturbed site
was 568 138 Bq m 2. The average inventory for the upper slope of the cassava field (423 323 Bq m 2)
was generally lower than the average inventory for the middle slope (509 166 Bq m 2) and for the lower
slope (606 245 Bq m 2) and these results provided clear evidence of the downslope movement of soil. The
mean 137Cs inventory for the study area within the cassava field (496 273 Bq m 2) was 13% lower than the
reference inventory, indicating that some of the soil mobilised and redistributed by erosion had been
exported beyond the field.
Using 137Cs data set and the conversion model mass balance model 2 (MBM2), the gross erosion rate
from the cultivated site was estimated to be 18.3 t ha 1 year 1 and the net erosion rate
14.4 t ha 1 year 1, providing a sediment delivery ratio of 78%. These estimates are comparable to the
rates generated by conventional soil loss measurements made close to the study site. The study
demonstrates that the 137Cs technique can be successfully used to obtain data on medium-term soil
redistribution in the derived savanna of Nigeria, and that it could be a useful tool for supporting the
improvement of soil conservation on farmland in West Africa.
Description
An article published by Soil & Tillage Research 110 (2010) 211–220
Keywords
NIgeria, Soil erosion, Cultivated land, Radionuclide technique, 137Cs, Sediment delivery
Citation
Soil & Tillage Research 110 (2010) 211–220