Rating Land Qualities in Grazing Areas: A Case Study of Greyzems in South West Kenya
Loading...
Date
2003
Authors
Wamicha, W. N.
Journal Title
Journal ISSN
Volume Title
Publisher
Soil Science Society of East Africa
Abstract
The criteria for rating soil fertility in grazing areas is not well elaborated. This is because, the
levels of pasture nutrients are wholly dependent on the; minerals to weather, organic matter to
decompose, and on these two processes to release the nutrients and the soil colloids to retain
those nutrients. Hence a soil fertility capability evaluation, based on the ability of the soil
colloids to retain the nutrients was therefore considered to be more appropriate. Soil fertility
capability is dependent on how soils retain plant nutrients. For this reason therefore, two major
plant nutrients (pK)':'Vere correlated with the soil colloids; organic matter, oxides and clay
minerals. The two plant nutrients were found to have moderate to high correlations with the
oxalate extractable oxides (Mn%, Fe%), kaolinite and illite. That is, r=O.62, 0.56, 0.67 and 0.68
with K and r=O.84, 0.39, 0.81 and 0.80 with P respectively. A rating system was then developed
combining; CEC, base saturation and % C as recommended by FAO guidelines together with
oxalate extractable oxides (Mn%, Fe%) and illite to kaolinite ratios as identified in this study. For heoxides an easier criteria of using colour hues was also tested. The Greyzem classification
unitswere finally classified into three soil fertility capability' groups as follows; moderate
(Gleyie), low (Vertic, Haplic) and very low (Lithic). This capability classification also reflects
The stage of weathering whereby the G1eyic Greyzems are the least weathered while the Lithic
Greyzems are the shallowest and relatively the highly weathered. The Greyzems are therefore,
Generally low in terms of soil fertility capability. Soil management in the study area should
Therefore aim at raising this soil property. Of the five rating criteria used, only the organic matter can be managed with reasonable ease in order to elevate the soil plant nutrients retention
capability. Therefore measures aimed at conserving the organic matter should be taken, for
example, by avoiding overgrazing and grass burning.
Description
This paper was presented at the 18th conference and end of millennium celebration of the Soil Science of East Africa (SSSEA) on 'Sustainable use of land resources to alleviate poverty in the new millennium' 4th – 8th December, 2000 held at Mombasa, Kenya
Keywords
Greyzems, Soil fertility capability, Rating system, Extensive grazing land utilization type (LUT).
Citation
18th conference and end of millennium celebration of the Soil Science of East Africa (SSSEA) 4th – 8th December, 2000