Agriculture Reference
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complete block under two fertilizer regimes (F1 = 18 kg N and 46 kg Pe 2 O 5 and
23 kg N ha −1 at tillering; F0 = without application of fertilizer) with three replica-
tions. The fertilizer levels considered here reflect conditions in Ethiopia (Assefa and
L e d i n 20 01).
Significantly higher average dry matter forage yields of mixtures, pure oats, and
pure vetch were obtained on the red Nitosol (9.7, 9.4, and 4.5 tons/ha, respectively)
than on the black Vertisol (5.6, 5.5, and 2.8 tons/ha, respectively). The example illus-
trates differences in yield for two different soil types that have a similar soil reaction
(pH [1:1 H 2 O] of 4.6-5.0), organic carbon content (1.8%-2.5%), and % clay (51%-65%)
in the study area, yet with markedly different clay mineralogy. The reported experi-
ments were made under controlled conditions, which are likely to differ on farms in
the area. Be that as it may, crop yields on the Nitosols are above subsistence level
and provided that the amount of fertilizer can again be applied every year, ecosystem
service 1 (biomass production) is marginally assured, providing a certain degree of
soil security. The picture is different for the Vertisol, for which production levels
were approximately 40% lower, leading to lower soil security.
2.3.3 f erralSolS in m oZamBique
Materechera and Mkhabela (2001) reported changes in the properties of strongly
weathered Ferralsols under conditions of low external input farming systems associ-
ated with differences in land use and management practices. Their study was con-
ducted on a small farm at Malindza, Swaziland. The area falls under the eastern part
of the low veld (“bushveld”). The 5-ha farm is on a gently undulating terrain at an
altitude of about 700 m. The climate is subtropical with a mean annual rainfall of
760 mm (range, 650-1050 mm). For over a decade before 1987, the whole farm was
under natural vegetation and used for grazing by about 100 head of cattle. A kraal
and holding pen for handling the animals was located on a 0.5-ha piece of land in the
center of the farm next to the homestead. In 1987, all animals were removed from
the farm and crop production was introduced. Three treatments were compared:
(i) “kraal” areas where before 1987 the cattle used to stay during the night had the
highest maize yields, followed by (ii) fallow fields after clearing and (iii) by continu-
ous maize. The latter two had negative nutrient balances and yields below subsistence
levels. If former “kraal” areas are not fertilized, they are bound to degrade in time.
2.3.4 n itoSolS , f erralSolS , and a criSolS in w eStern K enya
The highlands of western Kenya support one of the densest rural populations in the
world, with >1500 inhabitants/km 2 in the Vihiga district with fertile soils. Population
growth, however, has gradually led to depletion of nutrients through crop harvest
removal, leaching, and soil erosion. Farmers have largely been unable to compensate
such losses via crop residues, manure, and mineral fertilizers (Shepherd and Soule
1998), adversely affecting ecosystem services and soil security. The observed pat-
terns of soil deterioration are spatially heterogeneous in the area. Spatial and tempo-
ral niches for targeting soil fertility management and technologies were studied by
Tittonnell et al. (2005). The dominant soil types are Humic Ferralsols, Dystric and
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