Impact of soil conservation measures on the properties and productivity of volcanic soils on the slopes of mount Meru, Arusha, Tanzania.
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Date
2001
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Publisher
Sokoine University of Agriculture
Abstract
A study was conducted to examine the effect of soil conservation measures on soil properties and productivity of volcanic soils on the slopes of Mount Meru, Arusha Region. The experiment was conducted on 27 plots in two agroecological zones namely: medium (1,400-metres above sea level (m.a.s.l.) and high (1,700 m.a.s.l.) altitude zones. Two commonly used soil conservation measures, Fanya Juu and Contour bunds, were tested against non-conserved plots. The effect of soil conservation measures on soil properties was examined by collecting and analyzing soil samples from all treatments. The effect of soil conservation measures on soil productivity was assessed by planting common beans (Phaseolus vulgaris var. Lyamungo 85) as the test crop. Soil conservation measures had no significant effect on the surface soil chemical properties namely: pH, CEC, exchangeable bases, total nitrogen, available phosphorous and organic matter. The depth of Ap horizon in the conserved plots was not significantly different from one another (P=0.05). However,
unconserved plots registered the lowest topsoil depth and they were significantly different from conserved plots. Bean yield differed significantly (P=0.05) due to the effect of soil conservation measures. There was no interaction (P=0.05) between conservation treatments and their respective position in the agroecological zone.Mean bean yield ranged from 0.789 Mg ha'1 in unconserved to 1.367 Mg ha'1 in Fanya Juu terraced plots. Fanya Juu treatments significantly out-yielded (P=0.05)
Contour bund plots by 0.127 Mg ha'1. A similar trend was observed for dry matter yield. Dry matter yield differed significantly (P=0.05) due to treatment effect. Fanya Juu terracing resulted in two folds grain yield compared to control. The highest dry matter yield was registered in Fanya Juu plots, followed by that from Contour bunplots while unconserved plots produced the lowest yield. Mutiple regression analysis showed that depth of topsoil (Ap-horizon) significantly affected bean yield (P=0.01, r=0.64). Depth of topsoil and surface available phosphorous were regressed against
bean yield and it was found that the thickness of the Ap horizon had higher impact on bean yield compared to surface available phosphorous (P=0.01 and R=0.78). Soil moisture profile (0-90 cm) in conserved plots differed significantly (P=0.05) from that in unconserved plots. Conserved plots had higher profile moisture content throughout the growing season. However, soil moisture profile did not differ significantly (P=0.05) between Fanya Juu and Contour bund plots. This suggests that
the two conservation measures have similar effect on soil water conservation. The results from this study confirm the importance of soil conservation measures on Ap horizon development, water holding capacity and crop yield.
Description
Dissertation
Keywords
Soil productivity, Soil compaction, Soil porosity, Soil organic matte, Soil structure