Working Document Series Open Access 2012 RUF-32750

Speargrass as a Soil Fertility Indicator along a Deforestation Chronosquence

A.K. AmodingM. Karuhanga-BerahoS. KiconcoK. SenkosiJ.S. Tenywa

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Abstract

171 words

This study estimated the time taken for speargrass (Imperata cylindrica) to occur on arable fields along a deforestation chronosquence; established the effect of burning on soil properties and determined the reliability of speargrass as a soil fertility indicator. Results showed that speargrass never grew in the study fields within the first six years of cultivation. During the same period average values for bulk density, total N, K, organic matter and soil pH were within the recommended ranges for optimal crop growth. After six years of cultivation in burnt and un-burnt fields on both Nitisols and Red Latosols, average values of the above parameters decreased below their critical levels and continued to deviate negatively from the critical range by years of cultivation. During the same period, speargrass infestation set-in and shoot count rose with time. Speargrass populations rose faster in fields with lower total N, K and organic matter and higher bulk density. This confirms that speargrass infestation and subsequent invasion is favoured by declining soil fertility thus, indicative of soil degradation.

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