Infiltration and soil water repellency in Theobroma cacao plantations:
Stand and Seasonal effects
Abstract
Our understanding of the hydrological processes in cocoa agroforests is
extremely limited. Most work has focused on characterising throughfall
and transpiration processes under various management approaches and
climate change scenarios. However, little is currently understood about
the soil hydrological processes which serve as a link to throughfall and
transpiration. We monitored the soil properties, soil water repellency
and hydraulic conductivity in a 5, 12 and >30 year old
cocoa plantation in the wet and dry seasons. During the wet season
repellent conditions were absent in all stands while the hydraulic
conductivity showed no significant differences among them. This suggests
that stand age has little effect on water movement during the wet
period. During the dry season, the soil at the 5 and 12 year old stands
became extremely repellent and was twice as severe as that of the
>30 year old plantation. It was expected that the extreme
repellency in the younger stands would reduce infiltration rates;
however, higher rates were recorded in the 5 and 12 year old stands.
This was likely due to the combination of a repellent soil matrix and
the presence of large, deep soil cracks which enhanced preferential
flow. As the repellency was not significantly correlated with soil
properties, we hypothesised that the high grass/sedge cover and
temperatures in the 5 and 12 year old stands enhanced it. While further
research is needed to investigate the role that grass and sedges play in
developing repellent conditions, managing their cover may prove
beneficial for the growth and survival of young cocoa trees.