Researchers studied soil moisture across six land-use systems in Bolivia. These included cocoa monocultures, agroforestry systems, both under organic and conventional management, a successional agroforestry system, and a natural fallow. They measured soil moisture down to 70 cm over 18 months.
Soil texture varied widely across the trial area. Researchers identified two distinct soil groups. These groups differed in clay content, bulk density, and water retention capacity. This variation existed even within a small area.
Land-use system shaped how soil moisture changed with depth. In monocultures, moisture dropped mainly in the topsoil during the dry season. Deeper layers stayed moist year-round. In agroforestry systems, moisture dropped more evenly across the whole soil profile.
This pattern points to complementary water use. Cocoa roots draw from shallow soil. Shade tree roots draw from deeper layers. The two root systems don’t appear to compete for the same water.
Shade also protected topsoil moisture. The uppermost soil layer held more moisture in agroforestry systems than in monocultures. Shade trees reduced water loss through evaporation and reduced cocoa transpiration.
Cover crops made no measurable difference. Soil moisture in organic monocultures, which used a legume cover crop, did not differ from conventional monocultures with bare soil.
Soil type affected water availability but not yield. One soil group held less available water than the other throughout the study. Still, researchers found no effect on cocoa bean production.
