Relationships of random roughness and soil depression storage on coffee farms of varying shade levels

Water availability in rainfed coffee agroecosystems is an important factor in determining the production success of the crop. In this study, an estimate of soil water capture and storage was conducted in order to understand the differences of soil water availability among coffee farms or various management intensities, distinguished here by differences in shade cover level. Measurements of effective soil depression storage were obtained using a roughness clinometer, and soil moisture measurements were taken using electrical resistance soil probes. These measurements were taken to better understand how different shade coffee systems may gain or lose opportunities to keep water within the system due to contributions of shade. Three sites of varying shade were chosen in the Soconusco region of Chiapas, Mexico. The medium (30-50% cover) shade site was found to be more effective for precipitation capture when compared to the low (10-30% cover) shade site because of a larger value of effective depression storage (t-test, p=0.05) due to increased soil roughness. This conclusion was supported by significantly higher soil moisture measurements in the medium shade site when compared to the low shade site in the dry season (Repeated Measure GLM, p=0.001). The high shade (60-80%) site was found to have a greater slope than the other two sites, yielding smaller effective storage capacities, yet the high shade site was able to retain 15% of the available rainfall during the dry season through surface storage. Farmers may consider the use of shade trees within coffee farms as a practical method toward preserving water within the agroecosystem.