Morphological adaptation of cocoa fine roots under shaded of langsat tree in exploring stony soil

Abstract

Abstract Cocoa fine roots are responsive to changes in the soil environment to maximize nutrient and water absorption for plant growth. The presence of rock increases soil density and decreases available water content, promoting modification of fine root development. The purpose of this study was to clarify the effect of the physical properties of stony soil on the morphological properties of fine roots. In three land-use systems, soil samples were taken from four depths using a sample core measuring 385 cm3 in three land-use systems. Fine roots were extracted by the immersion method, to measure the length of fine roots from five classes of orders based on diameter. We notes, the bulk density of stony soil increases as the rock mass increases, and the depth increases. The available water content decreases with the increase in bulk density, and this decrease is more pronounced in the lower soil layer. Fine root length was found more in the lower order diameter class, decreasing soil moisture against the bulk density gradient. The bulk density in the topsoil layer reaches 1.71 g cm-3, increasing to 1.84 g cm-3 in the lower soil layer. It seems unreasonable, when compared to the general density of soil mass. Still, this result is solely due to the high fraction of rock with a higher density. Fine roots were dominated by orders 1 and 2 with root diameters < 0.25 mm and < 0.50 mm, reaching 70% of the total fine root length. Fine roots in this diameter class act as absorbent roots, acquiring water and nutrients from the soil.