Characteristics of Plough Pan under Cassava Production Areas in Nakhon Ratchsima Province

Abstract

A study on plough pan in cassava production areas of Nakhon Ratchsima province was carried out inthree soil series, namely Warin, Yasothon and Satuk soil series, aiming at investigating characteristics of plough panalong toposequences and its limitation on growing cassava. Result showed that soils were mostly in sandy texturegroup dominated by fine and very fine sand particles. Plough pan (Btd) occurred underneath topsoil (Ap) andoverlaid argillic horizon (Bt), starting at a depth between 15-25 cm with 13-32 cm thick. There was no relationshipbetween starting depth and thickness of plough pan with position in the landscapes. Bulk density of plough pans wasmostly greater than 1.6 Mg/m3 with those found in Yasothon soil having the highest average value of 1.83 Mg/m3. All plough pans had greater bulk density than did topsoil and subsoil layers directly overlying and underneath.Hardness of plough pans ranged between 0.34-5.23 kg/cm2. Saturated hydraulic conductivity of these pans, havingclose relationship with bulk density, varied between 0.2-3.4 cm/hr with Satuk soil having lower average value thanthat of the rest due to its parent material which derived from siltstone, causing the soil to have smaller pore size.Available water capacity of plough pan of 5.34% by volume in Warin soil was found the highest compared to 4.12and 3.97% by volume of Satuk and Yasothon soils, respectively. Properties of studied plough pan such as high bulkdensity and hard when dry which restrict cassava root penetration, low saturated hydraulic conductivity whichimpedes vertical water flow and result in the accumulation of water runoff and subsequent erosion, and low availablewater capacity which limits water use of cassava during drought period, all have negative impact on cassava growthin this production area.