Characteristics of water balance in a rainfed paddy field in Northeast Thailand

Abstract

Rice productivity in rainfed paddy fields varies with seasonal changes of water availability in which the conditions of flooding are affected by the water balance. Hydrometeorological measurements were performed in a rainfed paddy field in Northeast Thailand from July 2004 to December 2006 to analyze the water balance. As a result of our measurements, climatologically conditions were classified as semi-humid with an annual precipitation of 1,100 mm/year and annual potential evaporation of 1,660 mm/year in both the year. The surface layer of the paddy soil was clayey and the hydraulic conductivity was very low, so groundwater levels remained below the soil surface even under flooded conditions during the rainy season. Seasonal changes in the amount of soil water were very small, comprising only less than 16% of the total precipitation during the rainy season. Consequently, an effective precipitation of less than 180 mm was enough to establish standing water in the rainfed paddy field.

Modeling the dependence of the crop calendar for rain-fed rice on precipitation in Northeast Thailand

“…This is in agreement with many previous field surveys, which reported that transplanting dates varied widely even within a small watershed (Miyagawa et al 1999;Homma et al 2001). Even where only limited rainfall is available, a certain portion of the paddy field can collect ponding water because of its lower elevation or lower permeability of the soil to water (Tsubo et al 2007;Goto et al 2008). In these situations, paddy fields will be established earlier where ponding water can be obtained easily and later where water availability is lower.…”

Irrigation water productivity in Cambodian rice systems

“…It is clear from the studies listed that a focus on water use as quantified by different measures of evapotranspiration (actual, as in Bastiaanssen and Zwart, ; potential, as in Goto et al., ; and reference, as in Allen et al., ) dominates the existing knowledge. However, only a small part of this literature considers the lower Mekong basin, and an even smaller part considers Cambodia.…”

Effect of Paclobutrazol Application Time on Growth, Yield and Starch Content of Two Cassava Cultivars under Rainfed Conditions of Northeastern, Thailand

“…Northeastern Thailand has a semi-humid tropical climate which is characterized by rainy (May-October) and dry (November-April) season (Goto et al 2008). Cassava is a cash crop of smallholder farmers in northeastern Thailand.…”