Effects of introduction of combine harvester and flatbed dryer on milling quality of three glutinous rice varieties in Lao PDR

Abstract

ABSTRACTMechanization is required to increase labour productivity and improve grain quality for rainfed lowland rice in Lao PDR and neighbouring countries. An experiment was conducted in dry season in 2016 with three rice varieties and also in wet season in 2017 with two varieties to investigate the effect of introduction of combine harvester and flatbed dryer on milling quality of glutinous rice. The treatments were different harvest methods (hand and combine harvester), drying methods (sun and forced air drying with flatbed dryer) and storage period up to 6 months. Head rice yield (HRY) improved greatly with forced air drying with mean HRY of 46.1% compared to 28.8% in sun drying. Milling quality of grain harvested by combine was similar to that of hand-harvested crop. The results also revealed large difference in HRY between varieties; mean HRY across two seasons was 40.1% and 27.1% for Thadokkham (TDK8) and TDK11, respectively. These treatment effects and also their interactions on HRY were strongly related to the proportion of broken rice. HRY declined from 39.4% to 35.4% with 4-month storage, but there was no further reduction with 6-month storage. This study showed that the milling quality of glutinous rice improved greatly with the introduction of flatbed dryer but only little with combine harvester. Milling quality also varied greatly among varieties and slightly with storage period. Further study is required to investigate physiological and morphological characteristics of varieties and postharvest methods that determine the milling quality of rainfed lowland rice.Abbreviations: HRY: head rice yield; BR: brown rice; MR: milled rice; MC: grain moisture content; TDK: Thadokkham; WS: wet season; DAP: days after planting; RRC: Rice Research Center; H: harvest; D: drying; S: storage