Physical rice grain quality as affected by biophysical factors and pre-harvest practices

Varietal purity and proportions of grains with brown spots, fissured grains, chalky grains andwhole grains in a rice sample are important grain quality attributes influencing consumers preference and price but little information exist on how these grain quality attributes are affectedby biophysical factors and pre-harvest practices. Several authors have studied in isolation theeffect of biophysical factors and pre-harvest practices on rice grain quality but most of thesestudies neither looked at these within the context of agro-ecological zones nor productionsystems. The effects of agro-ecological zone (AEZ) (highlands, sub-humid, humid andsemi-arid), production system (irrigated lowland, rain-fed lowland and rain-fed upland) andpre-harvest practices on grain quality attributes were investigated in 5 African countries usingdata collected through on-farm survey. The rice samples were generally characterized by lowvarietal purity, high proportion of brown spots, fissured and chalky grains and a low proportionof whole grains. Also, they had large variations across and within AEZs and productionsystems. AEZs and crop establishment method affected varietal purity. AEZ, production systemaffected chalkiness. AEZ and type of variety influenced percentage of grains with fissures.Percentage of whole grains were affected by AEZ, production system and weeding frequency.While grain quality attributes were strongly affected by biophysical factors, there is also roomfor improving grain quality through good pre-harvest practices.

Keywords:

Agro-ecological zone , Oryza spp , Production systems , Varietal purity , Brown spot , Chalkiness , Fissures , Whole grains , Africa