On-farm evaluation of effectiveness of improved postharvest handling of maize in reducing grain losses, mold infection and aflatoxin contamination in rural Uganda

Abstract

Postharvest losses remain a challenge among smallholder farmers in sub-Saharan Africa. The uses of hermetic storage containers  (hermetic bags and metallic silos), tarpaulin sheet (plastic sheet) and raised racks reduce postharvest deterioration of grain. This study evaluated the effectiveness of selected improved drying and storage postharvest technologies and practices in reducing maize grain postharvest losses among smallholder farmers in Kamuli and Apac districts, Uganda. The assessed improved storage technologies were hermetic bags and metallic silos against woven polypropylene bags (common farmer practice). For drying, use of tarpaulins and raised racks were assessed against drying on bare ground (common farmer practice). Grain quality and quantity were determined at harvest as well as during drying and six months of storage using Longe 10H variety. Mean quantitative losses, mold infection and aflatoxin level of maize at harvest were 13.72 ± 5.44%, 59.01 ± 17.97% and 1.21 ± 0.7 ppb, respectively for traditional practice. Improved drying and storage technologies resulted in significantly lower (p≤0.05) losses, mold infection and aflatoxin level than the common  farmer practices. Drying on bare ground (3.04 ± 1.50%) resulted in 1.94 times and 7.07 times higher quantitative losses than drying on  tarpaulins (1.56 ± 1.09%) and raised racks (0.43 ± 0.58%). By the sixth month of storage, polypropylene bag storage resulted in 3.7 times and 84 times higher quantitative losses (23.7 ± 5.11%) than hermetic bags (6.33 ± 5.41%) and metallic silos (0.28 ± 0.22%), respectively. Polypropylene bag storage also resulted in 4.4 times and 6 times higher aflatoxin levels (45.82 ± 20.88 ppb) than hermetic bags and metallic silos, respectively. The interaction effects of type of drying technology and storage technology used on aflatoxin levels at the end of the storage period was significant. The highest mold infection and aflatoxin levels were observed when drying was done on bare ground and storage was in polypropylene bags and by the sixth month of storage, mold infection was 90.54 ± 5.48% and average aflatoxin content was 53.47 ± 22.79 ppb. Storage in metallic silos was the most effective in controlling mold infection and aflatoxin contamination, regardless of drying practice, while storage in polypropylene bags was the least effective. From the results, improved drying and storage technologies and practices were found to reduce postharvest maize losses, mold infection and aflatoxin level by over 50%. Use of raised drying racks and storage in metallic silos was found to be the most effective combination in maintaining maize
quality and reducing postharvest losses.

Key words: Aflatoxins, maize quality, mold infection, grain storage, postharvest losses