Controlling the deterioration of harvested grain/seed to improve food security

Darfour, Bernard
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The agriculture sector is the largest source of employment for Ghanaians and it is dominated by smallholder farmers. The challenges in the agriculture sector are many which include food insecurity. Maize offers a significant source of calories, and accounts for 50% of the total cereal production in Ghana, with the reported postharvest loss (PHL) between 5% and 70%. Improving food security through a reduction of PHL is imperative for meeting current development objectives. Sitophilus zeamais can inflict serious damage to maize in storage leading to about 20% to 50% or more losses within 3 to 6 months. The lack of industrial processing of maize and improper storage facilities have compelled farmers to sell their bumper harvest at low prices, and stored grains get rotten. Grain or seed deterioration caused by insects, diseases, rodents, physiological or chemical changes, and pathogenic microorganisms can be minimized by applying appropriate storage and treatment techniques. About 80% to 90% of Ghanaian farmers use pesticides, and about 20% of pesticides used across the world could be found in developing nations, and this poses environmental and health dangers. Complete dependence on pesticides is unsustainable, and the environmental and health implications are unavoidable. Synthetic chemicals although effective against S. zeamais, they are misused or misapplied exposing farmers and consumers, and the environment to unforeseen risks. The overall objective of this research was to use non-chemical techniques to control the deterioration of stored grain/seed to minimize food insecurity, and to improve the financial security of farmers.

Small-sized grains like sorghum are important for food security. Hence, the storability of organic and conventional sorghum grains at constant RH and different temperatures was studied. Susceptibility of the two grain types to S. zeamais, grain moisture, and rate of changes in O2 and CO2 concentrations in hermetic jars were similarly considered. Organic and conventional sorghum grains were stored in an environmental chamber at 15oC, 20oC and 30oC, and 75% RH for 0, 15 and 30 days. The daily CO2 and O2 concentrations measured in the hermetic jars showed an increase in CO2 and a decrease in O2 as the temperature increased. The changes in CO2 and O2 concentrations in the hermetic jars might have resulted in the 100% S. zeamais Mortality. The quality and quantity of sorghum grain stored in hermetic jars were maintained, especially at low temperatures.

Further, the environmental impacts assessment and cost analysis of the active ingredients in actellic super (pirimiphos-methyl and permethrin) and NeemAzal (Azadirachtin) for maize grain treatment were evaluated. A functional unit of 1 kg of grain or insecticide was used in the analysis. Pirimiphos-methyl manufacturing had the lowest CO2 emissions and impacts (mPts/kg), and permethrin manufacturing had worse CO2 emissions and impacts. The CO2 emissions and impacts were severe when pirimiphos-methyl and permethrin were air shipped, hence sea transport is encouraged. Pirimiphos-methyl usage had the highest ecotoxicity impacts, and permethrin had the least. Azadirachtin had no human health impacts, however, pirimiphos-methyl exhibited human health impacts while permethrin was negligible. The price of the NeemAzal was 224% high compared to actellic super as NeemAzal is applied in a larger quantity.

A semi-structured questionnaire was used to collect data on the different kinds of pre-harvest and post-harvest losses that maize farmers in Ghana encounter, storage practices, and farmers’ awareness and knowledge of mycotoxin contamination. The male maize farmers were many compared to females, and at least 70% of farmers were over 40 years of age. Over 50% of farmers except the Northern region completed at least basic education. At least 90% of farmers experienced at most 2% pre-harvest losses. Farmers observed PHL of between 60% and 100%. Typically, grains were stored in polypropylene bags for 3 to 12 months. Farmers used synthetic insecticides, and pepper or basil or neem plant materials to control maize weevils during grain storage. The Northern region had the highest usage of plant material for grain treatment, and the least maize weevil infestations.

In addition, the efficacy of the periodic physical disturbance method on S. zeamais mortality, and the adoptability of the method by subsistence farmers in Ghana was studied. The maize grains were non-hermetically stored in plastic buckets for 30, 60 and 90 days at 27±5oC. The buckets were physically disturbed for about 2.5 minutes twice a day. The physical disturbance did not cause any significant S. zeamais mortality. The failure of the method could be due to human error or the large number of S. zeamais used inundated the technique or the high temperature, RH and grain MC favored the growth and development of S. zeamais. Importantly, despite the failure of the method in causing S. zeamais mortality, the quality of grain in the disturbed buckets was maintained.

The study also considered the evaluation of the advantages of GrainPro bags over woven polypropylene bags during maize grain storage. All the woven polypropylene bags but no GrainPro bags were damaged by S. zeamais. The percentage of damaged grain in woven polypropylene bags was between 91.9% and 94.4%, and from 0.2% to 0.7% in GrainPro bags. Hundred percent S. zeamais mortality was achieved in the GrainPro bags compared to less than 10.0% in the woven polypropylene bags. Grains were better stored in GrainPro bags compared to woven polypropylene bags.

Similarly, the study also focused on seed storage using zeolite beads. Maize seeds of the same variety at 15.3%, 11.3%, and 9.8% moisture were stored in airtight glass jars for 1, 3 and 6 months. Seeds at 15.3% MC stored without zeolite beads had increased moisture, and decreased germination and vigor. Seeds at 11.3% and 9.8% MC stored with or without zeolite beads had moisture maintained or decreased, however, germination and vigor increased. Germination linearly increased from 91.0% to 99.0% during the 1 to 6 storage months. The SGR at 6 months was generally high. Maize seeds with high initial MC can be stored safely, and lose moisture during storage when using zeolite beads. Zeolite beads did not negatively affect seed germination and vigor, and therefore an alternative to seed refrigeration.

Further, the cost-effectiveness of five different maize grain handling techniques was studied with computer simulation. The annual capital and operational costs of using m. silo + acc. or m. silo were so high, and the expenditure could only be afforded through farmers-cooperatives. But the capital and operational costs of using either PICS or w. PP. + Phos. or w. PP. were comparatively so low, and most individual farmers could afford. The annual capital and operational costs decreased with the increased scale of production. Using PICS or w. PP. or w. PP. + Phos., the breakeven was reached even at the low production scale of 2.8 Mg. Nonetheless, the high percentage of grain losses mostly related to using w. PP., and w. PP. + Phos. should not be disregarded. Handling grain mechanically with m. silo + acc. or m. silo through a farmers-cooperative could improve food security and financial prospects of farmers. Individually, PICS bags or other hermetic bags rather than w. PP. or w. PP. + Phos. could be used to improve food security and income security.

Economic analysis, Food security, Ghana, Grain and seed, Maize, Post-harvest storage