CHAPTER 7 STORAGE LOSSES AMONG SMALLHOLDER FARMERS AND THE ECONOMIC
7.2 Research methodology
7.2.1 On-station trial
This chapter used primary data to compare percentage weight storage losses of smallholder farmers‟ storage technologies to hermetic storage technologies. Storage loss data from the
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CIMMYT/UZ on-station trials on the effectiveness of storage technologies against maize weevil and LGB was collected over ten months between August 2012 and May 2013. The experiment was conducted at two stations; Makoholi Research Station (Natural Region IV), near Masvingo and Hatcliffe (Natural Region II), at the Insitute of Agricultural Engineering (IAE) in Harare. The sites represented the best and worst agro-ecological conditions for smallholder maize farmers in Zimbabwe, therefore the results are nationally representative.
The maize grain (variety SC 637) used for the experiment was sourced from IAE and 50 Kg super grain bags (SGBs) were procured from a GrainPro agent in Harare. GrainPro SGB is an Ultra Hermetic bag lining solution developed primarily for smallholder farmers (http://grainpro.com/gpi/index.php?option=com_content&view=article&layout=edit&id=205 ). It is made up from a multilayer recycled polyethylene plastic and can be reused. Metal silos (100 Kg) were bought from a local general engineering firm while Actellic Super Gold (commercial synthetic pesticide) and 50 Kg woven polypropylene bags were sourced from the local market. Galvanized plain iron sheets were used to fabricate the metal silos. The grain was exposed to the sun before storage and thus was dried to 13.5% moisture.
A Completely Randomised Design (CRD) was used to set up the experiment consisting of four treatments namely; the Metal silo, Super grain bag (SGB), Actellic super gold treated polypropylene bag and untreated polypropylene bag. These treatments were replicated three times under natural and artificial modes of infestation. Under natural infestation, the grain was not disinfested initially and no insect was introduced to each storage structure while, for artificially infested treatments, grain was initially fumigated using Phostoxin® tablets at label rate for seven days to disinfest any possible prior infestations. A mixed adult insect population of S. zeamais and P. truncatus was then added to each replicate treatment at a ratio of one insect/kg of grain. No pesticides were added to metal silos and SGBs treatments and each replicate were 40kgs to allow easy tying and create a hermetic environment. The air was squeezed out of the SGB and a zipper slider was used to tie the triple bags, thus creating the hermetic environment. The metal silo‟s outlet lid was also completely closed and tied with a rubber band before loading the grain. Grain was loaded using a bucket to avoid pressing the inlet lid and then two burning candles were placed on metallic candle holders and left to burn out. The inlet lid was then closed with a top cover and completely sealed with a rubber band. The assumption is that candle burning will deplete O2 and fasten CO2 build up in the metal silo.
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Baseline grain samples were then collected at trial setup and non-destructive sampling method was carried out thereafter, at 30-days interval for ten months using double tube multi- slotted brass sampling spears. At each sampling interval, an equal sample of 0.5 Kg per replicate was withdrawn. The sampling spear was inserted at different corners of the metal silo and bags to withdraw the samples. Care was also taken to maintain the hermetic conditions of the hermetic technologies by following the procedures described above.
Samples were then separated to grain, insects, and dust using 4.7 and 1.0 mm sieves. Various data were recorded including the number and weight of damaged and undamaged grains, live and dead insects, the weight of dust produced and number and weight of rotten (mold) kernels. This study is interested in the percent weight loss data for use in the economic analysis. To estimate the percentage weight loss, collected samples were assessed by the conventional „Count and weigh‟ method. Sampled grains were separated into damaged and undamaged, weighed, numbers counted and percentage weight losses for each sample were determined using the formula (Adams and Schulter, 1978):
Weight loss (%) = *100
Where, = Weight of undamaged grain, = Number of undamaged grain, = Weight of damaged grain, and = Number of damaged grain.
The percentage storage weight loss data was thus collected from the on-station trials and used to perform the economic analysis of hermetic storage technologies versus farmers‟ storage technologies. In the economic setup, four storage technologies namely the metal silo, super grain bag, actellic treated polypropylene bag and untreated polypropylene bag were also used.
Actellic super gold insecticide is one of the two commonly used storage chemicals by smallholder farmers in the country. Percentage weight loss data from naturally infested treatments were used in the analysis to mimic storage conditions at smallholder farm level.
Paired t-tests were run in STATA 13 to test the differences between mean percentage weight losses of farmers‟ storage technologies versus hermetic technologies.
Mean storage losses comparisons between the treated bag and the untreated bag were left out as both are farmers‟ current storage technologies. Likewise, there was no comparison of the two hermetic technologies since the farmers‟ practice can only compare their current technologies to either of the hermetic technology options. An incremental approach was used to determine costs of switching from current farmer storage technologies to either a metal silo
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or super grain hermetic bags. Two common farmer storage technologies of storing shelled grain in polypropylene bags with and without insecticides were controls in this analysis.
Bagging is the commonest storage practice in Zimbabwe among smallholder farmers.
Interviews with metal silo manufacturers, farm inputs retailers and government officials provided data on input costs, for example price of one tonne metal silo (made using galvanized plain iron sheet), retail price of 50kg super grain bag (Grain pro), 50kg polypropylene bag, candle and rubber band (used for sealing the inlet and outlet openings of metal silo to create an airtight environment), 500g of actellic super gold and monthly maize grain prices between August 2012 and May 2013.
CBA of metal silos and super grain bags for storing one tonne of maize grain over 15 years was done against farmers‟ current technologies. The life span of the storage investment was taken to be 15 years (Kimenju and de Groote, 2010), therefore the costs and benefits were the sums of the whole life of each storage technology. Super bags are considered to last for two years and have to be replaced thereafter (following perforation by LGB). The costs and benefits were replicated till they had the same useful life with a metal silo to allow for comparison of NPVs (Kassa, 2015). The benefit of storage in this study was taken as the physical weight loss that is abated due to the use of new storage technologies.