Appendix 3.6: Statistics for the importance of maize in Katumba ward
4.2 Materials and Methods
4.2.1 Sampling of the farm households
Farm households were sampled using the procedure indicated in Chapter Three, Section 3.2.1.
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4.2.2 Sampling of maize samples
Maize samples were randomly collected from a sub-sample of 130 households drawn from the 260 sample householdsbetween February and March, 2009. Half of the sample households was considered large enough to provide reliable findings. In order to eliminate bias and sampling error, maize sample units were randomly sampled as follows:After thoroughly mixing the maize grain 2.5 kg of maize were collected from storage facilities using the method recommended by Pitchler (2006). Where maize was in the form of cobs the cobs were mixed thoroughly ten randomly picked followed by shelling. The maize kernels were evenly distributed on a 1x1.5 m mat and divisions were made on the mat using ropes as shown in Figure 3.1, and the ropes were secured in position using nails. Maize for insect pest quantification was collected from the mat on spots represented by green circles in Figure 4.1 situated about 30 cm from each other. This procedure was used to collect maize from the sub-sample of farm households immediately after maize was harvested in March 2009, and later repeated after the same farm households had stored maize for five months.
Since the maize samples were randomly sampled it was expected that the results would be reliable.
Figure 4.1: Sampling of the maize sample units Source: Pitchler, 2006
Due to the fact that a larger proportion of the farm households stored maize using the roof storage method than the sack storage method (Section 6.1), Forty two out of the 130 maize samples were gathered from the sack storage facilities and 88 were collected from the roof storage facilities.
Moreover, the number of maize samples for each maize variety collected depended upon the
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varieties that the farm households had at that particular moment. Thus, 87 out of the 130 maize samples were of the improved varieties, 43 were of the indigenous types. Each of the maize samples was zip-locked in a separate zip-lock plastic bag in order to prevent movement of insects from one maize sample to another.
4.2.3 Data collection techniques
Semi-structured and structured face-to-face interviews were administered to 260 sample households in Katumba ward by the researcher with the help of research assistants.interviews were carried out in February - March 2008 and repeated in February - March 2009 in order to gather information which was inadequately collected in 2008. Semi-structured face -t o - face interviews were used in order to make possible the participation of those who cannot read or write (Trochim, 2006). The questionnaire that was used is shown in Appendix 4.1. The survey was later split into different sections that were used to answer the research objectives that made the chapters of this thesis. The interviews were conducted at the participants own homes or venues of their choice to make easier the participation of women. In Rungwe district most of the farming activities including processing and crop storage are done by women (FAO, 1994). Data collected included the types of storage methods that the farm household used, the length of time during which maize was stored, the quantities of maize that the farm households stored and the farm households’ perceptions concerning the capacity of the storage method to protect the stored maize from infestations and infections.
Data set concerning farm households’ experiences of maize losses due to pests, types of insects, moulds and rodents that they observed in stored maize and control methods that they used against the infestations and infections was collected. Pictures of different types of maize insect pests, rodents and ear rots symptoms (Appendix 4.1) were attached to the questionnaire and the farmers were asked to view the pictures and identify the types of insect pests, rodents and moulds that they observe in stored maize. Data set concerning the types of maize seeds that the farm households grew, whether the farm households bought or used some of their own saved maize seeds for planting was also collected. Places where they bought the seeds from, other storage problems apart from infestation and infection and means that the farm households used to dry maize was were recorded. Details concerning the collected data are shown in Appendix 4.1.
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Levels of insect infestations in the maize samples were studied using the incubation method described by Derera et al. (2001). Grain samples were each placed in a 250 ml glass jar for insect detection. The glass jars were covered with nylon mesh screen lids to prevent insects from escaping while allowing free ventilation. The glass jars were also labelled for identification of the source and maize variety and were kept at room temperature at 25 - 30 0C and 75 - 80 % relative humidity.
Insects that came out of the maize samples were counted after 90 days of incubation period. The 90 days incubation period was considered long enough to allow growth of the insects pests especially during the cold season at the University of KwaZulu-Natal, Pietermaritzburg, South Africa, where the trials were conducted. The above procedure was repeated using maize samples that were collected from the same households after five months of storage in September 2009.
Forty two out of the 130 maize samples were gathered from the sack storage facilities, whereas 88 were collected from the roof storage facilities. While 43 out of 130 maize samples were local varieties, 87 out of 130 were improved varieties.
4.2.4 Statistical analyses
Statistical analysis was performed using the Statistical Programme for Social Sciences (SPSS) version 15, 2005 software. In order to find out the number of scores per response, descriptive statistics were performed using frequencies for each response. Cross tabulations were also performed in order to explore trends between variables. Part of the statistical output is shown in Appendix 4.2 - 4.7. The amounts of maize that the farm households lost to infestations and infections were obtained by subtracting the amount that the farm households used for consumption and non-consumption purposes from the total estimated amount of maize that the farm households harvested per year4.
The estimated amount of maize produced in Katumba ward was obtained through multiplying the average amount of maize that each farm household produced per annum by the number of households in the ward, which was 2649 households. The percentage of farm households in
4Moisture content of the maize was not measured thus, changes in the grain due to changes in moisture content were not accounted for.This may affect the accuracy of the calculations.
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Katumba ward for whom insect infestation of maize started during storage was obtained through subtracting the percentage of maize samples that were found to be infested by the insect pests prior to storage from the percentage of maize samples that were found to be infested by the insect pests during storage.The average number of insect pests per kilogram (kg) of maize, were derived from the mean quantity of insect pests per 120 maize kernels (or 51 g) of maize.
The independent t-tests were performed in order to evaluate the performance of different storage methods through comparing average numbers of insect pests that came out of the incubated maize samples from each of the storage facilities. Levels of insect infestation in the landraces and improved varieties of maize were compared by conducting the independent t-test using the SPSS programme.