Since the introduction of rice in Uganda in 1904, insufficient information has been generated on quantitative rice postharvest losses. Such inadequate information has partly constrained decision making in developing the rice industry in Uganda. The objective of this study was, therefore, to generate quantitative postharvest losses in the remaining two major rice growing hubs of Albertine and Olweny. The AfricaRice postharvest loss assessment methodology was used during the two growing seasons of 2014 /15 and 2015/16. Data was collected at harvesting, threshing, drying and milling postharvest stages on 10 rice farms and nine rice mills in each hub. The swamp rice “K98” and “NERICA-4” both in Oryza Sativa group were used during the study in the Olweny and Albertine hubs respectively. The results indicated that total physical grain losses at aforementioned stages in Albertine and Olweny hubs were 16.8 and 14.1%, respectively. This slight loss variation could be attributed to the different varieties and postharvest practices in these hubs. Losses at harvesting exhibited highest value 6.9 and 5.7% compared to threshing 4.7 and 4.8%; drying 1.8 and 1.4%; and milling 4.8 and 3.5% for Albertine and Olweny hubs respectively. There was no significant difference (p>0.05) discerned in the losses between the hubs. Regardless of the rice hub, significant differences in loss levels (p<0.05) existed along the postharvest operations. These results show that harvesting, threshing and milling were the critical control points in the management of quantitative rice postharvest losses in Uganda.
In quest to ensure food security and alleviate poverty, reduction of food postharvest losses becomes critical 1 . Quantitative rice postharvest losses in sub Saharan Africa, range between 25.6% and 27.4 % along the production chain 2. The high postharvest losses have been attributed to poor post-harvest practices and use of inappropriate equipment 3 . Since the introduction of rice in Uganda in 1904 7 , not much has been done to comprehensively understand quantitative postharvest losses of rice in the country 5 . The flaws in previous rice postharvest studies included lack of simple, adoptable and well-defined practical methodology to credibly quantify the physical losses as evidenced by wide variation in post-harvest loss results reported in literature 2 . In addition quantitative postharvest losses are dependent on location, postharvest stage, rice variety and postharvest practices. The study by Saunders et al. (1980) estimated that the total weight losses of rice in Uganda along the postharvest chain was 11 %. 5 reported that the on-farm postharvest loss for Kaiso rice variety at harvesting, threshing, drying and cleaning operations in the eastern rice hub was 13.5 %. However, the wide variation in post-harvest loss results reported in literature has created incertitude in the methodologies of the researchers (Affognon et al., 2015). To address such gaps this study used a comprehensive 3 postharvest loss analysis methodology to quantify and understand actual rice postharvest losses in Olweny and Albertine rice development hubs of Uganda. Generation of accurate information was very instrumental in determining the critical control points where efforts should be focused to control postharvest losses.
Materials and Methods
2.1 Scope of the study
The study was conducted in Albertine and Olwenyi Rice hubs, located in the districts of Hoima and Lira, respectively (Figure 1). The hubs are among the three major rice growing hubs of Uganda. Hoima and Lira districts were selected because rice production, processing and marketing is highest in their respective hubs. Data was gathered at smallholder rice farms, farmers, cottage mills, millers and extension staff who were purposively selected from the mentioned districts. It was collected during 2015 and 2016 harvest seasons from a total of 20 farms in nine villages and 20 rice milling plants from eight towns spread across the two hubs. Specifically, data was collected at the four stages envisaged to be critical in postharvest value chain and included: harvesting, threshing, drying and milling.
2.2 Rice varieties used in the Study
The study focused on two rice varieties; “NERICA-4 for Albertine hub” and “Kaiso, K98” for Olweny hub. The two varieties were selected on the basis, they were the most grown and traded varieties in the respective hubs. More so, these varieties have different characteristics given that the two hubs fall in different agro-ecological zones. “NERICA-4” is a rice variety grown mainly in upland while “Kaiso, K98” is a lowland variety
2.3 Procedures for data collection
The AfricaRice (2012) developed protocol for rice postharvest loss assessment was adapted and used to collect the data. Rural smallholder farmers and cottage rice millers were purposively sampled because of their important bearing in the rice production sector. As mentioned in section 2.1, the focus was on harvesting, threshing, drying and milling stages (Figure 2) of rice post-harvest handling operations. The data on physical losses were measured in the rice gardens and at cottage rice milling plants. The grain losses in the garden were determined on the same day when a farmer chose to harvest his/her rice, meanwhile, processing losses were determined during milling. The total physical quantitative losses were determined using equation 1.
Data analysis was divided into two parts. The first part employed the use of descriptive statistics to describe means of grain losses within the individual postharvest operations. The second part involved application of two experimental designs. The first experimental design, a 2 X 2 CBD was used to compare the means of grain losses across the two rice hubs and varieties. Rice development hubs (2 treatments: Albertine and Olweny)) and varieties (2 treatments: NERICA 4 and Kaiso, K98) were the two independent factors that influenced grain losses across the two locations. NERICA 4 and Kaiso, K98 were the rice varieties used during this study in Albertine and Olweny hubs respectively. Two-way ANOVA, LSD method was used in analysing the data from this experimental design. The second experimental design was to compare means of grain losses along the different postharvest operations within a hub. This design had postharvest operations as the only independent factor and had 4 treatments: harvesting, threshing, drying and milling. One-way ANOVA, LSD method was used to compare the means of grain losses along these treatments. SPSS version 16.0 and MS Excel Computer Soft-wares supported the data analysis and processing.
Results and Discussions
4.1 Harvesting grain losses
The grain physical loss obtained at harvesting stage was due to grain shattering during cutting of straws, in-field-stacking of the harvested straws and transportation of the straws to a central threshing point and the investigated results are shown in Figure 3. The results showed that physical grain loss at harvesting stage in the two hubs was still high ranging between 6.93 ±1.79% and 5.68 ±2.01% for Albertine and Olweny hubs respectively. The losses due to shattering had the lowest values while in-field-stacking registered the highest amount.
The grain losses due to in-field-stacking were almost the same as values earlier obtained by Candia et al. (2012) in the Eastern hub of rice development. By contrast, results due to shattering in this study indicated lower values. The newly generated lower levels could have been attributed to farmers harvesting their paddy at the correct harvesting time and during good weather conditions. There was no significant difference (p>0.05) in harvesting losses between the rice hubs. Regardless of the Rice hub, significant differences (p<0.05) existed between sub-stages of harvesting. Although statistically there was no difference in grain loss at these two hubs, Albertine had still higher grain loss (7%) than Olweny hub (5.5%). Grain moisture content is a critical factor in influencing shattering. The results indicated that the mean moisture content of paddy at harvesting in Albertine and Olweny hubs were 20.43 and 23.79% (w.b.) respectively. The moisture content of paddy in Albertine is slightly below the recommended lower limit of 22% for harvesting. Considering the very low shattering properties of NERICA 4 variety, the high grain loss at harvesting stage in Albertine hub could be attributed to hot weather conditions during the harvesting time (November – December) in this region. The hot weather makes the grain lose moisture much faster than expected. This accelerates grain shattering and hence high levels of grain losses. In comparison to similar studies elsewhere, the total harvesting losses due the same harvesting technologies correlated very well with those obtained in Ghana which ranged between 4.07 and 12.05% (Appiah et al., 2011)
4.2 Threshing losses
The grain losses at threshing stage consisted of losses due to incomplete removal of grains from the ears of the rice straw pinnacles, scattering of grain because of the impact force from beating stick and social behaviour of hired labourers. The study results showed that grain losses were 5.48 and 5.69% during threshing by beating method in Albertine and Olweny hubs respectively. These results were consistent to those reported by Candia et al. (2012) for Eastern hub (3.1 – 6.4%) and Appiah et al (2011) for Ghana (3.94 – 6.96%). Although rice varieties grown in the two hubs were different, no significant difference (p>0.05) was discerned in the losses between the hubs (Figure 4).
Conclusions and recommendations
The total physical grain loss at the different hubs was 16.8% and 14.1% in Albertine and Olweny respectively. On average physical rice grain loss in the study hubs was 15.45%. Further, post-harvest operations viz. harvesting, milling and threshing were the critical control points in the management of quantitative rice postharvest losses in Albertine and Olweny hubs. The obtained loss values are highly significant not only of their adverse economic impact, but equally threatens food security to farming families. To achieve successful maximal loss reduction, the promotion of specific technologies focusing on on-farm improvement should be established and there should be provision of the technical support to the farmers along the different postharvest stages. Investments in further research aimed at developing cost-effective and appropriate technologies can provide momentous gains in the effort to reduce these losses at farm level.
The authors are indebted to Global Affairs Canada (GAC) for funding this research through Grant no. A034968 and AfricaRice for technical support. The authors would like to express their sincere gratitude to rice farmers and millers who voluntarily provided their facilities for use in this study.