Proper post-harvest handling practices are important in maintaining grain quality and safety while being brought to consumers and for trade. However, lack of knowledge among the smallholder farmers and other factors along the value chains remains a major challenge to reduce postharvest loss and maize grain contamination by aflatoxins in Sub-Saharan African (SSA) (Kachapulula  et al., 2017).  Weather conditions and poor postharvest management practices have been reported as the major factors of fungi infestation and subsequent production of aflatoxins in crops (Suleiman et al., 2017). Moreover, different measures like good agriculture practices (GAPs) such as timely planting and harvesting, the use of resistant   crop    varieties,   good   storage  (at  controlled humidity and temperatures) combined with good manufacturing practices (GMPs) (sorting and grading) were reported to be of help to combat the problem of PHLs and mycotoxins contamination in grains (Massomo, 2020). However, the implementations of these measures are not well understood by the majority of smallholder farmers in SSA.

Post-harvest losses (PHLs) remain a persistent challenge in Africa. According to the World Resources Institute, approximately twenty-three percent (23%) of the available food in SSA is lost or wasted (Global knowledge Initiative, 2014). It has been reported by the Food and Agricultural Organization of the United Nations (FAO) that, around 2 million African smallholder farmers would benefits in terms of  income and increased food and nutritional security through the reduction of PHLs.

Maize (Zea mays) is a major food staple in Tanzania, and its production is dominated by small-scale farmers who constitute about 75% of the total production (URT, 2019). It is widely cultivated all over the country. Maize accounts for 31% of the total food production, constitutes more than 75% of cereal consumption and contributes about 34 to 36% of the total average daily calorie intake in Tanzania (Zorya et al., 2011). In the country, maize is used to prepare varieties of meals including ‘Ugali’, ‘Makande’, porridge and traditional alcohol. The importance of maize in Tanzania suggests that serious efforts must be made to reduce crop losses at all levels, especially in the post-harvest part (Suleiman and Rosentrater, 2015).

The problem of food shortage in developing countries could be overcome through the use of a variety of modern agricultural technologies (URT, 2012). Experience shows that the Tanzanian government's efforts to improve the agriculture sector have resulted in increased food crop production including maize. Despite increased maize production, periodic food shortages have been experienced, one of the reasons being PHLs of cereal such as maize (Twilumba et al., 2020). In Tanzania, PHL remains a serious and persistent challenge; the current level of PHL of maize is 20 to 40% in some rural areas which have a significant impact on food security and the economy of the smallholder farmers (Maziku, 2019).

Improving postharvest management practices could help mitigate losses along the maize value chain and contribute to poverty reduction and food insecurity in the country. Farmers must have to access and understanding of good postharvest practices in order to ensure food availability throughout the year. The good postharvest practices include proper harvesting/drying practices, good transport infrastructure and the use of improved storage technologies, such as hermetic storage bags and metal bin/silo. This could help to decrease the problem of PHLs in Africa (Twilumba et al., 2020). The study's findings will help smallholder farmers reduce PHLs as a result increased food security. Furthermore, data would guide the selection of better intervention steps in order to ensure public safety.

Study area

The study was conducted in Kondoa and Chemba districts in Dodoma region, Tanzania (Figure 1). The area is mostly semi-arid due to low and erratic rainfall. Kondoa District lies between latitude 4° 12` to 5° 38` South and longitude 35° 6` to 36° 2` East. Chemba District lies between 5° 14` to 36° 00` South and longitude 35° 53 to 24° 00 East. Its climate is wet savannah characterized by a long dry season (DEPRP, 2012). The districts were purposively selected due to multiple threats affecting the districts including drought, deforestation, soil degradation and hunger, imposing a pattern of risk evasion in traditional agriculture (URT, 2017).

Research design, sampling procedure and sample size

This study adopted cross-sectional research design and a multi-stage sampling technique as suggested by Etikan and Bala (2017). First, the district was purposively selected based on the reasons stated above. Secondly, simple random sampling was employed to select study villages. Thirdly, one hundred and twenty (120) respondents were randomly selected from smallholder maize farmers.

Data collection procedure and instrumentation

Data were collected in face-to-face interviews with respondents by using a semi-structured questionnaire, which were all pre-tested for improvement before actual data collection. The statement-wise analysis was carried out to determine the most post-harvest practice applied by respondents; nineteen statements were used to measure the respondents' understanding of post-harvesting practices as shown in INPhO-Post-harvest Compendium (Mejia, 2013). For each statement, the respondents were required to indicate their position concerning their level of understanding of the content contained in the statement by writing one (1) for poor practice, two (2) for moderate practice and three (3) for high practice. If one practice was marked poor for each of the 19 statements, it was scored 19 (i.e. 1 × 19); if one practice was selected moderate for each of the 19 statements, it was scored 38 (i.e. 2 ×19); and if one practice was selected high for each of 19 statements, it was scored 57 (that is, 3 ×19). Scores were combined to give a score range of 19 to 57.

A score above 19 was considered as highly experienced practice, a score of 19 represented moderately experienced practice and a score below 19 indicated poorly experienced practice. The mean score of each practice was obtained by adding the weights given to the standard by a respondent divided by the total number of respondents. The mean score was worked out for each practice and rank positions were assigned based on the mean score obtained after calculation.

Data analysis

The collected quantitative data were coded, entered in Statistical Package for Social Sciences (SPSS), edited and analyzed using the SPSS version 20 Computer software. Descriptive statistics for different measures were performed to compute relative variables. The mean, standard deviation of post-harvest handling for each district were computed. Correlation analysis was undertaken to determine which handling practices were found to be common.

Demographic characteristics of respondents

The socio-economic and demographic characteristics of the smallholder farmers and their  effects  on  handling  of post-harvest maize management technologies were analyzed. Therefore, respondents responding to questions that were related to their gender, age (The actual age of the respondents was recorded during data collection and later categorized into groups), levels of education   and  land  family  size.  Their   responses  are illustrated in Table 1.

Postharvest handling practices used by respondents

Table 2 shows the different handling practices done by respondents in the study area. The smallholder farmers in Kondoa and Chemba districts do not have a long chain from harvesting to storage. They only harvest, transport, shell/thresh, clean, dry and finally store for consumption or sale purposes; the grains are typically stored in a living room in the house or a brick and mortar storeroom. Some of the farmers produce only for consumption while others produce as food and cash crop.

Post-harvest practices mostly used by respondents

To establish the extent to which the practice was applied by smallholder farmers, a statement-wise analysis was carried out. The mean score was worked out for each practice and rank positions were assigned based on the mean score obtained after calculation (Figure 2).

Furthermore, the majority of small-holder maize farmers used traditional knowledge in maize handling management (Figure 3), implying that poor postharvest handling practices and low awareness levels among maize farmers. That can lead to postharvest losses due to poor handling practices and improper management, posing a threat to human food safety. This necessitates interventions aimed at improving postharvest practices.

Traditional storage technology

The findings (Table.2) show over 80% of the respondents use polypropylene/synthetics bags with or without pesticides to store their maize. The disadvantage of using polypropylene sacks (bags) is that they can be easily destroyed by pests and are not airtight thus grains are prone to insects and fungal contamination. This concurs with the finding of Mendoza et al. (2017) who observe over 81% of farmers upon drying prefer to store maize in polypropylene bags. It was also observed that only 3% of the respondents use traditional storage structures (Kilindo) for the storage of maize. This type of storage is locally constructed and was found in store rooms or living rooms. Minority of the respondents (3%) from the study area store maize in a homemade gallery (Figure 4). This finding is similar to what was reported by Gitonga et al. (2015) and Abass et al. (2014) that most of the African communities still rely on unimproved storage technologies for maize storage. This is because they are simple and inexpensive to construct but cannot guarantee protection against major storage pests and quality product.

Insect control

The researchers noted that nearly half  of  farmers  (46%) use pest controls, whereby the commonly used was chemical pest control (26%) and traditional pest control (20%); while 54% use sun-drying. This could be due to the cost of storage chemicals which was perceived by respondents as relatively high and therefore not affordable for them to buy. However, the effectiveness of traditional insect control methods such as the use of ash, Shumba is not known and needs to be evaluated further.

Few smallholder farmers pointed out that storing their maize in their houses thus making it difficult to apply pesticides or fumigate the living rooms for storage of their maize. These findings are contrary to those of ANSAF (2016) which found that a large proportion of farmers (67.7%) in Dodoma and Manyara districts of Tanzania use storage chemicals. Likewise, Koskei et al. (2020) found that (70.7%) use chemical insecticides while 32.5% use ash to insect control infestation.

Post-harvest practices mostly used by respondents

The highest mean score of mostly used handling practices is 2.78 (Figure. 2), that means the storage methods mostly used by respondents “Polypropylene/ synthetic bags as storage practices”. These results reveal that stored maize is a very important subject for sustainable food security in the production of maize areas. It helps the farmers on how to store food for future use. However, polypropylene bags are not recommended in post-harvesting practices because they are not airtight; hence, they are susceptible to water and are easily accessed by pests and rodents.

Moreover, polypropylene bags are considered as spillage and easy inspection. The study findings revealed that smallholder farmers were highly practicing this practice which has a direct negative effect on the quality of the maize produced.

The second-highest ranked practice used was the way of shelling/threshing of maize, “that was Hand shelling/ threshing” demand (2.40) manual shelling (beating maize in bags). The process is done to loosen the edible part of grain from the straw to which is attached after drying to facilitate easy storage of grain. The practice is not recommended because losses were in terms of broken grains. This is followed by “Harvesting maize and placing on the ground” (2.38) which ranked third. This practice was highly practiced because the majority of smallholder farmers use local equipment or traditional way in harvesting their maize. The practice is unhygienic because it exposes the maize grain to soil contamination and bad weather infection causing both quality and quantity losses; although it is also considered to be slow and time-consuming.

Other practice methods were drying maize “by spread on the ground” (2.16), which ranked fourth  and “Time used to dry maize more than one month” (2.05) ranked fifth .These practices were highly implemented because majority of smallholder farmers are still using traditional post-harvesting handling practices. Additionally, the findings show that 75% of the respondents had used traditional practice on maize post-harvesting processes and only 25% used modern practice (Figure 3). These results imply that about half of the respondents in the study area practice traditional post-harvesting. Traditional technologies are poor in maintaining the quality and quantity of stored maize but most of the smallholder farmers argue that these traditional practices are easy, inexpensive and it is not safe compared to new post-harvest practices technology. This affects the quality of maize as poor postharvest practices expose the maize grains to contamination that might have health effects on human. Maize is a staple crop for many farmers in the country. There is a need to improve and promote postharvest handling procedures, including the use of modern technology like moisture meters, portable dryers, and hermetic storage devices. Therefore, it is necessary to awake farmers about appropriate post-harvesting techniques to reduce the amount of post-harvest losses in maize production and thus contribute to food security and poverty reduction.

Postharvest loss is a complicated issue and its scale varies with different crops, handling practices, climatic conditions, and countries' economy. Many of the harvested maize grains are held in traditional storage structures, which are insufficient in preventing insect infestation and mold  growth during  storage,  resulting  in significant losses. Generally, the respondents' postharvest behaviors were linked to postharvest losses, indicating that they lack awareness of optimal postharvest techniques. However, few of the farmers were aware of improved post- harvest technologies, but cannot afford to buy as it is sold at a high price, since their income is very low. Storage losses account for the bulk of all postharvest losses for maize grains in the study area, hence have a negative influence on farmers' livelihoods. Reduced postharvest losses and increased farmer revenues can be aided by technological interventions and improved storage structures.

The authors have not declared any conflict of interests.

The authors heartfelt thank the Chief of Government Chemist Laboratory Authority (CGCLA) for permission and financial support and all farmers and Agricultural Extension officers in Chemba and Kondoa districts for their support that facilitated completion of this work.