*3.2. Pests in Experimental Trials*

Regarding the pest infestation, the treatments including the chemical conservation measure recorded the lowest insect populations. Application of the chemical conservation measure decreased the infestation by insects significantly. As a result, the application of the chemical conservation measure improved the efficacy of control of the insect population. The treatments most affected by these pests were, in decreasing order, the improved clay granary without a chemical conservation measure, the polypropylene bag without a chemical conservation measure and the metal silo without a chemical conservation measure. The PICS bag and the ZeroFly® Bag without chemical conservation measure recorded a lower insect pest population. Therefore, these two technologies are likely to better protect stocks against insects.

*Sitophilus zeamaïs* was the primary pest counted, and a few *Dinoderus* spp. were observed during the identification carried out in the laboratory for the first year. In Savalou, there was a heavy infestation of grain stocks by beetles. In Boukoumbé, the number of beetles counted for all treatments remained relatively lower compared to the count carried out in Savalou. For two years, *Sitophilus zeamaïs* (primary) and *Tribolium castaneum* (secondary) were the two main pests (insects) counted during the identification carried out in the laboratory. In Savalou, we noted a high infestation of grain stocks by these two beetles, the most abundant of which was *Sitophilus zeamaïs*. In Boukoumbé, the same insects were counted, and the most abundant was *Tribolium castaneum*. However, the number of insects counted at all the treatments remained relatively lower in Boukoumbé than in Savalou.

#### *3.3. Financial Analysis of the Treatments Implemented*

The results from the evaluation of the loss rates of the treatments were used to calculate the amount of financial loss at the level of each treatment. Details on monthly costs of maize storage in each storage structure involved in trials are presented in the supplementary materials, Tables S1–S4.

#### 3.3.1. Storage Costs

The results showed that the fixed costs for the metal silo with (25.88 FCFA/kg) and without (31.61 CFAF /kg) chemical conservation measures, and the improved granary with (15.67 CFAF/kg) and without (26.1 CFAF/kg) conservation measure were statistically superior to that of the polypropylene bag and PICS bag (*p* < 0.001), whatever the municipality (Tables 3 and 4). The same trends were observed with regard to total costs, which involved both fixed and variable costs. In fact, the storage structures with a long lifespan (metal silo and improved earthen granary) had total maize storage costs of more than CFAF 100/kg while storage structures (polypropylene bag and PICS bag) had total storage costs of less than CFAF 100/kg. This was explained by the fixed costs and costs

related to financial losses, which were statistically higher for the structures with a long lifespan, especially without lifespan (F = 3.24, *p* < 0.05). This referred to the case of the metal silo without a chemical conservation measure, whose fixed costs and costs related to financial losses were higher than those of other treatments. The market price of maize does not vary according to the storage structure or whether the producer has used a chemical conservation measure. Thus, the discounted income, which corresponded to the selling price of one kilogram of maize, did not vary according to treatment, and the discounted income was CFAF 498.93 per kilogram of maize stored over a period of 6 months in Savalou.

The total costs of storing maize were all less than CFAF 100 in the commune of Boukoumbé (Table 4). The statistical difference showed that the lowest cost of storage of maize was recorded at the level of the polypropylene bag without a chemical conservation measure (CFAF 54.55) (F = 1.46, *p* < 0.05). The metal silo with chemical conservation measure, on the other hand, recorded the highest total cost of storing and conserving maize (CFAF 90.87). The improved clay granary without a chemical conservation measure recorded the highest financial loss (CFAF 9.24), while the PICS bag with a chemical conservation measure recorded the lowest financial loss (CFAF 2.07) (F = 1.46; *p* < 0.05) (Table 4). The discounted income was CFAF 389.30 in this commune for one kilogram of maize stored for six (06) months.

#### 3.3.2. Benefit–Cost Ratio

The calculated benefit–cost ratios were all greater than 1, and, therefore, when the producer invested 1 CFAF for the storage and conservation of one kilogram of maize, he or she obtained an income of more than 1 CFAF /kg. In Savalou, the storage of maize in the PICS bag (10.87), polypropylene bag (7.89) and improved granary (7.53) without chemical conservation measure, by order of priority, had the highest benefit–cost ratio compared to other structures (F = 2.01; *p* < 0.05) (Table 3). In other words, the storage of one kilogram of maize in the PICS bag, polypropylene bag and improved granary without chemical conservation measures generated an income of 10.87, 7.89 and 7.53 CFAF, respectively for an investment of 1 CFAF /kg.

The polypropylene bag had an average benefit–cost ratio that was statistically lower than that of the PICS bag without chemical conservation measure. This means that producers of maize in Savalou can use all the other maize storage structures and chemical conservation measures except the untreated PICS bag for maize storage in place of the polypropylene bag with chemical conservation measures. In the same vein, the lowest value of the income generated was observed, especially at the level of the metal silo, with (4.58 CFAF /kg) and without (4.00 CFAF /kg) chemical conservation measures. Therefore, storing maize in the improved granary without a chemical conservation measure gave the lowest benefit–cost ratio. In Boukoumbé, the storage of maize in the polypropylene bag and PICS bag without a chemical conservation measure generated an income of 7.42 and 7.30 CFAF /kg, respectively, for an investment of 1 FCFA. This was statistically higher than the value generated by the other storage structures (improved clay granary, metal silo with or without grain treatment) (F = 14.01; *p* < 0.001) (Table 4). Unlike Savalou, the income generated with the storage of maize in the polypropylene bag was relatively higher than the PICS bag without a chemical conservation measure in Boukoumbé. Consequently, producers in Boukoumbé should use the PICS bag with a chemical conservation measure in place of the polypropylene bag with a chemical conservation measure or the improved clay granary with or without a chemical conservation measure in place of the polypropylene bag with a chemical conservation measure.


#### **Table 3.** Benefit–cost ratio and break-even quantity of the different treatments implemented in Savalou.

\* = Average selling prices of one kg of maize is 498.93 CFAF in Savalou; *p* > F probabilities are indicated by symbols: ns = no significant differences; \*\* = significant differences at *p* < 0.05; \*\*\* = significant differences at *p* < 0.01. For each column, values with the same letter indicate no significant differences at 5%. Source: Experimentation data, 2015, 2016 and 2017 (− ctrol = without chemical conservation measure; + ctrol = with chemical conservation measure).

**Table 4.** Benefit–cost ratio and break-even quantity of the different treatments implemented in Boukoumbé.


\* = Average selling prices of one kg of maize is 389.30 CFAF in Boukoumbé; *p* > F probabilities are indicated by symbols: ns = no significant differences; \*\* = significant differences at *p* < 0.05; \*\*\* = significant differences at *p* < 0.01. For each column, values with the same letter indicate no significant differences at 5%. Source: Experimentation data, 2015, 2016 and 2017 (− ctrol = without chemical conservation measure treatment; + ctrol = with chemical conservation measure).

#### 3.3.3. Break-Even Quantity

The break-even quantity is the minimum quantity that the storage technology can contain to allow the producer to return on an investment for the purchase of the storage structure. In general, in the two municipalities, the results indicated that a large quantity of approximately one ton must be stored in the metal silo to make the investment profitable. In fact, considering its initial investment, the metal silo presented a large break-even quantity compared to all the other technologies (F = 16.05 *p* < 0.001 in Savalou; F = 1.03 *p* < 0.001 in Boukoumbé) (Tables 3 and 4). The break-even quantity was variable depending on the treatment. In Savalou, the metal silo without grain treatment presented a breakeven quantity value of 848.86 kg compared to 821.35 kg for the metal silo with grain treatment (Table 3). The polypropylene bag without grain treatment had a threshold capacity of 31.24 kg compared to 30.97 kg for the polypropylene bag with grain treatment (Table 3). The PICS bag without grain treatment presented a break-even quantity of 97.94 kg compared to 98.52 kg for the PICS bag with grain treatment. The closed ground granary without grain treatment presented a break-even quantity of 351.02 kg, and the improved clay granary with grain treatment presented a break-even quantity of 369.22 kg.

In Boukoumbé, the PICS bag presented a break-even quantity exceeding 100 kg. The PICS bag without grain treatment yielded 132.32 kg, while the metal silo with grain treatment yielded 946.72 kg (Table 4). The break-even quantity for the metal silo was approximately one ton, while the improved clay granary presented a break-even quantity of less than 500 kg. The metal silo without grain treatment yielded 932.62 kg, compared to 946.72 kg for the metal silo with grain treatment. The improved clay granary without grain treatment presented a break-even quantity of 346.30 kg, and the improved clay granary without treatment presented a break-even quantity of 317.41 kg.

#### 3.3.4. Analysis of the Sensitivity of the Benefit–Cost Ratio and of the Break-Even Quantity

Tables 5 and 6 present the results of the sensitivity analysis of the benefit–cost ratio and the break-even quantity of the treatments implemented in Savalou and Boukoumbé. On the one hand, we increased the fixed costs by 10% and decreased the selling price of maize by 30% and 40%. On the other hand, we increased the fixed costs by 10% and the selling price of maize by 30% and 40%. In the two (02) municipalities, the results showed that the break-even quantity was the most sensitive indicator to variations in the fixed costs of storing maize and the selling price of maize.

Rising fixed costs of 10% and a decrease in maize sales price implies a decrease in the benefit–cost ratio value, whatever the type of structure. The polypropylene bag and PICS bag without grain treatment had the highest benefit–cost ratio compared to other structures, with an increased fixed cost of approximately 10%, and a decrease in maize sales price by 30% and 40% (F = 0.95; *p* < 0.05). The same trends were observed following an increase in the maize sales price by 30% and 40%; however, the improved clay granary also had the highest benefit–cost ratio. In Savalou, the reduction of the selling price of maize by 40% (compared to the current selling price of maize) caused the polypropylene bag without grain treatment to no longer be profitable for maize storage for a break-even quantity of −1322.34 kg, given its statistically low value compared to that of other structures (*p* < 0.001) (Table 5). The result was the same for the metal silo without treatment, which became unprofitable following 30% and 40% reductions in the selling price of maize, with the break-even quantity changing from 166.06 to −22.40 kg. On the contrary, an increase in the selling price of maize by 30% or 40% caused the metal silo to be profitable for maize storage for break-even quantity.

In Boukoumbé, the metal silo with and without grain treatment constitutes the main storage and preservation technology, and the break-even quantity of this technology is very sensitive to variations in the selling price of maize. However, the storage of maize remained profitable, given its statistically high value compared to that of other structures (*p* < 0.001). Indeed, the break-even quantity increased from 150.63 to 198.40 kg for the storage of maize in the metal silo without grain treatment, with reductions in the selling price of maize of 30% and 40%, respectively (Table 6). For the metal silo with grain treatment, the break-even quantity increased from 147.60 to 181.46 kg and then to 235.60 kg (Table 6). On the contrary, a decrease in the break-even quantity was observed with regard to an increase in the selling price of maize. The same trends were observed in Saval.


*p* > F probabilities are indicated by symbols: ns = no significant differences; \*\* = significant differences at *p* < 0.05; \*\*\* = significant differences at *p* < 0.01. For each column, values withsame letter indicate no significant differences at 5%. Source: Experimentation data from 2015, 2016 and 2017 (− ctrol = without chemical conservation measure; + ctrol = with chemicalconservation measure).

 the

#### *Agriculture* **2021**, *11*, 32


*p* > F probabilities are indicated by symbols: ns = no significant differences; = significant differences at *p* < 0.05; = significant differences at *p* < 0.01. For each column, values with the same letter indicate no significant differences at 5%. Source: Experimentation data from 2015, 2016 and 2017 (− ctrol = without chemical conservation measure; + ctrol = with chemical conservation measure).

**Table 6.**

Sensitivity analysis of the benefit–cost

 ratio and the break-even

 quantity of the different treatments

implemented

 in

Boukoumbé.

#### **4. Discussion**

Regardless of municipality, the PICS bag recorded the lowest loss rate. The PICS bag with treatment recorded total losses of 9.42% (±4.64%), and the PICS bag without a chemical control recorded total losses of 11.71% (±2.78%) in Savalou. The PICS bag with grain treatment recorded total losses of 2.69% (±0.77%), and the PICS bag without chemical control recorded total losses of 7.71% (±1.74%) in Boukoumbé. Our findings agreed with results obtained by Poudel et al. [22], who evaluated the efficiency of maize storage and conservation structures in Central and Northern Benin and concluded that in Savalou, as in Boukoumbé, the PICS bag without grain treatment with Actellic® Super was more effective than the untreated polypropylene bag for reducing loss rates.

*Sitophilus zeamaïs* and *Tribolium castaneum* were the two main pests counted in stocks, and the better pest control technology was the PICS bag. Pests were more common in Savalou than in Boukoumbé. This may be because Savalou is a humid area, and Boukoumbé is a dry area. However, the assessment of pest levels compared to temperature or moisture was not studied.

The benefit–cost ratio of the PICS bag without a chemical conservation measure was the highest (7.89) in the Savalou region. Ndegwa et al. [23] found a similar result and observed that airtight bags (the PICS bag and the SuperGrain Bag) without preservatives exhibited the highest benefit–cost ratio of 1.6, with a loss rate of 3.9% over four months of storage in Kenya.

The benefit–cost ratio of the metal silo in Savalou was 5.86 without the chemical conservation measure and 4.99 with the chemical control. This ratio for the metal silo was 6.20 without the chemical protectant and 5.28 with the chemical protectant measure in Boukoumbé. Compared to the improved clay granary, the metal silo displayed the highest ratios regardless of region. The metal silo had a ratio of 4.99, compared to the improved clay granary without and with conservation measure, which presented benefit–cost ratios of 4.85 and 3.63 in Savalou, respectively, and 4.35 and 4.18, respectively, in Boukoumbé, and was more profitable. Our findings agreed with results obtained by Nduku et al. [24], who performed a comparative analysis of the metal silo with storage technologies in a traditional improved granary in Kenya. The highest ratios obtained for the metal silo and the improved traditional granary were 2.5 and 1.6, respectively. Similarly, the metal silo was profitable at a break-even quantity of 1000 kg, regardless of the level of variation of maize sales price at Boukoumbé. It was in this context that De Groote et al. [13] proposed assessing the cost per kilogram of grain stored for different capacities of metal silos to determine the type of metal silo that would be financially and economically profitable.

The untreated polypropylene bag had the highest benefit–cost ratio of 6.91 in the northern region. We observed that agroclimatic conditions influenced the efficiency and the profitability of storage technologies; however, our research did not address these aspects.

For both Central and Northern Benin, the improved clay granary with chemical conservation measure was more expensive than the reference technology (here, the polypropylene bag with the chemical control). Adégbola et al. [3] found a similar result and indicated that the improved clay granary was more expensive than the reference system (traditional granary with treatment using local products) in southern Benin.

#### **5. Conclusions**

To identify strategies that reduced postharvest losses of maize and improved maize storage, conservation technologies were introduced in central and northern Benin. The loss rates and financial profitability of these different storage and conservation technologies were assessed. The analysis showed that, in central and northern Benin, the PICS bag and the polypropylene bag recorded less storage losses and were more profitable than the improved and closed earth granary and the metal silo. Specifically, the PICS bag without treatment was more profitable in Savalou, and the polypropylene bag with treatment was more profitable in Boukoumbé. The PICS bag and the polypropylene bag had a low initial investment cost compared to the improved clay granary and the metal silo, which had a high initial investment cost. The metal silo was also found to be more efficient and profitable than the improved clay granary, but the initial investment for the metal silo was high, and it was profitable at a break-even quantity of 1000 kg. To facilitate the dissemination and adoption of the metal silo, especially by small producers, a reduction in import taxes on galvanized sheet metal, which is the raw material for manufacturing metal silos, may help reduce the cost. In addition, appropriations adapted to the storage of grains in these technologies will have to accompany their diffusion. The PICS bag and the polypropylene bag are plastic bags, the recycling of which takes time after use. Governments should take responsibility for reducing the import taxes on galvanized sheet metal to facilitate the distribution and use of the metal silo; however, storage in bags facilitates transportation but does not protect the environment.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/article/10 .3390/agriculture11010032/s1, Table S1: Monthly flow costs of storing one kilogram of maize in the polypropylene bag, Table S2: Monthly flow costs of storing one kilogram of maize in the PICS bags, Table S3: Monthly flow costs of storing one kilogram of maize in the Metal silo, Table S4: Monthly flow costs of storing one kilogram of maize in the Improved clay granary.

**Author Contributions:** Conceptualization, E.S.G., Y.P.A. and G.B.; methodology, E.S.G., Y.P.A., P.M.H., S.R.C.Z. and G.B.; software, E.S.G., P.M.H. and S.R.C.Z.; validation, E.S.G., Y.P.A., S.R.C.Z. and G.B.; formal analysis, E.S.G., P.M.H. and S.R.C.Z.; investigation, E.S.G., P.M.H. and S.R.C.Z.; resources, E.S.G.; data curation, E.S.G., Y.P.A., P.M.H. and S.R.C.Z.; writing—original draft preparation, E.S.G., P.M.H., S.R.C.Z. and G.B.; writing—review and editing, E.S.G., Y.P.A., P.M.H., S.R.C.Z. and G.B.; visualization, E.S.G., Y.P.A., P.M.H., S.R.C.Z. and G.B.; supervision, E.S.G., Y.P.A. and G.B.; project administration, E.S.G., Y.P.A. and G.B.; funding acquisition, E.S.G. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Swiss Cooperation and HELVETAS Swiss Intercooperation.

**Data Availability Statement:** Data sharing not applicable. No new data were created or analyzed in this study. Data sharing is not applicable to this article.

**Acknowledgments:** We acknowledge the Swiss Cooperation and HELVETAS Swiss Intercooperation for their funding and scientific contribution to the implementation of the experimental device. We also thank the National Agricultural Research Institute of Benin (INRAB), the Food and Agricultural Technology Program (PTAA) and the experimental producers from the communes of Savalou and Boukoumbé that mobilized in the context of this research. We also thank Centre International de Recherches et de Formations en Sciences Sociales (CIRFoSS) for data collection, processing and contribution to data analysis.

**Conflicts of Interest:** The authors declare no conflict of interest.
