1. Introduction
Iodine deficiency disorders (IDDs) are a public health concern and affect approximately 2 billion people globally [
1]. Iodine is an important trace element required for the proper functioning of the thyroid gland. Its deficiency, IDDs, which causes devastating health outcomes, has been primarily managed through industrial iodized table salt [
2], though many communities continue to be affected by IDDs. Therefore, complementary and sustainable approaches to prevent IDDs have been recommended.
Biofortification, the process of enriching the micronutrient content of food crops during production [
3], is considered a key and effective strategy to increase dietary intake of iodine [
1,
4]. Iodine biofortification can either be achieved through an agronomic pathway (direct agro-chemical application of iodine to crop leaves or to the soil) or a (genetic) breeding approach [
1]. Although the latter seems promising, is less costly, and is more sustainable in the long run, as planting seed material remains viable for many seasons [
5,
6], the initial investments are high and selecting target genes as well as testing for genotype and environmental interactions takes a long time [
1,
7]. Hence, agronomic biofortification presents a practical and feasible alternative capable of enhancing the iodine content of staple foods in the short run. Previous studies have demonstrated the efficacy of many food crops to absorb and accumulate iodine, applied as fertilizer [
4,
8,
9,
10,
11], despite also being considered relatively expensive to routinely buy and apply in rural contexts [
7,
12]. For example, agronomic biofortification with iron (Fe) and zinc (Zn) was found to cost between USD 376–942 and USD 311–1146 per disability-adjusted life year (DALY) saved, respectively, in China [
7], whereas Zn agronomic biofortification cost an estimated USD 461–619 per DALY saved in Vietnam [
13] and USD 226–574 in China [
14]. Nonetheless, agronomic biofortification has an impact on health outcomes and is the most practical approach to increase the iodine content of food crops. In addition to production costs incurred, it is important to also quantify the benefits, more so in economic terms, of the biofortification strategy to establish potential trade-offs that can justify adoption among farmers. Economic incentives potentially influence the adoption of new technologies [
15] and the level of economic gain from iodine biofortification is likely to vary among producers. Thus, an assessment of the costs and benefits of agronomic biofortification should account for the production practices prevalent in a given context.
Cost–benefit analysis (CBA) is used to evaluate the economic feasibility of projects so as to guide investment decisions [
16,
17]. When used in the agri-food sector [
18], costs generally refer to the total costs incurred during the production period (e.g., field preparation, transport, agro-chemical, harvest, etc.), whereas benefits reflect the revenue received by selling the produce [
16,
19,
20]. CBA has also been applied to analyze the economic feasibility of GM crop cultivation [
15] and to support the release of GM forest crops (Kazana, et al.) [
21]. The previous focus on cost-effectiveness, largely to assess the potential health impact of conventionally bred [
22] and genetically engineered [
23] biofortified crops at the societal level, has masked the application of CBA at the farm level. Therefore, this study aimed to fill this research gap by investigating the economic feasibility of iodine agronomic biofortification of vegetables at the farm level in Northern Uganda. In this context, additional costs incurred in novel food production are often covered by agents in production or passed to the consumers [
24]. Thus, the real costs incurred in introducing iodine fertilizer in crop production will most likely be covered by the producers and/or consumers. However, as iodine is a non-essential element for plant growth [
25], its application may have no significant effect on yield or other agronomic outcomes, e.g., stress tolerance, which could be a reason for adoption at the farm level [
26]. In other words, farmers may not have an economic incentive to introduce iodine fertilizer into their production, unless they positively perceive possibilities of higher revenues. Therefore, the feasibility of agronomic iodine biofortification would largely hinge on higher premiums paid by consumers for iodine-biofortified foods, as previously indicated [
18,
24]. Therefore, we examined consumers’ WTP as an indicator of the benefits of agronomically producing iodine-biofortified cabbage and cowpea.
4. Discussion
This study carried out a CBA for iodine biofortification versus the current production of cabbage and cowpea at a farmer field setting in Northern Uganda. Premium prices were used to estimate the potential revenues that farmers can achieve by producing iodine-biofortified vegetables. Previously, stakeholders in the country have been shown to hold a positive perception on agronomic iodine biofortification [
28] and to have a high willingness to include iodine-biofortified foods in their family and school diet [
39]. The results confirmed the positive perception and preference of consumers towards the consumption of iodine-biofortified foods produced in Uganda. The higher premiums that consumers are willing to pay for iodine-biofortified products could help cover the extra costs that farmers will incur when purchasing iodine-rich fertilizers. In a previous study, which also applied consumer WTP in CBA, Kawata and Watanabe [
24] found that the consumers’ premium was enough to cover the extra associated cost of producing
Campylobacter-reduced chicken, compared to normal chicken production. A similar observation was made in the study of Pappalardo et al. [
18], in which consumers’ additional WTP was sufficient to cover the cost of high heat treatment in pasta production. This implies that the extra cost of iodine enrichment can be adequately covered from the sale of products, and this can act as an incentive to motivate farmers to adopt iodine biofortification. It should, however, be noted that crop biofortification is a health policy intervention targeting the poor and vulnerable, who often have micronutrient deficits. Thus, farmers should be supported to further lower production costs and not pass on the price burden to consumers, as indicated in our findings.
4.1. Benefit–Cost Ratios
The BCRs of 3.13 and 5.69 for the production of iodine biofortified cabbage and cowpea, respectively, indicate that this strategy would be economically viable in Northern Uganda. Comparable results were obtained in previous studies by Abdul Rahman et al. [
40] and Singhal et al. [
41], who carried out a benefit–cost analysis of using nitrogen fertilizers and water-soluble fertilizer in cowpea production in West Africa and India, and obtained BCRs of 2.7–4.6 and 3.4, respectively. The BCR for cabbage production in the current study is also comparable to those obtained by Vidogbéna et al. [
29] in their CBA on the use of insect nets to control pests in cabbage production. However, the BCR for producing cabbage using iodine fertilizer obtained in the current study is much lower than those obtained in the study by Amoabeng et al. [
35], who investigated the economic viability of using botanical insecticides to control cabbage pests in Ghana. They obtained BCRs as high as 1:29 and 1:25. The difference between their results and ours could technically be related to the fact that their study considered only the cost related to plant protection (insecticide use), whereas the benefits referred to the income from the total cabbage yield. We analyzed the total cost of producing cabbage by applying iodine fertilizer (total production cost), increasing the total cost and lowering the BCR as compared to those obtained in the aforementioned study. This is particularly important, as it illustrates the economic effect of the intervention (iodine biofortification) on the overall production, as also reported in the studies by Amulen et al. [
19] and Vidogbéna et al. [
29].
When comparing the current production of cabbage and cowpea in Northern Uganda to the projected production with iodine fertilizer, the latter would be more economically viable compared to the current production. This difference is a result of differences in costs and revenues that would be earned from each production practice. For instance, for an acre of cabbage production, on average, the total cost of current production is USD 297. This cost would increase to USD 367 if farmers were to biofortify their production. This difference was caused by the additional iodine fertilizer cost and the associated labor cost. However, due to consumers’ higher WTP for iodine-biofortified cabbage compared to non-biofortified products, the total revenue earned from iodine biofortification (USD 1130) would be higher than that from current production (USD 811), leading to a more economically viable production, with iodine agronomic biofortification, than the current cabbage production. The same explanation applies to the differences in BCR for cowpea production with and without iodine fertilization. The implication of this finding is that the economic viability of iodine biofortification will not only depend on farmers’ production capabilities (e.g., economy of scale), but also largely on how much more consumers are willing to pay for the biofortified foods compared to the field substitutes.
The BCR for iodine agronomic biofortification is positively predicted by the level of household income and crop type, with cowpea appearing to be more economically viable compared to cabbage. The difference between the two crops can be explained by the difference in production cost. Cabbage production involves sowing and maintaining the crop in the nursery bed for some weeks before transplanting to the main field, whereas cowpea seeds are sown directly in the main field, hence the lower costs (see
Table 4 and
Table 5 for total costs). Another explanation for this difference is that iodine-biofortified cowpea would generate a higher premium (additional WTP) compared to biofortified cabbage (see results in
Table 3). This would result in a higher benefit and, with a lower overall cost of cowpea production, a better BCR compared to cabbage production. However, this result may not apply to all situations. One must separate the effect of the study location. For instance, in Northern Uganda, cowpea is eaten more often (and by more households/people) than cabbage, which could explain the higher willingness to pay (premium) for cowpea compared to cabbage, something that might differ elsewhere. Nevertheless, these results suit the target of biofortification, which is to improve the micronutrient content of food crops that are already liked and eaten in big quantities by poor people, especially in developing countries [
5]. The results confirm the previous assertion that the societal cost-effectiveness of biofortification depends on the micronutrient–crop combination targeted [
42,
43]. The positive influence of household income on BCR could reflect the ability of high-income households to purchase iodine fertilizers and meet the associated labor cost. A lack of capacity to pay for farm-level innovations, including inputs such as fertilizer, has been cited as one of the causes of low uptake of agricultural innovations in developing countries. In fact, it has been proven that as income increases, farmers are willing to pay more for farm innovations [
44,
45]. The positive effect of household income on BCR could therefore reflect the ability of high-income farming households to invest more in iodine biofortification than low-income households, hence the higher BCR.
4.2. Differences in BCR among Farmers
The variation among sampled farmers, in terms of the BCR, indicates that some farmers would benefit from iodine agronomic biofortification, whereas others currently would not. Even among those who would benefit, the level of economic gains would vary. This is expected due to differences in managerial and agronomic capabilities among farmers, as also noted by Flannery et al. [
15]. Vidogbéna et al. [
29] suggested that the difference in BCR among cabbage farmers was attributable to differences in knowledge and farming practices. Our CBA was based on the prevailing farming practices at the time of the study, which are expected to vary among farmers. In our study, differences in BCR could be related to experience in fertilizer use, as farmers who have previously applied chemical fertilizer would likely benefit more from iodine fertilizer application (agronomic biofortification) than those who have no such experience, as shown in the results.
Although the sensitivity analysis results showed that a substantial proportion of farmers could produce profitably after subsidization of the costs involved in introducing iodine fertilizer, some farmers simply have a poor cost structure that would prevent them from producing profitably. For instance, the proportion of farmers with a BCR above 1 was levelled at 96% after subsidizing 20% of the cost of iodine biofortification of cowpea (see
Table 7), suggesting that the remaining 4% of the farmers have a very low cost structure, perhaps because they have a low use of certain inputs like chemical fertilizers. With the introduction of iodine fertilizer and the associated costs, their costs are escalated, resulting in non-profitable production. Vidogbéna et al. [
29] found out that the labor cost for pesticide use was correlated with the frequency of pesticide use, which differed among farmers and provides the explanation for the variation among farmers. According to Katungi et al. [
46], only 30% of the farmers in their sample incurred the cost of plant protection, which would lead to differences in profitability among farmers. In summary, the variation in BCR among farmers can be attributed to the differences in agronomic and management practices. Thus, the promotion of iodine agronomic biofortification should be careful of the heterogeneity among farmers, including the gap in experience with fertilizer application.
5. Conclusions
The study carried out a CBA of iodine agronomic biofortification in a farmer field setting in Northern Uganda. The results revealed that iodine agronomic biofortification would be more economically viable than the current production practice. The viability, however, depends on crop type. Considering the two crops studied, cowpea was seen to be a more profitable crop for iodine biofortification than cabbage, mainly because of the lower production cost but also the relatively higher premium that consumers were willing to pay for iodine-biofortified cowpea compared to cabbage. This is important for guiding the choice of crops to biofortify, which should be well liked and consumed in high quantities in a particular location. It will also be crucial to promote the production of iodine-biofortified staples. However, one of the most important findings of our study is that a substantial proportion of smallholder farmers in Northern Uganda would implement iodine agronomic biofortification at BCRs below 1 (non-profitable range), according to their current practices. This is considered an important finding, as the majority of cost–benefit studies have reported only average values, which are largely affected by outliers. Knowing this proportion helps guide the selection of support for smallholder farmers to improve the nutrient density of food crops, which would eventually improve micronutrient intake and prevent deficiencies. For instance, we carried out a sensitivity analysis to predict the proportion of farmers who would produce profitably if the cost of iodine fertilizer were to be subsidized at varying levels for smallholders. Subsidies could also be established to cover the premium value of biofortified crops in order to avoid passing additional costs to consumers.
The study is considered the first to analyze, in monetary terms, the costs and benefits of iodine biofortification at the farm level, with a focus on smallholders from a developing country as the key target group of biofortification. In addition, it points to the need to carefully choose crops when planning iodine biofortification in a particular location. Finally, the study advances a step further in the literature by integrating consumers’ WTP into an ex-ante cost–benefit study on farmers’ potential adoption of iodine biofortification.