Agronomic zinc biofortification: A sustainable strategy to enhance nutritional quality of rice in Madagascar

Zinc biofortification offers a sustainable and effective solution to combat micronutrient deficiencies by increasing the zinc content in staple crops. Biofortification can be achieved through conventional breeding, modern biotechnology, and agronomic practices. Agronomic biofortification, or ferti-fortification, emphasizes the strategic use of zinc fertilizers in soil and crop management to enrich the crop produce.

Currently, many Malagasy people suffer from zinc deficiency, a significant public health concern associated with the high consumption of cereals, particularly rice. In Madagascar, rice is the most important staple food with an annual per capita consumption of 143 kg (FAOSTAT, 2021). Micronutrients rich foods such as fruit and vegetables are often too expensive for the common people to afford. Among the relatively affordable options, rice holds the top priority due to its central role in the Malagasy diet. However, white rice, the most consumed, contains only about 13.7 mg of zinc per kilogram of grain, which falls short of the daily zinc requirement of approximately 11 mg for adults.  Addressing zinc deficiency through ferti-fortification of rice offers an effective and immediate solution. This approach integrates the application of zinc-enriched fertilizers into rice farming practices, offering a practical and scalable solution for the country’s predominantly smallholder farming systems.

Breeding efforts have shown promising results, including the development of the zinc-biofortified rice variety “Mavitrika”. This variety is the outcome of a collaborative work by AfricaRice, the Japan International Research Center for Agricultural Sciences (JIRCAS), the University of Bonn, and FOFIFA in Madagascar (https://www.africarice.org/post/high-zinc-rice-for-marginal-soils-in-madagascar). To accelerate efforts to tackle the Zn deficiency problem in the country, we added an agronomic biofortification approach. The zinc enrichment through the management of zinc fertilizers could be expected to improve yield as well as Zn concentration in grains. This study evaluates the interaction effects of genotype, environment, and zinc management practices on grain yield and grain zinc concentration under irrigated lowland conditions. Additionally, we evaluated the interaction effects of parboiling with the treatments on the zinc concentration of biofortified grains since our previous studies showed parboiling influenced micronutrient concentrations of brown/milled rice.

Methodology

In 2023, adaptability and performance tests were conducted on six zinc-biofortified rice lines along with red rice and local check varieties. Two biofortified lines and one red rice variety were selected for their superior agronomic performance and high zinc content. These varieties were used in an agronomic biofortification trial in Ankilizato, Menabe region of Madagascar, to evaluate the interaction effects of genotype, environment, and zinc fertilizer management on grain yield and zinc concentration.

The varieties tested included: local check variety (Sebota70 “V0”), red rice variety (FOFIFA195 “V1”) and two biofortified lines (BF19AR001 “V2” and BF19AR009 “V3”). Four zinc application methods were evaluated: No zinc application (Z0), foliar application (Z1), Soil application (Z2), combined foliar and soil application (Z3)

Preliminary results

The agronomic biofortification trial was conducted across two seasons—wet (January to May, 2024) and dry (July to November, 2024). Preliminary results revealed:

• Yield variability: Grain yields varied by genotype and season. Dry season (DS) yields were higher compared to wet season (WS) yields. The local variety achieved the highest yield, followed by the two biofortified lines, while the red rice variety had the lowest yield.

• Zinc application effects: The impact of zinc treatments differed by variety and season, highlighting the complex interactions between genetic and environmental factors.

Figure 1: Yield response of different genotypes to Zn treatments across seasons in Ankilizato –Madagascar

Similar experiments are ongoing in Senegal and Cote d’Ivoire.

The grain analysis is being conducted to measure zinc, iron and phytate contents in brown rice, milled rice, and parboiled rice, to assess whether parboiling enhances zinc content in biofortified grains. This additional process could offer a complementary method to improve zinc nutrition.

Future work

The trials will be continued through 2025 to validate the findings from the first year and further refine the strategies for agronomic zinc biofortification. This research aims to establish sustainable practices that not only boost the zinc content of rice but also support the livelihoods of smallholder farmers and address micronutrient deficiencies in Madagascar.

Photo: Experimental rice fields for agronomic zinc biofortification in Madagascar, Dry season 2024

Authors: Andriatsiorimanana Aina, Senthilkumar Kalimuthu

Address: Africa Rice Center (AfricaRice), Madagascar

Supporting One CGIAR initiative: This study was supported by the Excellence in Agronomy for Sustainable Intensification and Climate Change Adaptation Initiative