Foliar fertilizer shows promise in reducing zinc deficiency

Yield can no longer be considered only in terms of volumes and weights

While many people are focused on the fight to end hunger, Professor Ismail Cakmak of Istanbul’s Sabanci University is focused on the fight to end hidden hunger.

“Hunger is a lack of food and that is related to food security,” Cakmak told participants during a special seminar at the University of Manitoba this summer. “But hidden hunger means lack of the vitamins and minerals in a given food. So we have to distinguish food security from nutrition security. In the past we rarely talked about nutrition security, we talked a lot about food security, but not much about the nutrient security.”

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While the so-called Green Revolution did a great deal to increase yields, the professor of molecular biology, genetics and bioengineering said the push for bigger harvests also had unintended consequences. For one, it diminished the amount of nutrients in staple grain crops, such as wheat and corn.

“During the Green Revolution we focus always on the new genotypes having high capacity to produce more yield, make more grain, and more starch in the grain to increase the size to mitigate the hunger problem, but during that time we didn’t pay sufficient attention to the nutritional value of the products that they produced,” Cakmak said.

In wealthy, developed countries where vast quantities of animal protein are consumed, micronutrient deficiency isn’t a problem, he explained. But in poor, developing nations where people eat little animal protein, diets are unable to compensate for the low level of micronutrients found in wheat, corn and rice.

“They are eating a lot of cereals, so that after a certain amount of time, deficiency problems with micronutrients develop,” said the professor. “Because in the developing world, due to socio-economic reasons, people eat a lot of cereal-based foods.”

In some regions of the world, 75 per cent of people’s daily caloric intake comes from cereal crops, he said.

While developing new cultivars better able uptake micronutrients like zinc, iodine and iron is one possible solution, Cakmak said that plant breeding is a slow, long-term process that won’t offer relief for decades. Fortification could provide very short-term relief to hidden hunger, but would be too expensive to maintain.

“Tell me, how can we implement such a solution in the rural areas of India? You cannot,” he said. “Supplementation, fortification can be a good solution, but it is a short-term solution.

Even with better cereal varieties on hand, mirconutrient-deficient soils could still defeat the best efforts of plant breeders, he added. About 40 per cent of the world’s agriculture soils have some type of nutrient deficiency, he said.

“Zinc deficiency, iron deficiency are very common problems in agricultural soil,” he said. “Today nearly 50 per cent of cereal soils have zinc deficiency… now imagine that you are growing these cereals on such deficient soils, you further reduce the plant’s ability to take up zinc.”

“There is also close overlap between human zinc deficiency and soil zinc deficiency, and when you have zinc deficiency problems in the soil, then you have another problem, an agronomic problem, the seed has poor growth,” he added.

But Cakmak said there is a third option in the works, one that would see farmers apply micronutrients as a foliar fertilizer.

“When we apply zinc not to soil, but to foliage, to leaves, shoots, you improve (wheat’s) zinc concentration by 85 per cent, sometimes 100 per cent,” said the professor, adding the new and unpublished findings come from his work with the HarvestZinc Fertilizer Project.

Part of the HarvestPlus Pro­gram, which is largely funded by the Bill and Melinda Gates Foundation, HarvestZinc launched in 2008. Now in its third phase, researchers are testing newly developed zinc- and iodine-containing fertilizers on wheat, rice and corn in China, India, Thailand, Pakistan, South Africa and Brazil.

“So this biofortification, this enrichment of the food crops with micronutrients is a really hot topic today, because up to five per cent of gross domestic production is lost just because of micronutrient deficiency in some countries, that’s huge,” said Cakmak, adding child mortality is also strongly linked to hidden hunger.

However, while wheat responded exceptionally well to foliar zinc and iodine applications, rice only saw zinc levels increase by about 20 per cent and corn saw no substantial improvement.

What most interests Cakmak is not just that foliar zinc applications increase zinc in wheat, but that it specifically increases zinc levels in wheat endosperm — the most widely consumed portion of the grain.

“When you spray zinc after flowering time… there is a fantastic, very nice increase. You can get the zinc in the endosperm part up to 50 ppm. This is a very good increase, very nice in terms of human health,” he said, noting that humans require zinc to process more than 3,000 different types of protein.

“In the end, agriculture will be the solution to this problem,” he said. “Medicine and agriculture must work together… but the only real solution for micronutrient deficiency globally, has to come from the agricultural sector.”

About the author

Reporter

Shannon VanRaes is a journalist and photojournalist at the Manitoba Co-operator. She also writes a weekly urban affairs column for Metro Winnipeg, and has previously reported for the Winnipeg Sun, Outwords Magazine and the Portage Daily Graphic.

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