Keywords: Seed quality, Seed zinc, Turkey, Zinc fertilisers, Zinc deficiency, Wheat.
Zinc (Zn) deficiency in soils and crop plants is a common problem in cereal-growing areas, especially on calcareous soils. About half of the cereal-cultivated soils are Zn-deficient leading to severe decreases in crop production and low levels of Zn in grain. Zinc is also essential for humans playing critically important roles in disease resistance and in early childhood development. Often the areas with severely Zn deficient soils are also the regions where zinc deficiency in humans is most widespread.
Historically, wheat grown in Central Anatolia in Turkey was low yielding, but the reason was unclear. Before the 1990/1991 cropping season there was no scientific evidence that the low yields and wheat leaf disease symptoms (such as chlorosis and necrosis) observed were caused by Zn deficiency. At that time, several factors were discussed as possible reasons for the unknown disorder including drought stress, pathogenic infections, boron (B) toxicity and micronutrient deficiency. To identify the underlying cause for the symptoms and the low yield, in 1991/1992 a field experiment was conducted to investigate a lack of micronutrients as being a possible cause of the problem. The results showed that only in the case of Zn application was there an impressive increase in growth and yield of wheat and barley. Based on these initial observations, a multi-institutional, long-term project on Zn deficiency in crop production in Central Anatolia was set up and submitted to NATO-Science for Stability (SFS) Programme in 1992, and the project was approved in 1993.
The project yielded a large volume of valuable scientific data and information on the importance of zinc deficiency in wheat production in Central Anatolia. The results were very rapidly shared with the scientific community, industrial organisations, research institutions and especially farmers. There were spectacular increases in grain yield from using Zn fertilisers in different locations within Anatolia. In certain areas with very low yield (0.25 t/ha), Zn application enhanced grain yield by a factor 6 to 8 where the total amount of soil Zn was fairly high, between 40 to 80 mg/kg, but the level of plant available Zn was extremely low (DTPA-Zn: around 0.1 mg/kg soil).
Such impressive increases in plant growth and grain yield evoked a growing interest in the project findings among farmers and the fertiliser industry, and in 1995 production of Zn-containing compound fertilisers began. The reaction of farmers to Zn-containing NP or NPK fertilisers was so positive that in the following years increasing amount of Zn-containing fertilisers were produced and applied in Central Anatolia. Today, 10 years after the Zn deficiency problem was first diagnosed as a critical problem for wheat production in Central Anatolia, the total amount of Zn-containing compound fertilisers applied in Turkey is at a record level of 300,000 tonnes per annum. Ministry of Agriculture estimates put the annual economic benefits from the Zn fertiliser application at 100 million USD.
Not only have Zn fertilisers improved cereal productivity and farmers profits, but also the use of Zn fertilisers, by enriching the Zn content in grain, offers improvement to the health and productivity of large numbers of Turkish people who consume too little Zn from their diets. Applying Zn to wheat was effective in increasing grain Zn concentration by approximately 2-fold. Providing Zn-dense grain to the poor in Turkey should lead to improvements in their health, productivity, and mental development and in their livelihoods. This agricultural project should be looked on as a model for other nations to follow that face Zn deficiencies within their populations and crop production.
Ismail Cakmak, Sabanci University, Faculty of Engineering and Natural Sciences, Istanbul, Turkey.
26 pages, 5 Figures, 9 Tables, 61 References.