AG R OC HEM I CAL S
Micronutrients – Serving an Agricultural Revolution A quiet revolution is taking place in agriculture with the rise in hydroponics, or soilless culture, where all plant nutrients are supplied in a liquid solution. Marcel Bugter, AkzoNobel Market Development Manager, explains some of the chemistry involved.
ydroponics is already widely used in commercial greenhouses for growing crops such as tomatoes, cucumbers, strawberries and roses, but is also at the forefront of the social trend towards urban gardens and urban farming. Plants require some 15 essential elements to grow. The three main ones –oxygen, carbon and hydrogen – are absorbed from the atmosphere, while the others are taken up through the roots. Six of those –iron, zinc, manganese, copper, boron and molybdenum – are referred to as trace elements, since they are required only in small quantities and fertilizers based solely on these trace elements are called micronutrients. The use of a soilless culture is made possible by the use of chelating agents, claw-like organic molecular structures that can tightly ‘grip’ metal ions. Metal chelates are stable and readily soluble in water and do not react with the other compounds used in agriculture, such as phosphates, and protect the metal ion itself from reacting. Moreover, they are readily absorbed by plants, making them the method of choice for delivering trace elements to plants in a hydroponic culture. Most commercial chelates are aminocarboxylates such as EDTA (ethylenediamine tetraacetic acid), which contain polydentate (multiply bonded) ligands that form bonds with metal ions. Chelates have widespread applications beyond agriculture, including animal feeds and in human nutrition,
medical uses such as detoxification, and industrial applications including catalysis and water softening. In a hydroponic environment, micronutrients are delivered as chelate micronutrients. The chelated iron is a form that keeps iron in solution and prevents it from precipitation. Once precipitated, for example as the insoluble iron hydroxide, the essential element iron will not be available for uptake by plants. However, there are different chelates and the choosing the correct one is critical to ensure the right delivery of micronutrients to the crop. This is particularly true for iron chelates, when the choice of which chelate a grower should use depends on the pH of the particular growing medium. When certain pH values are exceeded, other metals, like calcium and copper, replace the iron ion bound to the chelate. Iron ions that are displaced from the chelate are not soluble at higher pH levels and consequently precipitate, mostly as iron hydroxides, which is a form that plants cannot use. To help with the selection process, AkzoNobel recently joined with companies Yara, SQM, Eurofins Agro, NMI and Geerten van der Lugt to jointly publish a manual to advise growers on how to get the right micronutrient solution. It covers the key varieties such as fruiting and leafy vegetables, cut flower and pot plant crops grown in hydroponic systems in commercial greenhouses and, increasingly, in urban agriculture.
The need for chelated micronutrients is expected to rise rapidly with the growth in hydroponics. Experts say the value of the global hydroponics market could increase by close to 50% to over $27 billion by 2020. One of the major growth drivers for the industry is the documented higher yield in comparison to traditional agricultural techniques. Along with profit farming, growing consumption of exotic, salad crops and increasing need for global food security will drive market growth. Growth will also be driven by urban agriculture, as spaces in cities are turned over to provide green spaces and for crop production. The power of urban gardens to revitalize cities and make people’s lives more livable and inspiring was recently showcased by AkzoNobel at the Habitat III Conference on Housing and Sustainable Urban Development in Quito, Ecuador. As part of the event’s Habitat III Village, a vertical garden was created to help transform a bleak expanse of concrete into a colorful and more attractive space using a hydroponic system.
CONTACT Marcel Bugter AkzoNobel Market Development Manager Akzo Nobel N.V. Amsterdam The Netherlands www.akzonobel.com/micronutrients
Creating a vertical garden, using a hydroponic system
36 Speciality Chemicals Magazine 37.01 February 2017