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La plataforma permanente Atomium Culture reúne a las universidades, periódicos y empresas más prestigiosos de Europa para promover el flujo del conocimiento más allá de fronteras, entre sectores y hacia el público en general.

Eco-Friendly Residues Could Help Plants and Reduce Dietary Deficiencies

Por: | 04 de marzo de 2014

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By Lourdes Hernández Apaolaza, Universidad Autonoma de Madrid (UAM)

Image: Experimental setup, with the results for zinc shown. Zinc lignosulfonates showed a better result than the corresponding inorganic salt.

Dietary iron deficiency is the most common and widespread nutritional disorder in the world. The World Health Organization estimates that nearly 3.7 billion people are iron deficient, with 2 billion of these so severely deficient in iron that they can be described as being anemic. In addition, 35% of all children in the world between newborns and 5-year-olds suffer from zinc or iron deficiencies, 250 million suffer from vitamin A deficiency, and 260 million suffer from iodine or selenium deficiencies. Childhood anemia and dietary deficiencies can lead to poor development, resulting in significant physical and learning disabilities.

The root of the challenge may be in how farmers treat their crops. Iron and zinc malnutrition in humans is derived from deficiencies of these elements in soils and foods. The soil–plant system truly forms the basis of the “food chain”, in which the nutrient cycling results in a sustainable flow of nutrients. The uptake of iron and zinc by the plant and its transport to the edible parts can actually be increased by suitable fertilizer applications. Traditionally, inorganic salts-based fertilizers are applied, which often end up fixed to a large extent on the soil, thus, the iron and zinc are not available for the plants. The addition of synthetic fertilizers (chelates) is a good solution, but these products are expensive and may cause environmental problems. Yet another alternative could be the use of industrial residues.

Still, industrial wastes are under suspicion: are all of them toxic? Do they contain toxic elements? Let us look at the issue more closely.

First, how do we know when plants have a shortage of iron or zinc? Most of the time, it is quite obvious. When there is not enough iron or zinc, their leaves turn to a yellow color and the fruit or grain production decreases considerably. We can compare these symptoms with the human symptoms of anemia, a common ailment. When we have anemia, we go to the doctor and he/she prescribes to us a specific diet and sometimes a medicine to treat the deficiency. In any case, the doctor does not advise us to eat iron nails or iron balls, because it is impossible for us to absorb their iron. When plants are “anemic”, the plant scientist “doctor” analyzes them and if the diagnosis is chlorosis (plant anemia), he prescribes iron or zinc in a chemical form that plants can absorb and use to grow. But it turns out, there is a eco-friendly solution that comes from plants themselves.

Paper production requires tons of wood and also produces tons of byproducts or residues. One of these residues are lignosulfonates. In general, 1,000 kg of wood pulp produces between 330 and 540 kg of lignosulfonate residue. But these compounds have the ability to bind plant nutrients, such as iron or zinc. Moreover, this residue is not toxic because its main constituent is lignin, which is completely biodegradable, much like the forest branches that fall each autumn.

We still need to know if lignosulfonates bind these nutrients in such way that allows them to be available to the plants (not bound to the soil). Plants have the answers! We conducted different experiments with young cucumber, wheat, corn and soybean plants by applying iron and zinc lignosulfonates either to the leaves or to the plant food solution (water-based). The iron and zinc lignosulfonates showed a better result than the corresponding inorganic salt, but worse than the synthetic fertilizer (see photograph). The lignosulfonate amounts applied in our experiments were actually quite low and that could be the main reason for this. However, we are still convinced that their biodegradability remains a great advantage for the lignosulfonates.

By binding stable iron and zinc tracers (57Fe and 67Zn) to the lignosulfonate, we were able to track the nutrients iron and zinc through the plant and follow their distribution inside it, without altering the original experiment. With this technique, our research team tested several hypotheses: first, that the nutrients get inside the plant when they are applied with lignosulfonates; second, exactly how much of each metal gets to the plant; and third, the precise locations of the applied metal inside the plant.

Our research shows how a simple and efficient use of an otherwise “undesirable” industrial residue could potentially change the way farmers treat their crops in the future and even have a positive effect on alleviating dietary deficiency. Further research is required to complete our understanding and, ultimately, to scale up the process effectively.


Lourdes Hernández Apaolaza
Universidad Autonoma de Madrid (UAM)

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