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Stakeholder workshop micronutrient management

By Huig Bergsma
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In April 2016 the project member Huig Bergsma from BodemBergsma participated in the stakeholder workshop “Micronutrient management for improving harvests, farmers’ incomes, human nutrition, and the environment” organized by the Food & Business Knowledge Platform at Centraal Museum in Utrecht. He wrote the following blog post, with the contribution of Tamara Jonkman.

Speakers

  • Coosje Hoogendoorn, KIT, facilitator of the workshop
  • Prem Bindraban, Virtual Fertilizer Research Center
  • Saskia Osendarp, Micronutrient Initiative
  • Shamie Zingore, International Plant Nutrition Institute, Nairobi
  • Wijnand van IJssel, Ministry of Foreign Affairs
  • Marc van Oers, Van Iperen International
  • Peter van Erp,SoilCares
  • Ken Giller, Wageningen UR
  • Inge Brouwer, Wageningen UR

Many are aware of the importance of Nitrogen (N), Phosphorus (P) and Potassium (K), as well as organic matter, for the growing of healthy crops. Focus on these has led to a neglect of micronutrients and how these may play a limiting role in yield increase, and that growing crops deficient of micronutrients can contribute to hidden hunger. Hidden hunger can be problematic as it can lead to health problems and makes people vulnerable to diseases such as measles and malaria1 2.

Nutrients needed for plant growth, outside of Hydrogen (H), Oxygen (O) and Carbon (C), can be divided along three categories based on the amount of nutrient that a plant needs for healthy development: macronutrients, secondary nutrients and micronutrients. However, just because plants requires less of a micronutrient, such as Zinc (Zn), than it requires Nitrogen, doesn’t mean that this nutrient is less important for plant development.

Macronutrients: Nitrogen (N), Phosphorus (P), Potassium (P)

Secondary nutrients: Sulfur (S), Magnesium (Mg), Calcium (Ca)

Micronutrients: Boron (B), Chlorine (Cl), Manganese (Mn), Iron (Fe), Nickel (Ni), Copper (Cu), Zinc (Zn), Molybdenum (Mo), Selenium (Se)

By amending soil micronutrient deficiencies, problems regarding micronutrient-poor crops could be overcome, but problems regarding these deficiencies are complex. They have very likely been caused by the focus on breeding high yield/low nutrient intake cultivars, the use of NPK fertilizers itself (P can inhibit the uptake of base metals) and several other soil degradation factors. In most cases Zn, Fe and Se turn out to be the problematic nutrients when dealing with depleted soils. Se being more relevant for human intake than for plants. Application of Zn is often successful and possible, application of Fe meets many problems.

Some of these micronutrients can cause problems when applied directly to the soil and it would be best to separate these antagonists from the other amendments by applying them as a foliar spray and a soil fertilizer.  Another possibility is the use of chelates; some nutrients, such as Cu and Fe, oxidize or precipitate quickly; in a chelate the nutrient is bound to a ligand (organic molecule) which protects it from these processes. These solutions are however costly, time consuming and, like the success of NPK application, also related to soil quality. For example, Ferralsols (deeply weathered soils of the humid tropics) are more responsive to treatment than Granitic soils (deeply weathered, sandy and infertile soils) (Shamie Zingore, Nairobi). In some cases the application of compost turned out to be more effective than the use of NPK fertilizers.

One of the limitations in properly addressing micronutrient deficiency is the lack of information regarding the mechanisms and processes involved in their presence, availability and uptake by plants. This is also caused by the difficulty of reliably measuring micronutrients with classical extraction methods; the use of an XRF (X-ray fluorescence device) has been suggested in order to measure micronutrients in a more reliably. A mobile lab was developed by SoilCares (Peter van Erp) which is able to analyse micronutrients (XRF), pH, N, P,K (NIR) and organic matter. Four of these mobile labs have already been sold in Kenya.

Although the idea of adding micronutrients to fertilizer seems simple, a lot of questions remain to be solved regarding sustainability, for example, the Zn stocks available will last only for about 20 years. Introduction of techniques at farm level is equally problematic: can we convince farmers to grow more healthy crops without yield increase and will consumers buy more expensive produce if the quality increase is not directly visible? Whatever the outcome, it is clear that with a growing population the problem of micronutrients must be solved. In our project we are testing the application of rock dust as soil conditioner, many rock dusts are known to be rich in micro nutrients and they can be valuable as a cheap source of plant-available iron3.

Footnotes

  1. 1. Traoré, M., Thompson, B., & Thomas, G. (2012). Sustainable nutrition security. Rome.
  2. 2. Black, R. E., Morris, S. S., & Bryce, J. (2003). Child survival: Where and why are 10 million children dying every year? The Lancet, 361, 2226–2234.
  3. 3. Barak P., Chen Y. & Singer A.  (1983). Ground basalt and tuff as iron fertilizers for calcareous soils. Plant and Soil 73, 155-158.
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