Heavy metals and their influence on crops (part 3)
Heavy metals affect plant growth and can occur in the soil/soil, in groundwater and well water. Or come along through fertilizers or released from the cultivation system. In our accredited analysis for heavy metals in ground drinking and surface water, 13 metals are reported at a very sensitive management level in micrograms per litre. But we also measure heavy metals in crops or soil. Meanwhile, many growers notice that heavy metals are part of water quality. Some heavy metals accumulate through recirculation, which hinder the absorption of essential trace elements. In part 1 we discussed aluminum and arsenic, in part 2 we discussed barium, cadmium and chromium. Here we discuss cobalt, tin and nickel.
We measure aluminium, arsenic, barium, cadmium, chromium, cobalt, mercury, lead, nickel, tin and silver in the heavy metals package. Chromium-6, selenium, fluorine and iodide are special metals that we can do as additional analysis. We take measurements in water, fertilizers, (potting) soil/compost, seeds and crops and in fruit and vegetables. There are even MRLs for arsenic, cadmium, copper, mercury, lead.
Chromium-6, selenium, fluorine and iodide are special metals that we can use as additional analysis.
Cobalt occurs naturally in clay-containing soils and rocks (basalt). In greenhouse cultivation, cobalt mainly comes with raw materials that we add. Or when material (metal, paint, rubber) weathers, cobalt can end up in water. Cobalt also occurs in fossil fuel exhaust, so the level is increased along highways. Cobalt can be absorbed by plants via leaves and roots and can even promote growth at normal values. Although it is a non-essential element. If the values are too high, it results in leaf fall, discoloration of veins, folding of leaves and reduced crack growth. Cobalt is almost never found in horticulture in toxic levels. In the presence of cobalt in the root zone, it competes with iron and other metals and through this route presents a risk of iron deficiency. In agriculture, cobalt salts are given as fertilizer in grass for animal feed.
Tin is found in most soils. Most soils have been reported to contain about 1 to 4 mg/kg of tin. Much higher values are found in peat soil, 50-300 mg/kg is described. One speaks of contaminated soil from 900 mg/kg (d.s.). In Dutch groundwater about 2 µg/l of tin occurs, in seriously polluted groundwater up to 50 µg/l. In
About tin excess is only something described when waste water from a tin mine ended up at plants. Tin was virtually not absorbed by the plant, so that excess will not quickly be visible in the plant, at most it hinders the absorption of other metals.
In the soil, nickel occurs mainly in clay and iron-rich soils. Nickel can be absorbed by plants but can hinder the absorption of iron at the roots. Some crops can withstand higher levels and absorb a lot of them. Nickel is often found in higher levels specifically in seeds and fruit dishes. With too much nickel, roots develop poorly and iron deficiency occurs. Nickel, like copper and zinc, is widely used in building materials. Processing metal by galvanizing, chrome plating or nickel plating protects the metal. When weathering, these metals can enter the drainage water. Also, the fertilizer iron and rock flour (agriculture) often bring nickel. At low pH, acidification of the soil, nickel comes into solution and thus increased values of in groundwater occur. In groundwater the target value is less than 15 µg/l.
Aluminum and arsenic were mentioned in the Nieuwsmail Horticulture 2021-Q3. You can request that part again via this Contact button. And in the Nieuwsmail Tuinbouw 2021-Q4 a second part was offered with barium, cadmium and chromium. You can request that part again via this Contact button.
For more information, please contact Ines van Marrewijk.