foliar fertilisersDo they work?

The word chelate derives from the Greek word “chel”, meaning a crab’s claw, and refers to the pincer-like manner in which the metal is bound. Chemically, a chelate is a compound from complexing of cations with organic compounds resulting in a ring structure.

The significance of chelation process in soil are:

1. Increase the availability of nutrients.

Chelating agents will bind the relatively insoluble iron in high pH soil and make it available to plants.

2. Prevent mineral nutrients from forming insoluble precipitates.

The chelating agents of the metal ions will protect the chelated ions from unfavourable chemical reactions and hence increase the availability of these ions to plants.

3. Reduce toxicity of some metal ions to plants.

Chelation in the soil may reduce the concentration of some metal ions to a non-toxic level. This process is usually accomplished by humic acid and high-molecular-weight components of organic matter.

4. Prevent nutrients from leaching.

Metal ions forming chelates are more stable than the free ions. Chelation process reduces the loss of nutrients through leaching.

5. Increase the mobility of plant nutrients.

Chelation increases the mobility of nutrients in soil. This increased mobility enhances the uptake of these nutrients by plants.

6. Suppress the growth of plant pathogens.

Some chelating agents may suppress the growth of plant pathogens by depriving iron and hence favour plant growth.

The significance of chelation process in soil are:

The organic coating around the chelated nutrient allows it to penetrate through the wax into the leaf. Once in the leaf, the chelate releases the nutrient so that it can be used by the plant.

Inorganic nutrient cannot easily penetrate waxy leaf

Chelated nutrient penetrates into leaf

Chelate releases nutrient

Feel free to contact us and ask about any of the products listed.

SMS Buffer
SMS Zinc (8%)
SMS Zinc + Boron
SMS Boron (B 8%)
SMS Molly (Mo 4%)
SMS Iron (6.25% Fe)
SMS Cal N + Zn + BO
SMS Cooper (Cu 5%)
SMS Nitrogen (N 32%)
SMS Polyphos (P 10%)
SMS Zinc (6%) + Mn (2%)
SMS Manganese (Mn 8%)
SMS Nitrogen (N 32%)
SMS Polyphos (P 10%)
SMS Zinc (6%) + Mn (2%)

Foliar sprays vs soil granular fertilisers

The following information is to used as a guide only. These estimations are based on scientific principles of soil and plant chemistry, and also to a great extent, on our experience over the past 10 years using these products in many crops in various growing conditions on many soil types. It is not our philosophy that granular fertilisers should be replaced solely by foliar sprays, but rather that the strategic and supplementary use of foliar sprays can be advantageous, efficient, practical and cost effective. This is in line with our philosophy of a ‘balanced nutrition approach’ produces healthy plants, and healthy plants produce good quantities of quality produce.

Some general rules of thumb:

  • A good chelated nutrient has a plant availability of 50-100%
  • A non-chelated nutrient has a plant availability of less than 10%
  • Foliar sprays provide little or no residual levels of nutrients in the soil
  • The efficiency of most soil applied granular fertilisers is less than 50 % (at least half is lost)

Foliar sprays vs soil granular fertilisers

With phosphorous the efficiency of foliar application is so much superior to granular forms that it is now an economic alternative to replace soil application completely with foliar sprays and seed dressings providing there is reasonable amounts of total phosphorous in the soil. This is because on most soils granular P availability is less than 10% for the period of the growing season. Therefore if I apply 100 kg/ha MAP or 22 kg/ha P on a clay soil, pH 5.5, the crop will receive about 2 kg during the growing season. If the soil is a calcareous clay with pH 7.5-8.5 the crop will only receive 1 kg or less of the 22 kg applied. In contrast, SMS POLYPHOS delivers an 85%+ plant availability. There are many reasons for low availability of granular phosphorous. On acid soils the main culprits are aluminium, iron and manganese ions that form strong and largely insoluble bonds with phosphates and this is most pronounced at pH 4.0-4.5 where P availability may be less than 5%. At best phosphate availability may reach 25% at pH 6.5, but this would only be on light sandy soils. Liming may also temporarily reduce P availability due to the formation of insoluble calcium phosphate, which is the main offender in alkaline soils with high limestone contents. The other factor on acid soils is incorporation of P into organic matter which can contain a significant proportion of the total soil phosphorous.

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