More fluid approach needed for plant nutrition

Terry-TomatoTargeting soluble nutrients by spraying onto the foliage gives a more efficient outcome. (Image source: Dr Terry Mabbett)Targeting soluble nutrients by spraying or fertigation (nutrients dissolved in irrigation water) onto the foliage gives a more efficient and effective outcome

Plant nutrition mind-set is still largely focussed at ground zero on the spread of solid fertiliser formulations over the soil. Crop plant root systems are still regarded as prime points for nutrient entry but more modern fluid thinking sees the most easily and effectively targeted plant parts as those above-ground.

This is the philosophy and policy of Omex Agrifluids a research and development based company supplying soluble plant nutrients for foliar feeding to all parts of the world. “Good basal soil nutrition is essential but foliar feeding can provide useful complementary crop nutrition” said Alan Lowes (regional director) and Peter Prentis (export director) at Omex Agrifluids.

Nutrients applied to the soil as solid fertiliser run the gauntlet of soil associated risks that revolve around inappropriate soil pH, other competitive/antagonistic nutrients and the lock-up potential for nutrients by specific soil fractions. Key aspects of the gauntlet run by soil applied nutrients and bypassed or overcome by foliar feeding include:

Tie-ups between nutrients like calcium, phosphates, iron and zinc.

Excessively acid or alkaline pH soils locking up nutrients or enhancing their availability to phytotoxic levels

Leaching, volatilization and conversion losses related to nitrogen

Competition between similar elements such as sodium-potassium, calcium-magnesium, etc.

Fixation by clay fractions, metal oxides and anions like bicarbonates and phosphates.

A classic case quoted by Omex Agrifluids surrounds zinc locked up in naturally high alkaline soils (pH 8-9) with farmers still encouraged to keep on adding zinc to the soil. Net result is soils becoming a ‘bottomless pit’ for this essential plant micronutrient with serious economic and environmental implications.

“In such soil situations farmers must use foliar sprays to put the plant’s zinc requirement directly on the leaves. Zinc will enter the leaves unimpeded and to be rapidly used ‘on the spot’ and in its largest amount as a co-factor for enzyme actions and other metabolic functions that occur inside leaf cells,” said Alan Lowes.

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