Cotton requires most of its Zinc during flowering

By: David McRae

High yielding cotton production requires adequate zinc nutrition to efficiently convert radiant energy (heat & light) into complex sugars (cellulose). Zinc plays a key role in a wide range of enzymes and proteins, controlling many important biochemical pathways. These are mainly concerned with;

• Carbohydrate metabolism, both in photosynthesis and in the conversion of sugars to starch.
• Protein metabolism.
• Auxin (growth regulator) metabolism.
• Pollen formation.
• Maintenance of the integrity of biological membranes.
• Resistance to infection by certain pathogens.

The 2 most important growth stages for adequate zinc availability are;

• When the plant is small and has a poorly developed, sparse root system. Zinc is immobile and roots need to intercept available zinc for plant uptake.
• During flowering - early boll filling, when nearly 70% of the total zinc required is taken up by the plant (See Table 1)

Cotton requires most of its Zinc during flowering
Foliar application of zinc provides a readily available source of nutrient that supplies plant’s requirements for growth. Additional foliar phosphorus can be beneficial when soil uptake is restricted. Zinc and phosphorus absorbed by leaves is utilised rapidly, boosting shoot and root growth and supporting important biochemical pathways in the plant such as carbohydrate metabolism and auxin production.
The type of field activity and its timing creates opportunities for applying zinc and phosphorus foliars.

Listed below are 3 Yara foliar fertilisers which can either be applied broad-acre or in banded applications.

YaraVita GLYTREL ZnP contains complexed zinc and phosphorus and can be applied with Glyphosate to Roundup Ready cotton with no reduction in weed control. YaraVita GLYTREL ZnP is easy to handle, safe on the crop and is a fully formulated product containing wetters and stickers to enhance leaf uptake of zinc. 
YaraVita ZINTRAC is a highly loaded, fully formulated suspension concentrate, which allows low application rates, reduces handling and is designed for safe foliar applications. It contains its own wetters and stickers to ensure optimum zinc uptake through the leaf. 
Yara Liquids P-FOL Zinc is a zinc phosphate fertiliser that can be applied as a band or broadcast to correct zinc and or phosphorus deficiency. 
For further information on the importance of zinc in cotton production and Yara crop nutrition solutions for adequately supplying crop demands, click here.

Table 1

Table 1

Weekly nutrient uptake by weeks after planting.