Zinc seed dressings can effectively supply zinc to a young crop. The amount of nutrient that can be applied in a seed dressing depends on the size of the seed. Small seeds can carry less of the coating media than large seeds. Seed dressings do not apply sufficient zinc to provide carryover benefit to future seasons.
Seed dressings may not provide sufficient amounts of zinc to correct a severe deficiency. Severe deficiencies may require in-crop foliar top ups during the growing period. A foliar spray of 250 to 350 grams of zinc (Zn)/ha applied to growing crops between GS21 to GS30 can address a zinc deficiency in that year. Foliar applications will not have any carryover benefit for the following crop.
Using zinc enriched fertilisers at seeding or a spray of zinc onto the soil prior to incorporation are good options for that crop and for several following years. Apply at a rate of about 1 kilogram of Zn/ha, up to 2kg Zn/ha for a severe deficiency. Soil applications provide residual benefits in subsequent years, so can be more cost effective in the long run.
Planting seed retained from zinc sufficient paddocks is another way to reduce the risk of zinc deficiency occurring in young crops.
|Zinc deficiency in crops
Most vulnerable soil types: mallee soils (although all soils can be affected).
Most vulnerable crops: medics, durum and pulses.
Visible signs: one to two stripes mid-way up the plant in cereals. No symptoms in pulses.Diagnosis: tissue test youngest emerged leaves at GS30, standard soil testing is not conclusive.
This article was prepared in response to discussions between growers, advisors and researchers at the More Profit from Crop Nutrition Roadshows 2016.