To asses the effect on crop yield of multiple rates and application strategies of micronutrient fertilizers in soils deficient in the target micronutrients (copper, zinc, manganese, boron and molybdenum)

From this trial:

• The site was severely deficient in Cu for wheat. 
• Under these severely deficient conditions, soil applications of Cu were poorly effective compared to foliar sprays but fluid applications performed better than Cu enriched granular fertilisers.  However, soil applications of Cu can persist for decades.
• There was no evidence that a chelated source of Cu as a foliar spray was more effective than a sulphate source and less Cu seemed to end up in the grain with the chelated source.
• A single foliar spray of Cu prior to flowering is often sufficient to protect a cereal crop from Cu deficiency but under the severe deficiency encountered in 2015, two foliar sprays were necessary to overcome the problem completely (one at first node, the second prior to flowering).
• Cu deficiency can make a crop more sensitive to adverse conditions.  In this trial, the hot drying conditions of the early October weekend, severely scorched all plots with no or poorly effective Cu management strategies.
• The soil and leaf tests taken during this trial support that the current guidelines for Cu deficiency are still relevant to modern farming systems and varieties.  A DTPA Cu level in soil of less than 0.3 ppm in the top 10 cm is considered deficient, and 1.3 ppm Cu in YEBS is considered very deficient for wheat.

From the whole project:

Current guidelines are still relevant and effective for TE management.

Some current interpretations of soil tests are causing issues - the suggested levels to avoid deficiencies are much higher in some lab reports than is our experience from field trials. These are creating false impressions of the extent and severity of Zn and Cu deficiencies.

No evidence of a major increase in the incidence or severity of TE deficiencies in the cropping zones.

Fluid delivery of TEs at seeding is a valid management strategy but rates of the target TE need to be the same as used with compounded fertilisers.

Generally, all sources of foliar TE were equally effective.