Keywords: Micronutrients, fertiliser coating, plant uptake

Past practices in using soil—applied micronutrients have entailed using sources of micronutrients that are formulated as large granules that are blended with macronutrient fertiliser. The problems with this technique are twofold: Firstly, granular micronutrient formulations have both a greater bulk density and different particle size distribution than typical nitrogen (N), phosphorus (P), potassium (K) dry blends – and thus segregate within blends during handling. Secondly, even when used at rates that are many times higher than crop requirements (for example 1 to 10 kg ha^-1), the dispersal patterns of granular micronutrients can result in inconsistent crop uptake, owing to the great distances from granule to granule within the soil.

Work was conducted by Wolf Trax Inc. to determine whether these two issues could be addressed. A hypothesis was proposed wherein a robust micronutrient formulation that was effectively coated onto the surface of various macronutrients could provide for more consistency in providing plant available forms of zinc, copper, boron, iron and manganese than that seen with traditional granular applications. The drivers of this improvement were postulated as being:

(a) improvement in evenness of fertiliser blend (and thus better distribution across a field), and

(b) more precise spatial placement of soil-applied micronutrients through the root zone coupled with incremental improvements in uptake owing to formulation techniques.

The net result from the work indicates that using the proprietary coating technique allowed for more even distribution of micronutrients through the root zone, with DTPA extractable levels of micronutrients (or hot water boron levels in the case of those tests) present across a variety of soils, and consistent uptake by a variety of crops, with efficacy as good as or better than granular nutrients applied at much higher rates. Examples of a small subset of these data are presented.

Mark Goodwin, Wolf Trax Inc., 800 One Research Road, Winnipeg, Manitoba R3T 6E3, Canada.

12 pages, 3 figures, 5 tables, 1 refrerence.