The first phase of the HarvestPlus Zinc Fertilizer Project has assessed the potential for crop response to Zn-containing fertilizer in a number of target countries where soils are unable to produce staple foods with adequate Zn. Foliar spray of Zn fertilizers is highly effective in increasing Zn concentrations of cereal grains. However, attention should be paid to the timing of Zn spray. Soil application of Zn-containing fertilizers is more important for improving crop yields.
Cakmak, I. HarvestPlus Zinc Fertilizer Project: HarvestZinc. Better Crops with Plant Food (2012) 96 (2) 17-19.