Liquid forms of micronutrients can be applied to the soil as well as the plants themselves. In the latter case, the plant leaves absorb most of the application, but what misses seeps into the soil for later uptake. One study showed a liquid soybean application of micronutrients resulted in a 50-percent absorption by the plant within 2-10 hours.
M.E.E.N. Green is one such product. It comes dry but is mixed with water for liquid application. It contains a combination of nitrogen, phosphorous and potassium plus a variety of micronutrients that enhance plant growth and improve their taste appeal to deer.
Other liquid micronutrient fertilizers are available to treat a variety of specific plant needs. Some are sold in chelated forms that resist binding with the soil, which can make them less available to the plant.
You can buy single-nutrient additives such as 4-7 percent liquid manganese, as well as blends such as a zinc-iron, manganese-magnesium combination designed for soybean application from PureGrade. Some of these liquid application fertilizers can be combined with herbicide to accomplish two goals at once. Check labels before mixing.
Go slow and seek advice if you’re uncertain of the specific needs or portions you should apply to your plants and soils and exactly which micronutrients or blends would benefit them the most. And remember, keeping the pH neutral and the soil aerated through deep tilling or planting radishes will help make the micronutrients you apply most readily available to the plants.