Early application of the readily available nutrients, especially nitrogen, stimulates rapid early growth that can be susceptible to diseases and insects, especially powdery mildew and aphids. Time-release fertilizers are inorganic fertilizers coated with a shell that allows water to pass in and out by osmosis. The rate of transfer is controlled by temperature, with only a small amount of diluted fertilizers passing out to the soil at 60 o , a greater amount at 70 o , and so on. In our area, where our soils do not heat up rapidly in the spring, time-release fertilizers generally are very slow to kick in until late June. Inorganic fertilizers come in granules or as water-soluble crystals.
Granular combinations are more flexible in containing a wider range of minerals.
Water-soluble fertilizers tend to be just nitrogen, phosphorous and potassium. Water-soluble fertilizers can be mixed at different strengths, and can be applied as a soil drench or as a foliar spray. The soil-drench is an effective way of getting fertilizer down to the roots, but will also flow right through. Add enough soluble fertilizer to make it half strength generally 15 Tbsp. Let it sit for a few hours to a couple of days.