In this video Doc talks about lawn fertilizer numbers and particle size.
The new PGF Lawn Fertilizer will be available end of March 2019 on Amazon.
The new PGF granular fertilizer.
To select the appropriate particle size for a turf area, there are several factors to consider, the most important being height of cut (HOC). The smaller the particle size, the more particles that will be distributed per unit area and this will then affect the efficacy of the distribution of nutrients.
For example, a fertilizer with an SGN of 100 could have 15 times more particles in a given area than a SGN 300 product. When applying nutrient sources that will produce a color response such as nitrogen, iron and magnesium to an area with a lower height of cut (e.g. golf course greens, tees and fairways) it is necessary to use a fertilizer with a lower SGN to ensure a better distribution of nutrients.
Using a larger fertilizer granule than what the height of cut dictates could result in a speckled appearance, especially if the turf is “hungry” or the soil is cold. Additionally, if a slow-release fertilizer uses a coating as its control mechanism, matching the particle size to the height of cut is especially important to limit the number of particles damaged by reel mowers. If the coating is compromised, the nutrient will be released all at once, negating the effect of the slow-release mechanism.