Vitrified has been kiln fired as a means of trying to cut down on dust. I don't know much about it other than a lot of nurseries and garden centers around here use it for their soil mixes when needed. Pelletized, as opposed to granular, generally breaks down the fastest as they actually grind pulverized lime again before gluing it back into the pellets. Pulverized lime is generally a pain to handle and spread since it blows around so easily. We switched over to pelletized about 10 years ago and even at 2-3 bucks extra per 50 lb. bag we've never had anyone complain that we didn't have pulverized.

Outside of a soil test it's just a guessing game, but if you need to fertilize every 3-4 weeks because the grass won't hold it's color chances are your soil is on the acidic side and the little grass plants just aren't able to utilize all of those nutrients before they leach through the soil.

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1980 300TD-China Blue/Blue MBTex-2nd Owner, 107K (Alt Blau) OBK #15
'06 Chevy Tahoe Z71 (for the wife & 4 kids, current mule) '03 Honda Odyssey (son #1's ride, reluctantly) '99 GMC Suburban (255K+ miles, semi-retired mule) 21' SeaRay Seville (summer escape pod)