A method of preparing liquid nonpolymeric controlled release nitrogen plant food composition by the condensation reaction of about one molecule ammonia, about two molecules of urea, and about three molecules of formaldehyde in base buffered aqueous solution at a minimum pH of 7 and a temperature of about 100 C. and concentrating by evaporation until nitrogen concentration is between 20 and 30 percent before formation of polymers containing more than 3 urea moieties occurs. The new nonpolymeric aqueous liquid controlled release nitrogen plant food composition prepared exhibits high storage stability, low phytotoxicity, high nitrogen availability to plants, and contains less than 6 percent unreacted urea nitrogen, less than 1 percent unreacted ammonia nitrogen, and contains large amounts of 5-methyleneuriedo-2-oxohexahydro-s-triazine.
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