Nitrogen Availability From Natural Organic and Synthetic Fertilizers.

Nitrogen (N) availability from five natural organic (NO) fertilizers manufactured from a variety of nutrient sources was quantified by measuring N uptake by perennial ryegrass (Lolium perenne L.) over a two-year period. Nitrogen sources in the NO products included feather meal, soybean meal, blood meal, dried poultry manure, dried poultry waste, nitrate of soda, or dried biosolids. Three synthetic fertilizer sources [ammonium sulfate (AmS), calcium nitrate (CaNO3), and polymer coated sulfur coated urea (PCSCU)] were also included. Cumulative recovery of N in leaf tissue over two years was highest from CaNO3. Nitrogen recovery from PCSCU was 85% of that from CaNO3. Relative N recovery from the five natural organic sources averaged 73% (range 67% to 80%).  Although total recovery from the NO fertilizers was similar, seasonal recoveries (measured in April, June, September, and November) varied by as much as 250% between products during some seasons.