It depends on the nutrient in question. Nearly all (research shows 70 to 90%) of the phosphorus (P) and potassium (K) are available in year 1 of a manure or compost application. Nitrogen (N) from fresh manure has about a 50 to 60% first-year availability with the remaining N becoming available in years 2 and 3. However, N availability from composted manure is about 25% in year 1 with the remainder becoming available over another four years. If compost is the main source of manure nutrients for a cropping system, it is best viewed as a P and K source rather than a N source because of the slow N availability.

Author: Ron Wiederholt, Nutrient Management Specialist, North Dakota State University