In general, organic fertilizers contain a lower percentage of nutrients than their inorganic counterparts. Some exceptions are 13% nitrogen in dried blood meal and 23% phosphorus in bone meal. Furthermore, manures are low in nitrogen, phosphorus and potassium (N-P-K). The analysis for chicken mature (dry) is nitrogen 2-4.5%, phosphorus 4.6-6% and potassium 1.2-2.4%.
Even at 4% nitrogen, 25 lbs. of manure are needed to supply one pound of nitrogen, whereas only 6 lbs. of 16-16-16 fertilizer would be needed to supply the same one pound of nitrogen.
Manures, however, offer a lot more than just N-P-K:
· They add organic matter to the soil.
· They help improve soil structure.
· In addition to N-P-K, they also add zinc, manganese, magnesium, calcium and sulfur.
· Manures improve water infiltration and the nutrient-holding capacity of soils.
· Manures can act as a food source for many beneficial microorganisms living in the soil.
In general, 3 – 10 tons of manure, per acre, can be applied. For smaller backyard gardens, applying 15 – 50 pounds of manure per 100 square feet of soil is suggested. Chicken manure contains salts which can burn plants; all manures of course contain some salts. Rainfall safely leaches these salts beyond the root zone of plants. In areas of low rainfall, caution must be exercised with repeated applications of large dosages of manure, especially chicken mature.
