Phosphorus Fertilization From Manure Biochars

When processed via pyrolysis, livestock manures have the potential of providing energy and biochar.  The biochars are high in nutrient content, especially potassium and phosphorus.  Thus, they must be applied in accordance with their nutrient supplying capacity.  This capacity will be affected by factors such as manure type and processing conditions.  In this greenhouse study, investigations involved five manure sources: swine; dairy; beef; feedlot; turkey; and poultry litter.  The biochars were produced at temperatures of 350°C or 700°C.  They were applied to a Norfolk sand that was low in phosphorus content at a rate of 50 mg of P per kg soil.  The P was supplemented with 50 mg of N per kg of soil.  The soil was placed in small pots and seeded with ryegrass.  The ryegrass was grown for approximately seven weeks.  All of the biochars supported dry matter production equivalent to chemically applied phosphorus and potassium.  The temperature effect varied somewhat with manure type.  However, the most important conclusion was that the phosphorus and potassium of the biochar were readily available to the ryegrass.  Initial results of a subsequent experiment indicate similarly results for cotton.