Potential of Poultry Litter Biochar As a Substitute for Inorganic Phosphorus Fertilizer.

Agriculture may contribute to eutrophication of water bodies through fertilizer application in excess of plant needs. Phosphorus (P) is an important nutrient for crop production, but when P is lost from the soil via surface or subsurface flow, it poses a threat to the environment. Poultry litter biochar (PLB) is an alternate source of P for crop production. The presence of a sparingly soluble phosphate mineral in the PLB could likely supply P to plants for longer periods with less P loss to the environment. Our objective was to evaluate the effects of PLB added at the same rate as inorganic fertilizer as a P source. The experiment included three treatments (inorganic P fertilizer, poultry litter biochar added at the same recommended total P as inorganic fertilizer, and a control with no P application) arranged in six replicates of a randomized complete block design at two locations differing in soil type (Entisols vs. Spodosols). At each location, the annual cropping system consisted of three phases, rye, corn for silage, and sorghum. Crop yield and N and P in plant tissue were measured for each cropping phase, and soil P storage capacity (SPSC, a measure of the amount of P a soil can hold prior to releasing P) was determined after each crop was harvested. There was no negative impact of PLB application on P and N in the plant tissue after the first two cropping cycles. Preliminary results also suggest that SPSC was similar at a given site with PLB or inorganic fertilizer applications. Evaluation of treatments over a longer time scale is expected to result in greater soil accumulation and less loss of P for PLB compared with inorganic fertilizer.