Phosphorus solubility in Manitoba soils treated with pig manure from phytase supplemented diets.

摘要

Phytase supplementation has been shown to reduce manure P content. However, this manipulation can influence manure P solubility upon land application. Therefore, the objectives of this study were to investigate the solubility of P in soils amended with manure from diets with reduced or no inorganic P supplement with and without phytase addition and to evaluate the influence of soil type on the solubility of manure P from phytase supplemented pig diets. Two calcareous and two non-calcareous Manitoba soils were amended with manure produced by pigs that were fed with diets containing different levels of supplemental inorganic P with and without phytase. Manure was applied at the rate of 75 kg P ha-1 and the amended soils were incubated for 1, 4 and 16 wk. Soil P was extracted with water (H₂O-P), Olsen (Ols-P) and Mehlich-3 (M3-P) solutions. Manure application mostly increased H₂O-P above the control. Complete removal of supplemental inorganic P from the diet irrespective of phytase addition significantly increased M3-P (P<0.05) in the two calcareous soils during the 16-week incubation. Similarly, when no supplemental inorganic P was included in the diet, Ols-P was increased in the fine textured, calcareous soil at 16th week of incubation. Thus, the complete removal of inorganic P from pig diet has potential to increase P solubility in some soils. Addition of phytase to pig diet did not have consistent effects on the soil extractable P in these soils. Soil factor had the greatest influence (77 to 94%) on P solubility. Our results showed that while phytase supplementation with concurrent reduction in inorganic P will reduce manure P with no adverse effect on P solubility in soils, total elimination of dietary inorganic P through the use of greater rate of phytase may not be feasible as this has the potential to increase P solubility in some soils.