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

Abstract

Ige, D. V., Abioye, O. S., Akinremi, O. O., Nyachoti, C. M. and Flaten, D. N. 2011. Phosphorus solubility in Manitoba soils treated with pig manure from phytase supplemented diets. Can. J. Soil Sci. 91: 947–955. 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−1and 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.