Effect of dietary phytase supplementation on greenhouse gas emissions from soil after swine manure application

Abstract

Effects of supplementing swine diets with phytase on manure composition and greenhouse gas (GHG) emissions from soil after manure application were investigated. The experiment was laid out in a completely randomised 3 × 2 × 2 factorial design, with three manure treatments (no manure, manure from unsupplemented diet and manure from phytase supplemented), two soils (Carman and Gunton sandy loam soils from Southern Manitoba, Canada) and two moisture levels (low and high moisture with 0.50 and 0.80 water-filled pore space, respectively). Gas emissions were greater (P < 0.05) from high than from low moisture soils. Manure addition increased CO and NO emissions. When applied to high moisture soils, CO emission was increased and that of NO decreased when phytase manure was applied compared with non-phytase manure. Methane emission was not affected by manure addition or by type of manure applied. Inorganic N remaining in soil at the end of the experiment was greater with phytase than with non-phytase manure application. Plant extractable P concentrations in soil were reduced with phytase manure, probably due to lower total P added with the manure. For a successful dietary strategy to reduce GHG from manure, a good understanding of the soil properties that influence emissions becomes necessary. Supplementation of swine diets with phytase contributes to reduce disposal of P and N in manure, but has a limited effect on GHG emissions from manure amended soils. Emission of NO may be reduced using manure from piglets fed phytase supplemented diets to fertilise high moisture soils.