INFLUENCE OF INCUBATING MONOCALCIUM PHOSPHATE WITH LIQUID HOG MANURE ON INORGANIC PHOSPHORUS, ORGANIC PHOSPHORUS AND PHOSPHORUS AVAILABILITY IN 2 QUEBEC SOILS

The effects of incubating monocalcium phosphate monohydrate (MCPM) with liquid hog manure (LHM) on P availability and uptake by Italian ryegrass (Lolium multiflorum Lam.) were evaluated in a 99-d growth chamber experiment. Liquid hog manure with (0.738 g P kg-1 fresh LHM) or without MCPM was aerated for a 21-d period at 24-degrees-C. The soils used in this experiment were an Ormstown silty clay loam (Orthic Humic Podzol), and a Ste. Rosalie clay loam (Humic Podzol). Five treatments were applied to each soil: (i) control with no LHM or MCPM additions, (ii) MCPM, (iii) LHM incubated without MCPM, (iv) LHM incubated with MCPM, and (v) the separate applications of MCPM and LHM incubated without MCPM. Rates of MCPM and LHM applications were 513 kg P2O5 ha-1 and 32 t ha-1, respectively. Incubating LHM with MCPM resulted in a loss of 6% of the total manure-N during the 3-wk incubation period, compared with a 67% loss from the unamended LHM. Additions of both MCPM and LHM had the same effect on shoot-P contents and soil P fractions regardless of whether the materials had been incubated together or added to the soil separately. When compared with adding MCPM only, LHM-MCPM mixtures resulted in greater ryegrass shoot-P contents for plants growing on the Ste. Rosalie soil. However, this increase was approximately equal to the response to LHM additions, and thus presumably not due to improved MCPM P availability. Additions of both LHM and MCPM did not affect soil inorganic P forms compared with the lone addition of MCPM, but sodium hydroxide extractable organic P and sodium bicarbonate extractable organic P tended to be higher when just MCPM was added.