| This study aimed at improving the fertilizer value of manure by evaluating the N transformations of acidified (MA) and non-acidified (MNA) manure in soils and N uptake by corn; comparing them to an inorganic fertilizer, and at manipulating swine diets to obtain an optimally balanced manure to meet the crop nutritional requirements.; Manure acidification did not affect corn yields, N uptake, or 15N recovery. Total N uptake in plant biomass was highest for 250 kg N ha-1 ammonium sulfate (AS), followed by the manured treatments, 125 kg N ha-1 AS, and the control plots. AS 250 produced the highest NO3--N levels in soils during the reproductive stages of corn and consequently corn yields for this treatment averaged 13.1 Mg ha-1, followed by MA and MNA with an average of 12.5 Mg ha-1, and AS 125 with 12 Mg ha-1. The highest plant biomass N recovery at R6 was observed for the inorganic fertilizer treatments, averaging 47%; 15N recovery in the manured treatments was lowest (28%). The second year corn crop recovered 3.5% of amendment-15N, and an average of 31% of N added in MA, AS 125, and AS 250 and 8% added in MNA were found in the soil after corn harvest.; In a second study, six diets consisting of 2 P levels (0.5% and 0.3% + phytase), and 3 crude protein (CP) levels (9, 15, and 21%) were each fed to 30 gilts consecutively. Manures were soil injected at a P rate of 32 kg ha-1, and 6 inorganic fertilizer rates (0, 45, 90, 134, 179, and 224 kg (NH4)2SO4-N ha-1) were broadcast in the field in a RCB design with 4 reps.; Manures originating from pigs fed phytase supplemented diets and medium or high protein produced the highest corn yields (averaging 15 Mg ha -1), similar to those obtained with comparable inorganic N rates.; Soil extractable P levels (0--30 cm) after corn harvest were increased by 1.5 mg kg-1 Bray P1. Nitrate-N present in manured soils (0--90 cm) after harvest did not differ from soils receiving the same inorganic N rates, and averaged 17, 24 and 30 kg NO3--N for the low, medium, and high CP manures, respectively. |
