EFFECTS OF HOG MANURE ON NITROGEN AND PHO SPHORUS LOADS IN RUNOFF WATER FOLLOWING SIMULATED RAINFALL

Total Kjeldahl (TKN), ammonium (NH4-N) and nitrate nitrogen (NO3-N), t otal phosphorus (PT) and orthophosphate (PO4-P) loads were measured in the runoff following rainfall after hog manure was applied to a Coati cook clay loam soil (Humic Gleysol) in boxes of 0.26 m2 area with a 3% slope, containing 400 mm of soil. A factorial treatment combination o f three hog manure application rates (0, 27.3 and 54.6 m3.ha-1) with a nd without incorporation, two simulated rainfalls with s ring time int ensities common in Southeastern Quebec (11 mm.h-1 for 142 min and 22 m m.h-1 for 71 min for a total application of 26 mm) and three different rainfall delays (1, 24, and 48 h between time of manure application a nd beginning of each rainfall) were studied. Hog manure had little eff ect on TKN and NO3-N in runoff. More than 99% of TKN losses in runoff water were in the form of NH4-N. Runoff from soils having received hog manure at the highest application rate (54.6 m3.ha-1, 230 kg Of NH4-N .ha-1) was eleven times higher in NH4-N than that from untreated soil. Surface application of hog manure significantly increased all forms o f nitrogen and phosphorus losses, especially when rainfall was applied within the first hour after application. Incorporation into the soil had no significant effects on nitrogen and phosphorus loads. At the on e hour rainfall delay, surface application of hog manure produced a si gnificant quadratic effect on NH4-N loads (0.06, 6.8, and 40.6 kg.ha-1 ) which corresponded to the manure rates. For the two other rainfall d elays (24 h and 48 h) manure rates had a linear effect with much lower loads. Total phosphorus and orthophosphate loads were in form to thos e of ammonium nitrogen but with much lower values. To minimize all run off pollution by nitrogen and phosphorus, optimum amounts of hog manur e for plant requirements must be incorporated into the soil within 24 h before a rainfall event.