Bioavailable N and P Supply From Liquid Hog Manure In the Northern Great Plains.

Manure is an important source of nutrients for crop production, however, repeated application combined with over application can result in a surplus of soil nutrients. Surplus nutrients are subsequently lost to the environment via surface runoff, leaching or soil erosion. Three studies in the Canadian prairies investigated soil nutrient dynamics and environmental impacts following liquid hog manure (LHM) application. Stumborg and Schoenau (2008) studied long-term manure application sites receiving 37, 74 or 148 kL ha^-1 yr^-1 spring-applied LHM.  Soil samples (0-15 cm) were collected in the fall of each year and labile phosphorus (P) was determined by Modified Kelowna (MK), Plant Root Simulator (PRS^TM) probes, water extractable and Olsen P fractions. At the first site the highest LHM application rate resulted in surplus P, whereas, at the second site all application rates resulted in surplus. Labile P determination methods were highly correlated with each other. PRS^TM probes were advantageous as this method is not based on soil type. Carley (2007) studied different LHM treatments (0, 37 and 37 +Super N (NBPT + DCD) kL ha^-1) to determine the benefits of applying a nitrification inhibitor. PRS^TM probes were employed to measure soil nitrogen (N) dynamics. Application of a nitrification inhibitor increased ammonium (NH₄⁺) supply early in the season depending on environmental conditions. Chen (2005) measured the effects of LHM rates and application method on nutrients in surface water runoff from five different watersheds. Soil nutrient supplies were measured before and after manure application. PRS^TM soil NH₄⁺ supply was a valuable predictor of runoff NH₄⁺ concentrations following LHM application. These studies highlight the importance of understanding nutrient release dynamics resulting from manure amendments in order to minimize environmental impacts.