Available nitrogen and phosphorus in soil amended with fresh or composted cattle manure containing straw or wood-chip bedding

Limited research exists on the effect of fresh versus composted beef cattle manure containing straw or wood chips on available N and P in the Great Plains region of North America. Barley was grown (1999-2007) on an irrigated clay loam soil in southern Alberta where organic amendments and fertilizer were applied annually for 9 yr from 1998 to 2006. The treatments were three rates (13, 39, 77 Mg dry wt. ha-1) of fresh manure (FM, stockpiled for up to 2 m) or composted manure (CM) containing either straw (ST) or wood chip (WD) bedding, one inorganic (IN) fertilizer treatment, and a unamended control. The soil was sampled in the fall of 1999 to 2002, 2004, 2006, and 2007 and was analyzed for soil inorganic N (SIN), NO3-N, NH-4N, and soil test P (STP). Soil mineralizable N was also determined on surface soil samples collected from 1999, 2002, 2004, and 2007. Manure type had a significant effect on SIN, NO3-N, STP, and soil mineralizable N, but the effects varied with year or bedding and rate (SIN), rate or year (NO3-N), rate and year (soil mineralizable N), or bedding and year (STP). Analysis of covariance for total N or P applied versus SIN or STP after nine applications (2007) indicated greater N release for FM and CM bedded with straw than with wood, whereas P release was similar for FM and CM with straw or wood. Soil NO 3-N for the organic amendments exceeded the maximum agronomic limit of 21 mg NO3-N kg-1 for Alberta after 6, 4, and 3 yr of application at the three increasing application rates. The STP for the organic amendments exceeded the maximum agronomic limit of 60 mg kg-1 for Alberta after 4, 2, and 2 yr of application at the three increasing rates. Overall, manure type and bedding material influenced the potential for nutrient losses to the environment through accumulation of soil inorganic N and soil test P; however, their effects on nutrient accumulation varied with year and application rate.