Nitrate Leaching Losses Under Repeated Cattle Feedlot Manure Applications in Southern Alberta

Abstract

AbstractAn experiment was conducted at Lethbridge, Alberta, to determine the long‐term effects of annual applications of cattle manure on nitrate (NO3)‐N accumulation and movement, and to assess the environmental impact of such a practice. Manure was applied annually at 0, 30, 60, and 90 Mg ha−1 (wet wt. basis) and 0, 60, 120, and 180 Mg ha−1 (zero, one, two, and three times the maximum recommended annual application rate, respectively), to nonirrigated and irrigated Dark Brown Chernozemic (Typic Haploboroll) clay loam soils from 1973 to 1992. All plots were planted to barley (Hordeum vulgare L. cv. Galt) in spring each year. In the fall, duplicate soil cores were taken to a depth of 1.5 m. Water content (gravimetric), chloride, ammonium‐ and NO3‐N concentration of soil and manure samples were determined to estimate leaching and deep percolation loss of water and solutes. Level of manure and moisture regime affected the extent of NO3‐N increases. Under nonirrigated conditions, manure applied at one to three times the recommended rate resulted in a significant accumulation of NO3‐N in the root zone. However, minimal leaching loss was observed below 1.5 m except for a year with unusually high precipitation. On irrigated soils, contamination of soil and groundwater from repeated applications at or greater than the recommended rate of 60 Mg ha−1 was significant and annual losses may reach 93 to 341 kg N ha−1. Therefore, long‐term annual application of manure at the maximum recommended level is not advised because of potential soil and water contamination problems.