SUBSURFACE ENVIRONMENTAL-QUALITY UNDER A CATTLE FEEDLOT AND ADJACENT CROPFIELD

The dynamic systems under consideration is complex. The behaviour and fate of chemicals in a feedlot environment and cropfield are affected by interactive variables such as environmental factors, management pra ctice, landscape, nitrogeneous waste types, site physical/chemical/ bi ological properties. The purpose of this study was to ascertain the su bsurface environmental quality under a cattle feedlot and manured adja cent cropfield, Soil cores from differently managed pens and a cropfie ld were parametized for key chemical and physical properties. The crop field has been manured for 20 years and fertilized with N at recommend ed rate of 120 kg ha(-1). The average amount of autoclave labile-N in the top 25-cm varied with soil cores and ranged from 30 to 67 mg kg(-1 ) and decreased significantly beyond the 0.50-m depth in all soil prof iles. Average total NO3-N loading in the vadose associated with pen-A, pen-B, pen-C and the cropfield was 58, 123, 212, and 234 mg kg(-1), r espectively. Average NO3-N concentrations in cores from pen-A, pen-B, pen-C and the wheat cropfield ranged from 1 to 39.5, 1 to 57, 1 to 81 and 6.8 to 54 mg kg(-1), respectively. No accumulation and penetration of NH4-N were found in any of the soil cores. Electrical conductivity values of the soil cores generally decreased as a function of depth w ith some upward spikes which likely indicate that previous leaching ha d occured in these profiles. On the other hand, a defined progression of decreasing Cl- concentration was found in all soil core profiles. H ighest concentrations of Cl- were observed beneath pen-B and pen-C whi ch were active. Ratios of Cl-/NO3-N computed for the pens and the crop field at all sampled depth and the E. C. values suggest that denitrifi cation occured in the soil profiles. Particle size analysis of the soi l cores indicated a medium to coarse-textured profiles at these sites. In light of these findings, significant potential for denitrification and nutrients movement in the soil profiles exists.