No-tillage (NT) is becoming increasingly attractive to farmers because it clearly reduces soil erosion and production costs relative to conventional tillage (CT). However, the impacts of no-tillage on the quantity and quality of tile drainage water are less well known. Accordingly, two adjacent field scale on-farm CT and NT sites were established to compare the impacts of the two tillage systems on tile drainage and NO3-N loss in tile drainage water. The effect of the two tillage systems on soil structure, hydraulic conductivity, and earthworm population were also investigated. The total NO3-N loss in tile drainage water over the 5-yr period (1995-1999) was 82.3 kg N ha−1 for the long-term NT site and 63.7 kg N ha−1 for the long-term CT site. The long-term NT site had 48% more tile drainage (6,975 kL ha−1) than the long-term CT site (4,716 kL ha−1). The average flow weighted mean (FWM) NO3-N concentration in tile drainage water over the 5-yr period was 11.8 mg N L−1 for the NT site and 13.5 mg N L−1 for the CT site. For both tillage systems, approximately 80% of tile drainage and NO3-N loss in tile drainage water occurred during the November to April non-growing season. Long-term NT improved wet aggregate stability, increased near-surface hydraulic conductivity and increased both the number and mass of earthworms relative to long-term CT. The greater tile drainage and NO3-N loss under NT were attributed to an increase in continuous soil macropores, as implied by greater hydraulic conductivity and greater numbers of earthworms.
Soil phosphorus availability and soybean response to phosphorus starter fertilizer