Nitrogen mineralization, plant uptake and nitrate leaching following the incorporation of (15N)-labeled cauliflower crop residues (Brassica oleracea) into the soil: a 3-year lysimeter study

A 3-year field lysimeter experiment was performed to determine transformations of 15N-labeled cauliflower (Brassica oleracea) residues incorporated into lysimeter topsoil in a potato (Solanum tuberosum)/cauliflower rotation. Only the potato crop received 150 kg mineral N ha(-1)y(-1). Cauliflower yields were high (12-13 t fresh matter ha(-1)), and N returned to the soil represented 51% of the aboveground plant N uptake. The 15N recovery by the potato/cauliflower rotation began at 46%, then decreased sharply to 12 and 6% for the second and third year, respectively. The cumulative 15N leaching rate was only 3%; 63% remained in the soil 3 years after incorporation. Soil N mineralization rates described by a parallel first-order kinetic model predicted 27, 7 and 6% of residual N lost annually during the first, second and third year, respectively. Thus, a potato/cauliflower rotation with moderate N fertilization optimizes N recovery of crop residues and can control leaching loss efficiently.