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One experiment lasting for two years was carried out at Pegoes (central Portugal) to estimate the impact of mature white lupine residue ( Lupinus albus L.) on yield of fodder oat ( Avena sativa L. cv. Sta. Eulalia) as the next crop in rotation, comparing with the continuous cultivation of cereal, under two tillage practices (conventional tillage and no-till) and fertilized with five mineral nitrogen (N) rates, with three replicates. Oat as a first crop in the rotation provided more N to the agro-ecosystem (63 kg N ha −1 ) than did lupine (30–59 kg N ha −1 ). This was at a cost of 100 kg of mineral N ha −1 , whereas lupine was grown without addition of N. A positive response of oat as a second crop was obtained per kg of lupine-N added to the system when compared with the continuous oat–oat. The cereal also responded positively to mineral N in the legume amended soil in contrast with the oat–oat sequence where no response was observed, partly due to the fast mineralization rate of lupine residue and a greater soil N immobilization in the continuous oat system. Each kg N ha −1 added to the soil through the application of 73 kg DM ha −1 mature lupine residue (above- and belowground material) increased by 72 kg DM ha −1 the oat biomass produced as the second crop in rotation when 150 kg mineral N ha −1 were split in the season, independent of tillage practice. Mature legume residue conserved in the no-tilled soil depressed the yield of succeeding cereal but less than the continuous oat–oat for both tillage practices, where the application of mineral N did not improve the crop response. |
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