Strategies to increase nitrogen use efficiency and reduce nitrate leaching in vegetable production in the Netherlands

Environmental concern and legislation of fertilization requires strategies to increase nitrogen use efficiency and reduce nitrate leaching. Strategies can be fertilizer choice, timing of N availability and fertilizer placement. Rainfall in the experimental year 2007 was moderate and different strategies were therefore not seriously tested. However, for crops that allow regular fertilization, it is questionable whether special fertilizers can do better than calcium ammonium nitrate (CAN) when fertilizers are applied according to good practice (i.e., row application, side dressing and split applications). Specific application of small amounts of N near planted endive showed increased initial growth, even at high levels of soil mineral N, and was found to lead in one of two plantings to increased yield at harvest. Substitution of broadcast N before planting by a starter application close to the plants followed by side dressing maintains maximum production while leaching risk is reduced