Influence of water regime on nitrate losses in the watertable for maize, potato and sunflower crops.

摘要

The effect of different water regimes, on soil nitrogen dynamics and on nitrogen leaching in relation to nitrogen fertilization rate was examined in three crops. The trials were conducted from 1995 to 1997 using drainage lysimeters protected from rain in a shallow, coarse-textured and slightly-basic soil in Italy. The risk of high leaching losses corresponded with the beginning and the end of each crop-cycle (spring and autumn) when climatic conditions enhance organic matter mineralization and nitrification but N-uptake by crops is low. Nitrate leaching was related to high soil NO3-N as a result of fertilization: N leaching losses were higher when the highest rate of fertilizer was applied both in maize and potato. In sunflower even the intermediate rate (120 kg/ha N) resulted in remarkable N losses. When leaching occurred after a crop cycle (autumn and winter), NO3-N losses in drainage water were 54% of the annual total amount and were 12.7 kg/ha, following maize crop, 44.4 kg/ha, following potatoes and 30.0 kg/ha, following sunflower.