Soil nitrogen dynamics in different maize cropping systems

For a better understanding of soil nitrogen dynamics in maize cropping systems, Nmin content of soil and soil water samples from 0 to 100 cm depth were measured periodically in a loamy Cambisol near Zurich, Switzerland, from 1998 to 2000. Maize was sown either with conventional tillage (CT), rotary band seeding (RBS), or no-tillage (NT) after a previous crop of ryegrass and red clover. NT was also used after different annual green manure crops. Weeds were controlled with herbicides and a total amount of 145 kg N/ha was applied in three split applications to the maize plant rows. Between sowing of the maize crop and the 6-leaf stage of the plantlets, nitrogen dynamics were mostly influenced by the weather conditions and the intensity of soil tillage: In 2000, when the weather was warm, the maximum Nmin content in the soil after an application of 90 kg N/ha was 250 kg N/ha in all tillage systems. However, in 1999, when the weather was cool and humid, Nmin content in the soil was 50 % lower than in 2000. The ranking of the calculated N leaching losses was NT before RBS and CT, probably due to a delayed nitrogen mineralization and a higher water content in the soil after NT in contrast to RBS and CT. When N-fertilization was adapted to plant needs, most of the available mineral nitrogen in the soil was taken up by the maize plants during the 8-week period of fastest growth from the 6-leaf stage to milky ripe stage and the Nmin content in the soil after harvest of the maize crop at the end of September did not exceed 20 kg N/ha. In conclusion, NT and to a lesser degree also RBS are recommended as cropping systems for the improvement of soil structure and for the prevention of nitrate leaching.