Integrating maize and triticale in grass/clover based dairy systems: examining yields and autumn soil nitrate levels

To establish N-efficient crop rotations with perennial ryegrass/white clover, maize and triticale, a 9-year field experiment was executed on an organic experimental farm in the Netherlands. Crop rotations with different levels of slurry (dairy effluent from the free-stall barn, average dry matter content of 7%) application were tested for dry matter (DM) yield, N yield, soil mineral N in autumn, soil organic matter and soil organic N. Maize cropping and slurry application both increased annual DM yield. However, the second year of grass/ clover following maize, maize itself and slurry applications each resulted in higher soil mineral N in autumn, increasing the risk of nitrate leaching losses. A rotation of 4 years of grass/clover, 2 years of maize and 1 year of triticale resulted in relatively high average annual DM production (12 t DM/ha/year) for Dutch conditions, with a higher potential N leaching loss in 2 out of 7 years.