Potassium leaching following silage maize on a productive sandy soil

Relatively little is known about potassium leaching losses following harvest of silage maize. While direct negative impacts on the environment are unlikely, losses of K with leaching need to be known for accurate balancing, especially on coarse textured soils, where K can be a critical element. In a four-year field experiment the effects of fertilizer forms (inorganic, cattle slurry and pig slurry) and four levels of N input (0, 80, 160, 240 kg N/ha) with corresponding amounts of K on the nutrient balances and leaching of K from silage maize grown on a sandy soil were investigated using suction cups. After four years, surplus of K from cattle slurry led to higher lactate-soluble K in the topsoil. Potassium leaching differed between years with different amounts of rainfall during winter. Annual leaching losses of K increased with N and K input and amounted to 38 kg K/ha, while fertilizer form had no significant effect. Losses of K increased with increasing N leaching (R2 = 0.69). We conclude that in maize production on coarse textured soils and under conditions of high N leaching (86-152 kg N/ha), K leaching can be large (6-84 kg K/ha) and constitutes a relevant part of K balances (-84 to +127 kg K/ha).