Nitrogen Fertilizer Application in Grass–Clover Elevated Nitrate Leaching in the Follow‐on Maize Crop

ABSTRACT

Background : Grass–clover and silage maize are key for dairy feed production and frequently occur within the same crop rotations. Fertilizer management in grass–clover may leave residual effects that influence both environmental outcomes and the performance of subsequent maize crops.

Aims : The study aimed to quantify how increasing cattle slurry nitrogen (N) application rates in grass–clover affect (1) nitrate leaching during the following maize phase and (2) maize growth and N status. The central research question was whether higher slurry N inputs in grass–clover elevate leaching losses and improve the productivity of subsequent maize.

Methods : A long‐term crop rotation experiment was used to assess legacy effects of graded slurry N fertilization in grass–clover. Nitrate leaching, maize dry matter yield, and plant N content were measured, along with N uptake by an intermediate cover crop.

Results : Higher slurry N rates in grass–clover significantly increased nitrate leaching during the maize phase, with 0.16–0.18 kg NO ₃ ‐N leached per additional kg N previously applied. In contrast, maize dry matter yield showed little response to slurry N history. Although maize N content varied among treatments, overall concentrations remained above critical thresholds for N limitation. Cover crop N uptake (0.4–9.6 kg N ha ⁻¹ ) was too low to account for observed leaching patterns, emphasizing the predominant influence of crop sequence and soil mineralization.

Conclusions : Slurry N fertilization in grass–clover can elevate nitrate leaching risks without reliably enhancing maize yield, highlighting the need for integrated N management to balance productivity and environmental protection.