Abstract
Ley phases in crop rotations can supply nutrients to subsequent crops through organic matter mineralisation. However, the persistence of these effects and the relative contributions of mineral and organic fertilisation remain poorly understood. Based on an irrigated rotation with a four-year ley followed by four years of maize, a field experiment was established in the first maize year after the ley. The trial followed a completely randomised design with seven treatments and three replicates: mineral nitrogen (N) at 50 (N50), 100 (N100), and 200 (N200) kg ha⁻¹; farmyard manure (FYM) at equivalent N rates (FYM50, FYM100, FYM200); and an unfertilised control (N0). Over two years, maize was grown as the main crop, followed by oat as a cover crop. In the first maize cycle, no significant treatment effects were observed, with dry matter yield (DMY) ranging from 19.4 to 26.0 t ha⁻¹. In the second maize cycle, DMY under N200 and FYM200 was significantly higher than the control (26.0 and 23.9 vs. 17.4 t ha⁻¹). Compared with mineral fertilisation, FYM initially resulted in lower maize dry matter yield (DMY) but increased oat DMY and improved maize DMY in the second cropping cycle. Across the four-crop sequence, mineral and organic fertilisation resulted in comparable DMY and N recovery in aboveground biomass. The ley phase contributed significantly, but temporarily, to crop nutrition. Mineral and organic fertilisation gave similar productivity, but mineral fertilisers increased residual soil N in autumn, whereas organic amendments suggested a potential long-term advantage.