Simulation-based assessment of residue management to mitigate N loss risk in winter wheat production

Abstract

AbstractUnderstanding the interactions between nitrogen mineralization in soil and site-specific environmental factors is essential for developing tailored nitrogen management approaches in intensive agricultural systems. This study assesses the potential of residue management strategies to mitigate nitrogen leaching losses, focusing specifically on winter wheat following winter oilseed rape as a commonly practiced crop sequence in Germany with a high risk of N losses during the percolation period (August–March). Special attention has been given to the interactions of the proposed measures with extreme weather conditions that may become more frequent due to climate change. A well-established plant-soil process model implemented in the HUME modeling environment was used to evaluate the effects of incorporating, removing, or replacing oilseed rape residues with winter wheat straw at 10 sites over 25 years. Results highlight that precipitation exerts a greater influence on nitrogen leaching than local soil properties across the selected study sites. Winter wheat straw incorporation reduced total net nitrogen mineralization during fall by an average of 12 kg N ha−1 compared to the common practice of keeping the preceding crop residues. Surprisingly, the treatment effects on nitrogen leaching losses fall short of the expectation of a site-specific significant reduction. Most of the initial excess nitrogen remains in the upper layers of the soil profile accessible to wheat roots during the growth period, even in years of exceptional percolation. Nitrogen limitation due to persistent immobilization after winter wheat straw incorporation could not be effectively compensated, resulting in negative yield effects of about 11 ± 5 kg N ha−1. However, this treatment reduced the nitrogen surplus after spring droughts on average by 9.6 ± 4 kg N ha−1. Also, considering a farmer’s perspective, where the potential improvement in nitrogen efficiency must outweigh the additional costs of labor and machinery required to remove or replace residues, the results indicate that retaining the preceding crop residues is currently the most effective approach to mitigate nitrogen losses. Additionally, the study underscores the significance of accounting for site-specific and management-induced mineralization when estimating fertilizer demand to optimize agronomic productivity while minimizing the risk of nutrient losses through leaching.