Long-term nitrogen dynamics in various catch crop scenarios: Test and simulations with STICS model in a temperate climate

The long term effects of repeated catch crops on N dynamics in arable farming were assessed using mid-term experiments and long-term simulations. The soil-crop model STICS (v6.9) was tested against a database provided by three experiments (13–17 years) carried out in Northern France, including treatments with or without repeated catch crops. STICS performance was checked for crop biomass, N uptake, soil water content and mineral N at harvest of main crops, drained water, N leaching and mineralization rates. The model satisfactorily reproduced these variables, except for soil mineral N and N leached at one site. N leached was predicted with a slight bias, between −3 and +7 kg N ha−1 yr−1, and soil N mineralized was simulated with a bias lower than 7 kg N ha−1 yr−1. The model simulated correctly the N uptake by catch crops and the kinetics of extra N mineralization due to catch crops. Seven scenarios varying in the presence of catch crops, fertilization rate and climate were simulated on long-term (60 years); their effects on N uptake, soil N storage, N mineralization and nitrate leaching were compared by difference with a control scenario. Repeated catch crops lead to reduce N leaching, sequester organic N and increase N mineralization. The model indicated that the sequestered N reached a maximum of 430–750 kg N ha−1 after 23–45 years depending on site. The extra-mineralization due to catch crops progressively increased up to 38–65 kg N ha−1 yr−1. A strategy of constant N fertilizer rate resulted in raising the N uptake of main crops and slowing down the abatement of nitrate leaching. Conversely, when N fertilization rates were reduced by 20–24 kg N ha−1 yr−1, crop production remained stable and catch crops reduced N leaching on the long term by 33–55%. Therefore catch crop is a promising technique for controlling the N cascade.