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. (C) 2011 Elsevier B.V. All rights reserved.