Nutrient Release from Cover Crops
Cover crops can capture, fix and return meaningful nutrients, but consistently converting capture into timely nutrient use and having confidence to adjust fertiliser plans requires a more strategic mindset than simply putting seed in the ground, and an evidence base suitable for UK climate and soils.
In UK conditions, well‑grown winter covers typically supply around 20-30kg N/ha, with higher amounts possible where management and conditions align. We are determined to move this conversation beyond rules of thumb by working with farmers to generate practical, field‑scale data on nutrient release dynamics, enabling everyone to estimate fertiliser adjustments with greater certainty.
Rigorous science, real‑world testing and shared learning, across countries as well as among ourselves, is our direction of travel.
What the UK evidence shows (at a glance)
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Strategic species selection and well‑timed destruction help increase quality of cover (including carbon to nitrogen (C:N) ratio and % of N), and therefore help ensure that nutrients mineralise when the following crop can use them, not weeks (or even months) too early or too late
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Trials in 2021-23 as part of the NiCC project showed earlier and greater mineral N availability to the following crop after chemical terminations versus mechanical methods (e.g. rolling on a frost or chopping and incorporating)
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If making any adjustments at all, growers typically treat a well-grown cover crop destroyed before the end of February as SNS +1 and reduce nitrogen by up to around 30kg/ha (AHDB), although RB209 guidance states that cover crops may increase SNS by up to two indices
