Excess Winter Rainfall

What is excess winter rainfall (EWR)?

Excess winter rainfall (EWR) is the amount of rainfall the land receives after the soil profile becomes fully wetted in the autumn (field capacity) and before the end of drainage in the spring (around the end of March). Ideally, the calculations should also take account of evapotranspiration during this period.

EWR has an important influence on the amount of nitrate leached and, thus, the nitrogen availability to a crop. It must be taken into account when planning nitrogen applications.

Latest EWR maps

• AHDB uses Met Office UK data* to present EWR data over 199 40km by 40 km squares
• Four maps are produced, one for bare soil, one for winter wheat, one for winter barley and one for winter oilseed rape (the latter crop has a larger canopy and records the lowest EWR)
• EWR deviation from the long-term average (1981 to 2010) is also provided
• The map is updated during the winter months