Is it too dry to apply bag nitrogen?

If it hasn’t rained in two weeks and the forecast is for no rain in the next two weeks, then halve or eliminate the inorganic nitrogen fertiliser application you are about to make. Don’t bother playing catch-up by applying more later, the opportunity has gone. Just ensure you make applications when the rain returns.

Although grass doesn’t need much water to take up nitrogen, morning and evening dew is not enough on a soil that has been dry for a couple of weeks. The dew will make fertiliser prills or granules disappear from a dry soil. However, the way that grass roots use nitrogen in the form of nitrate dissolved in water means transpiration must happen.

Transpiration is the movement of water from the soil, through the root, into the above ground growing point, stem, and leaves. This all needs soil moisture, not just a bit of dew.

When fertiliser is applied to dry soils, it risks losing nitrogen through volatilisation. This is the loss of ammonium-N from the soil as ammonia gas. Conditions that favour volatilisation most are warm and drying soils, particularly with a breeze.

 For more information see: Fertiliser use in dry conditions | AHDB