Early Nutrient Use

Published 1 March 13

Early season nutrient use

  • Temperatures above 5°C means ryegrass will grow
  • It is vital there are sufficient nutrients in soil to drive this early growth.
  • In early spring level of nitrates in soil tend to be very low.
  • Nitrates are soluble and tend to leach away of the winter and very little is being released from soil organic material because bacterial activity is slow at low temperatures.
  • Grass growth response to nitrogen applications will not be massive in early season due to short day length and low temperatures but  a response of 10kgDM for every kgN applied and daily growth rates of 10-15kgDM/ha is certainly possible through February.
  • It's important to minimise losses.
  • If nitrates aren't taken up quickly by the grass plant then they are likely to be leached way.
  • Small applications of around 25kgN/ha (20units/acre) are the best approach to minimise the risks of leaching.
  • If soils become waterlogged at any point after application there is also a great risk of losing nitrogen as nitrous oxide.
  • Research conducted at IGER North Wyke showed very large losses using urea fertiliser as opposed to ammonium nitrate, particularly at high rates.
  • However at low application rates, and with applications made in damp conditions, urea can be a very cost effective fertiliser.
  • Soil phosphates are essential for early season root growth and as they are relatively insoluble they are available to the growing plant - but if indexes are below 2 then the grass plant will struggle to access enough to produce new roots.
  • Response to nitrogen will be far less if phosphate indexes are low.

 

Check list for early season nutrient applications

  • Buy a soil thermometer and check soil temperatures before applying nitrogen.
  • Small applications reduce the risks of losses.
  • Urea can be a cost effective way to apply early season N - if used in the right conditions.
  • Make sure P levels are satisfactory.
  • Target your most productive fields for early nutrient application; south facing, lighter soils, young leys.