Getting to grips with residual nitrogen from cover crops

Nitrogen is directly linked to the protein content of malting barley. Getting that protein content right is the big challenge faced by farmers, as so many different factors affect nitrogen uptake by the plant.

Weather, fertiliser rate, application timing and soil nitrogen supply are just some of those factors. More and more farmers are now planting cover crops to take up nutrients, protect the soil over winter and improve soil structure on malting barley ground.

Knowing how those crops will affect your nitrogen supply is essential.

Eoin Lyons – adviser on the Teagasc/Boortmalt joint programme – told AgriLand about a trial set up on John Crowley’s farm in Co. Wexford this year to examine the soil nitrogen supply from cover crops.

A cover crop of mustard was planted on this monitor farm and the first thing to be investigated was establishment method.

There were four different establishment methods in the trial:
  • Direct drill;
  • Disc drill;
  • A disc and seeder;
  • Broadcast onto uncultivated stubble.

The different establishment methods will be carried into the experiment in the spring time and the following spring barley crop will be monitored for crop nitrogen uptake.

Different fertiliser nitrogen rates will be applied, while there will also be a plot which does not receive any fertiliser nitrogen.

A crop of mustard on John Crowley’s farm

This plot – which does not receive any nitrogen – will give a soil nitrogen supply figure, as the nitrogen taken up by the barley crop will only have come from the soil.

Leaf samples will be taken throughout the season and crop yield and protein content will also be calculated at the end of the trial.