Archive Article: 1998/01/17
Better nitrogen use on the cards
WAYS of getting more out of less fertiliser at lower cost to the environment were abundant at the Fertiliser Societys annual meeting recently.
Esa Tirkonnen, of Kemira Agro, accepted there were challenges such as reducing the 20% of urea which can be lost to the atmosphere if not immediately incorporated into the soil after application, particularly on chalky soils.
Different methods of nutrient delivery, including a combination of biological and chemical processes, were being explored. Slow and controlled release fertilisers, and nitrification or urease inhibitors, could considerably reduce nitrogen losses to water and air, while increasing fertiliser efficiency.
David Powlson, of IACR-Rothamsted, agreed gaseous losses predominate but direct leaching is possible with unusually high spring rain. For every 10mm of rain in the three weeks after application, there is an additional 3% N loss.
Leaky
New decision support systems will help match fertiliser rate and crop requirement more accurately in the future said Prof Powlson. And "record growers reasoning for fertiliser application."
New crop and soil diagnostic tests will also allow more finely-tuned advice. Models could also be used to plan less leaky rotations in which crops leaving a lot of residual N are followed by a crop to use it best.
Variable fertiliser application will cut nitrogen wastage and decrease residual soil nitrate in areas of poorer crop growth, said Prof Powlson. Establishing wetland buffer zones alongside rivers and manipulating drainage by blocking drains in cracking clay soils, were just two of his tips to reduce leaching.
He slammed those growers of the 10% of winter wheat acreage still getting an unnecessary 30kgN/ha in the autumn. "This is indefensible," said Prof Powlson. "A large amount will be going – literally – down the drain."