Take a whole soil profile approach
Nitrogen may be the most commonly considered grassland nutrient, but paying attention to the whole soil profile can be equally as important and could in many cases cut nitrogen requirements.
Soil structure seems obvious as the first place to start, but too often it is neglected, reckons consultant Jo Scamell.
“Promoting an aerobic soil crumb structure, rather like a honeycomb sponge, in the top 6-8in of the soil promotes aerobic respiration to maximise release of nitrogen and other nutrients.
“Over time soil becomes compacted by machinery, equipment and livestock.
So, although it won’t alleviate plough plans, slit aeration can help bring soil back to its normal structure and maintain nutrient balance.”
The better soil crumb structure, the more efficient nutrient cycling will be, she says.
Dr Scamell also advises paying particular attention to fertiliser ingredients with regard soil type.
“We need to increase awareness and encourage farmers to think of both product ingredients in addition to NPK units.
In many cases a blend may be more effective than a compound in balancing mineral equilibrium within the soil.”
The other point to consider in making the most of nitrogen is the levels of other elements, such as calcium, magnesium, potassium and sodium.
“For example, applying nitrogen to boost dry matter of grass will be ineffective when calcium deficiency predominates.”
Although she appreciates that some elements, such as sodium, are less critical for bulk grass production, the importance of these nutrients is vital when considering mineral balance and forage palatability.
“There is no point investing in expensive fertiliser to grow a product which cows will not eat.”
And, with higher fertiliser prices, David Munday of Creedy Associates says attention to muck management is a key factor in retaining as much nitrogen as possible.
“For maximum efficiency farmers must adjust bagged fertiliser according to what nutrients have been applied with slurry, as too much can upset grass silage fermentation.”
Where grazing grass is concerned a winter application of slurry can be beneficial, but care must be taken not to have too high a potash content, as it may upset the balance with magnesium, potentially causing staggers, he adds.
“Avoid particularly wet periods as well, as most will be lost through leaching.”
But for accurate analysis, Mr Munday advises sending muck to a lab.
“It has to be a representative sample, not from the corner of the slurry tank.
Ideally, sample while spreading, so once results have come back you can make an accurate decision about bagged fertiliser applications.”
Although nitrogen application must be cost-effective, Mr Munday recommends injecting in spring, as more nitrogen is retained in the ground.
“Injecting slurry also means losing less ammonia into the atmosphere.”
Where injecting methods are unavailable he advises using reverse splash plates to direct the slurry back down to the ground, rather than up, again preventing ammonia loss.”
But the real winner in improving nitrogen efficiency for grass grazing is clover.
“Good management of established leys with correct use of slurry can have a fantastic role in freeing up nitrogen availability.”
Dorset-based dairy producer Clyde Jones has already made considerable strides in reducing his fertiliser costs, having relied heavily on clover leys and dirty water.
“With testing we are aware of a deficit in late summer and early autumn so would use 100-110kg/ha of nitrogern, but only when necessary.”
