Blame it on the rain

A common misconception about how urea fertiliser behaves in moist soil could be affecting production on dairy farms.

Dairy farmers who have been experiencing wet weather could be facing unexpected soil nutrient loss due to a common misconception about how urea fertiliser behaves when soils are moist from previous rainfall events.

This misconception is based on a common belief that volatilisation – the process where nitrogen is lost through conversion into ammonia gas – is minimised if urea fertiliser is applied to moist soils or before a heavy dew or light rain.

Ballance Agri-Nutrients Science manager Aaron Stafford says that a strategic look at your nitrogen fertiliser applications and some smart science can help get the best from your investment, rain or shine. “Just because it is been wet doesn’t mean volatilisation from urea will be negated. Contrary to popular belief, nitrogen losses actually increase with increasing soil moisture,” says Stafford.

“This is because urea fertiliser is rapidly converted to ammonium, especially when applied to moist soil. And once in the ammonium form, nitrogen will be retained close to the soil surface and will not be washed deeper into the soil with subsequent rainfall, therefore increasing the amount of nitrogen available to be lost through ammonia volatilisation.”

This unexpected loss of soil nutrients could seriously affect production on dairy farms, with many dairy farmers – feeling the squeeze from low international milk prices – cutting back on imported supplementary feed and relying on pasture production as a cost-effective alternative.

“By using products from within Ballance’s SustaiN range, which include the world leading Agrotain™ nitrogen stabiliser to minimise ammonia volatilisation, farmers can negate the effects of ammonia volatilisation and increase the amount of nitrogen available to grow more grass,” says Stafford.

Stafford cautions it is also possible that farmers affected by higher than average rainfall, particularly those on free draining soils, will have experienced high sulphate leaching in their soils over winter. Soils with low soil sulphur levels have the potential to limit pasture responses to nitrogen fertiliser in the early spring period, lowering overall growth. This can be overcome by switching from a nitrogen-only product to a product that combines nitrogen and sulphur, such as SustaiN Ammo or PhaSedN QuickStart.

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