Teagasc is strongly advising all tillage farmers to develop a nutrient management plan for their business, and the time to do this is now.
According to Teagasc’s Michael Hennessy, almost all tillage farmers would welcome organic manure to their farms as it adds extra nitrogen (N), phosphate (P) and potash (K) to boost soil carbon and will add resilience to the soil.
“However, there are a number of reasons why tillage farmers should be careful when importing organic manure for the coming year,” he explained.
“Every tillage farm needs to have a valid soil test in order to apply phosphate to any field.
“If a field does not, then it is assumed that soil is at P index 4, therefore no P is allowed to be applied.”
Nutrient management plan
Tillage farmers are aware how well nutrients are utilised on farm. The National Farm Survey data confirms a tillage farm nitrogen use efficiency of 70% or over and phosphorus use efficiency of well above 80%.
Therefore, there is little wriggle room for reducing or miscalculating the nutrients available to the growing crop, or yields will quickly be compromised.
From soil test results nationally, there are 23% of soils which are at soil P index 4. As a consequence, there is no allowance to import and apply organic manures to these soils.
All tillage farmers need to register with the Department of Agriculture Food and Marine (DAFM) on the new National Fertiliser Database. Failure to register will mean the farmer cannot purchase chemical fertilisers.
Over the coming weeks and months many tillage farmers will be asked if they would take some slurry or other organic manures onto their farm.
“There are deals to be done with intensive livestock farmers who will be under pressure to move organic manures,” Hennessy added.
“However, the tillage farmers must ensure that any organic manure transferred to them through the DAFM manure exports system, arrives on the farm with a good nutrient status.”
Cattle or dairy slurry can either be very liquidly or quite thick. The difference in dry matter between these slurries has a huge bearing on the nutrient content of the slurry.
The transport of slurries is expensive. But this becomes even more expensive when the slurry has a low dry matter content.
Rough calculations suggest, balancing the nutrient value in cattle slurry (4% dry matter) with the costs of transport and spreading, slurry will struggle to be economic if transported over 10km.
Nitrate loss
Organic manures, especially high N organic manures, applied to the soils in late summer or the autumn are prone to nitrate loss.
Losses of 10-15% have been recorded from these manures and this adds to the normal nitrate losses from free-draining tillage soils.
Planting a crop with a high demand for nitrogen like oilseed rape is recommended in these circumstances.
Nitrogen recovery by winter cereals is small and will not mop up excess nitrates from organic manure application.
The loss of these nutrients is not only harmful to the environment but will also reduce the farmer’s ability to purchase chemical nitrogen the following spring.
All organic manures should be applied ahead of a growth period in the spring to achieve a high utilisation of nitrogen.
“If tillage farmers intend to import organic manures, then they need to get a plan in place quickly,” Hennessy said.
“Firstly, ensure that soil samples are up to date. If not, these should be taken immediately.
“Secondly, farmers should book an appointment with their tillage advisor over the coming few weeks in order to get a specific nutrient management plan drawn up.
“Leaving all of this to the spring of 2024 may be too late,” he concluded.