Signpost tillage farmer Don Somers from Wexford, outlined to the Teagasc webinar last week that he is taking a multipronged approach to adjusting his fertiliser requirements for 2022.
Through a range of different options, he hopes to reduce his expenditure on fertiliser this season by around €12,000 based on current price levels.
Each nutrient is being assessed separately, but together they add up to a significant reduction in what might have been a very substantial increase in expenditure across the farm.
His adviser, John Pettit from Teagasc, said that there had been considerable progress in improving soil fertility in recent years, with average soil pH up from 6.1 to 6.6.
The average P test result has been increased from 3.6mg/l to 5.1mg/l and potassium level has been raised from 96mg/l to 126mg/l.
Don has catch crops in all land destined for spring planting to help capture carbon and minimise nutrient loss
The investment in these improvements cost Don €43/ha per year but it is expected that it will pay considerable dividends this year.
Don has catch crops in all land destined for spring planting to help capture carbon and minimise nutrient loss. These crops bulked up very well this backend, so it is inevitable that they have taken up quite a lot of nutrient that may now be available to this year’s crop.
John also commented that chopped and incorporated straw had visibly soaked up as much as 30kg of mineral N
Assessments suggest 2t DM/ha and an uptake of 60kg N/ha, according to John. While not all of this will be available in time for this year’s spring crop, he estimated that it could provide 10-12kg N/ha, so another slight reduction in the need for applied N.
John also commented that chopped and incorporated straw had visibly soaked up as much as 30kg of mineral N, which will require watching in those fields later this spring.
Don is set to use all tools and technologies available to him to reduce fertiliser use this year, while maximising its efficiency. This begins with soil tests on every 2ha, with the locations guided by yield maps that Don produced for the past three years.
These will then guide P and K application rates. He is GPS enabled, so he can target variable quantities within fields for single nutrients using prescription files.
But the first thing to fix is pH through lime application. Don sees this as paramount.
While his intention is to apply all allowable potash (still good value) he reckons that the P savings will equate to €3,660 across the farm
For P, he will apply zero on Index 4 areas, 75% of recommended rate on high Index 3 areas, low Index 3 and Index 2 zones will get offtake rates and Index 1 areas will get a rate above offtake, but less than the maximum allowed.
While his intention is to apply all allowable potash (still good value) he reckons that the P savings will equate to €3,660 across the farm.
His spring cereal ground will all get 125kg/ha of 10:10:20 – combined drilled – as well as 5t/ha of layers’ litter.
This will supply the balance of the P and K and a lot of the N. He estimates that this is saving him €270/ha and €5,400 on his spring cereal area.
Actions on nitrogen
Don said that he will use protected urea rather than SulCAN on all his winter crops, but will stick with SulCAN for spring cereals.
He estimates that this move will save him €39/ha on his winter cereals and €33/ha on his winter oilseed rape, giving him a €2,900 saving across his winter crops.
As well as the change of product, he intends to decrease all maximum rates. He will use 190kg N/ha on his winter wheat (on an N Index 2 site) and the same on his winter barley on N Index 1 land. Spring barley will get 125kg N/ha.
But as well as this, he intends to use his past three years of yield maps to set up his spreader to apply more N to the areas that have been yielding above average, with lower rates on the parts of fields that have been performing below par.
He clarified that this means the lower-yielding areas that do not have visible problems that can be fixed.
On oilseed rape, he will use the green area index (GAI) to map his crop canopy which will then be linked to his variable rate spreader to apply variable N rates to produce a GAI of 3.5.