Focus has rapidly changed from calving to pasture management with the onset of April. As we near ‘magic day’, conversations surround fertiliser applications and how much has been applied to date.
ur fertiliser spreader was only surviving from application to application, with ever-increasing respite visits to the workshop.
There are only so many spot welds that can keep a machine going and we had to go shopping.
The easy option would have been to buy another conventional spreader, designed to handle granular nitrogen in it’s many bagged forms… but something caught my attention last year at a conference.
Is it possible to get a greater response from N with a lower application rate? This question has fascinated me since I first heard a conventional New Zealand dairy farmer called Miah Smith tell his story.
Twenty years of grass measuring, high stocking rates, 21-day rotations of ryegrass, 250kg of N — it all sounded familiar to me. But he managed to reduce his N usage by 50pc in one year through foliar application.
As I listened to him, I told myself, he is obviously making this up and is being paid handsomely for it. It sounded ludicrous. But the question hung in my head: who would pay a farmer to use less product? Nobody. I had to do some research.
Most N fertilisers are applied in solid, granular form to pasture. The granules break down and are washed into the soil, where they are transformed into nitrate that can be taken up by the plant root system.
With foliar fertiliser, the N is applied to the leaves of the plant as a liquid and is taken up directly through the leaves, bypassing the soil transformation step, making it a more efficient process.
Granular N, in the form of urea, is generally mixed or dissolved with water plus a compound called humic acid to make a foliar solution.
This can be done in an IBC or storage tanker before being applied to pasture with a standard sprayer.
Alternatively, the urea can be mixed, dissolved and sprayed in a purpose-built machine to avoid having to use an IBC.
While we were shopping for a fertiliser spreader we decided to buy a foliar spreader that mixes and dissolves the urea in one step. Not a cheap option, but the more research I did on foliar spreading, the more attractive the payback looked.
In Wales, an Environmental Improvement Plan (EIP) was carried out using foliar N on four large commercial dairy farms milking 180-550 cows.
A number of sites were chosen where foliar N was used alongside conventional fertiliser, with nutrient applications every 21 days between March and October.
Initially the project began with very low levels of N, averaging 70kgN/ha for the foliar trial plots in comparison to 250kgN/ha on the conventional.
The conventional plots grew on average almost 15tDM/ha, while the foliar plots grew about 1tDM/ha less with over 60pc less N.
For the third and final year of the programme in 2021, a slightly higher rate of N at 100kgN/ha was used in the foliar trial plots.
As expected the foliar application broadly matched the conventional in terms of grass DM production but with 40-50pc less N usage.
The trial also measured higher clover coverage on the foliar plots versus the conventional, potentially due to lack of clover suppression from granular applications.
This all sounds very encouraging, so what are the negatives with foliar N? Obviously the application method is different, and leaf has to be present.
Grass covers of 600-700kgDM/ha are required for foliar applications, equating to 10 days post-grazing during the growing season.
As with spraying any product, the time of the day is important for humidity to facilitate plant uptake. Dry, cool conditions are ideal. Early morning or late afternoon provide best conditions for spreading, when humidity is high.
Applications shouldn’t be carried out when it’s wet as the spray doesn’t remain on the leaf and uptake is reduced.
There is quite an amount of solid research to back up foliar N applications.
As N usage gets increasingly limited due to emissions and environmental impacts, the choice to move to foliar N is easier. More bang for your buck.
We have done two rounds of foliar applications and we’re happy with results so far. Our target this year is to use 25pc less N with similar or greater grass DM production.
It is difficult to see why Irish trials are not in progress. But then again, who benefits when farmers use less product?
Gillian O’Sullivan farms with her husband Neil near Dungarvan, Co Waterford