Published on 31/03/2022
That’s the advice from Nufarm technical specialist Cynthia Christie.
“Right back when we first launched it, the most common thing we heard from farmers who used it in autumn was ‘we were a month too late getting it on’.
“They still got a response, but they could see they would have got more if their timing was better.”
There was a marked increase in demand for ProGibb SG last spring. While this may have had more to do with difficult growing conditions than environmental considerations, Christie says increased interest in the product as a nitrogen mitigation tool could see orders increase again in coming weeks.
No matter what the motivation, the key to a good result in autumn depends on planning ahead.
Autumn applications differ from those in spring because grass growth patterns are reversed. In spring, daily dry matter growth is speeding up, but in autumn it is slowing down and that needs to be factored into the planning process, Christie says.
Pastures must be grazed no more than five days before application, however the best responses occur when applied within 0-3days of grazing. And a 21-day interval is recommended between application and grazing.
“March is the ideal month to start planning autumn applications. Those who use ProGibb in autumn say best results come from having that extra grass available in the second to last and last grazing rounds before the cows are dried off for the winter.”
In situations where farmers want to add ProGibb to their nitrogen mitigation tool kit, the essential first step is making sure their pasture is capable of a response, she says. “In other words, the nutrient balance has to be right.”
It’s also very important farmers understand that ProGibb should not be regarded as a complete substitute for N fertiliser: “We’ve seen what happens in this scenario. It doesn’t work.”
In the absence of any newly published data about strategic use of ProGibb to reduce the quantity of N used, however, she refers to what is known and has been repeatedly demonstrated with regard to this particular gibberellic acid formulation.
The first point is that its ability to increase pasture production by 30-50 per cent more DM per ha in just three weeks does not hinge on extra N fertiliser.
“Provided existing soil nutrient levels are sufficient to support plant growth, we’ve shown you don’t need to apply more N to achieve this extra growth response.”
There is an additive response when ProGibb SG is applied with liquid N, but the two responses are separate, she says.
The second point that has been clearly defined is that the herbage nutrient profile of ProGibb treated grass is very similar to, or the same as, that of non-treated herbage.
“So we know that the extra pasture growth stimulated by ProGibb utilises available soil nutrients the same way ‘normal’ pasture growth does.
”Put those two points together, and there is potential opportunity for ProGibb to enhance N use efficiency for existing soil N in pasture, without sacrificing DM yield.
The principle here is akin to that which applies to catch crops, as studied by the Forages for Reduced Nitrate Leaching (FRNL) project, namely, the faster and more actively a plant grows, the more soil N it absorbs to support that growth. Validation of this principle would make a great research project.
“If you’re growing 30-50 per cent more DM per ha, and the nutrient levels present in that extra DM have not been diluted by the increased daily growth rate, the logical assumption is that you are utilising existing soil nutrients more efficiently,” Christie says.
The proviso is that soils in ProGibb-treated pastures are not nutrient deficient in the first place, particularly for N, but this can easily be determined through soil or herbage testing, she points out. And that in itself is not a bad thing.
“Many arable farmers test their nutrient status frequently throughout the season, to make sure the fertiliser they apply is appropriate to crop demand. I’m not sure how many pastoral farmers would do the same. But the more informed farmers are about the N status of their pastures, across the whole year, the better they will understand the N balance on their farms.”
For more detail contact your local Nufarm territory manager.