Enquiry from a customer regarding possible causes of slow pasture growth.
 
This follows our phone conversation of today.
 
Situation:
11 hectares affected by poor pasture growth.  2,4-D had been applied some weeks earlier.  75kg/ha urea applied the day before Decision was applied at 50g/Ha.  That was about 4 weeks ago.  The buttercups targeted by the Decision application had all been controlled normally and satisfactorily.  Paddock was locked up for silage.
 
Pasture grasses have however done poorly and remain only ankle high rather than the expected knee high.  The grasses have not actually died, but are doing very poorly in spite of decent growth conditions.
 
We’ve not had any report in the past of grass damage nor of growth suppression with Decision (flumetsulam).  There’s no chemical mechanism we’re aware of that would connect flumetsulam with pasture suppression, at any application rate.
 
Urea:
I’ve searched the available literature of other flumetsulam brands, both in NZ and overseas.  I haven’t found any published reports of undesirable interaction between flumetsulam and urea, nor any other fertiliser.  Nobody has published any cautions about it, and that includes both NZ and Australian regulatory bodies (ACVM and APVMA respectively).  I am pretty confident that these two substances applied a day apart is not a problem.
 
Cold Weather:
You mentioned that a farm supplies representative had said applying flumetsulam in cold conditions could lead to grass damage or slow growth.  I’ve seen no reference to that in the literature of any flumetsulam brand.  That’s not to say it’s impossible, but it can’t be a major issue or it would have come up before, either from within users of Decision or some other similar brand.  And it hasn’t.  Also, the herbicidal effect of flumetsulam is fairly short-lived except in highly susceptible species like brassicas.    So what I’m saying there is that any effect of cold weather application … if such an effect really exists … would have to be temporary.  Once the weather was better, growth should resume normally as long as the grass plants were still viable at all, I.e. not actually dead.  
 
Small Trial:
We're sending you a small pack of Decision at no charge so you can hand spray a bit of pasture that you judge to be reasonably similar to the treated area.  That way you can evaluate the effect on subsequent growth against an adjacent untreated section of the same pasture.  I'm confident that the effect will prove to be normal, with no check to pasture species, but it's worth doing if just to rule Decision out.
 
You also mentioned that you’d be testing the soil for fertility levels (about which you now had some suspicions), and that might be an explanation.  Would you please let me know the outcome of that, plus the small scale Decision trial spray?  And anything else that develops or occurs to you as well.  We’d like to help you to figure out what happened, so the more information the better!