Strange things going on in soil profile around region
MY PHONE has run hot in the past few weeks with queries about our chickpea crops showing plenty of dead leaves etc.
Of course, many blame the herbicide regime or some disease or a plethora of virus issues not seen before.
However, being so dry, it is hard to imagine having a isoxaflutole residual product be able to work its way into the root zone of our developing chickpea crop, unless the cardinal sin has been committed with either leaving open seed trenches and/or achieving a very shallow planting depth, with some heavier-type rain soon after the herbicide application.
Yes, that can happen and has done in past years.
I would like you to look at the first photo above of an upper part of a single chickpea plant and observe plenty of brown lower leaves, and in the second photo consider the many dead plants with fringe areas of completely healthy ones.
The single-plant photo has been pulled from a paddock in the South Burnett that has subsoil constraints. The whole paddock has been affected in
this current chickpea crop to some degree.
Let me tell you the actual soil test amounts from some of the levels in this 0–30cm test range taken in crop, which should start your eyeballs twitching.
The ECdS/m is 3.0, magnesium percentage cations is 40.3 and if that is not enough, then chloride levels – in this top 30cm only remember – is 480mg/kg.
Sodium percentage is only 6.0 thank goodness and that is borderline for sensitive chickpeas.
It is a reasonable assumption that all these levels would go higher if we tested deeper cores, which could even inflict heavier growth and yield penalties as the crop progresses.
Imagine what your chickpea roots think of it, looking for moisture and absorbing these elements in high amounts.
I would say it is fairly reasonable to have a few brown leaves on the branches.
Not disease and not herbicides, and well done to the agronomist in Wayne Seiler from BGA who performed both soil and tissue tests in this dry winter season of 2017 to find out the real reason for brown leaves and non-performing plants.
Have a look at the second photo, where we have heaps of sick and dead plants with
the fringes of the photo having very tall and healthy chickpea plants.
So are there herbicide or disease issues here?
This photo was taken on the Western Downs in 2015, which, as we know, was as dry as a chip – no rain at all from planting to harvest time in many situations.
This phenomena for some reason was due to very high levels of sulphur that somehow naturally occurred in this paddock.
Never seen before, when the old attending agronomist did the 0–20cm soil test, it came back with 2200mg/kg levels.
That is extremely high and no wonder the chickpea plants died in this zone, and yet 15cm away the plants were as healthy as any I have seen.
Now the paddock was dotted with these distinct circular dead patches, yet the other 90-odd per cent of the block was very healthy and yielded well.
So do not just assume it is herbicide or a disease.
You might just consider taking a soil test in those upper root zones to determine if any soil constraints are to blame for the problem, especially if you have no current soil test or even a fairly useless 0–90cm one.
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Imagine what your chickpea roots think of it, looking for moisture and absorbing these elements in high amounts.