Strange things go­ing on in soil profile around re­gion

Warwick Daily News - South West Queensland Rural Weekly - - Front Page - PAUL MCIN­TOSH

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.

Imag­ine what your chick­pea roots think of it, look­ing for mois­ture and ab­sorb­ing these el­e­ments in high amounts.


A chick­pea field show­ing dead ar­eas sur­rounded by per­fectly healthy plants.

TOUGH CON­DI­TIONS: An oth­er­wise-healthy chick­pea plant show­ing plenty of brown leaves to­wards the bot­tom.

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