Paul McIn­tosh talks temperature and how it helps mung bean de­vel­op­ment

Cooler weather de­lays flow­er­ing

Central Queensland News - - RURAL WEEKLY - PAUL MCIN­TOSH

ONE of these years it is go­ing to rain re­ally sig­nif­i­cantly in early Jan­u­ary and then ev­ery­one can plant what­ever they want in sum­mer crop choices and vex­ing ques­tions like “can I plant mung beans?” in early Fe­bru­ary will not be an is­sue.

Mungs, like other crops, ac­cu­mu­late heat units to gen­er­ate growth and age­ing.

So with a base temp of 10.5 de­grees, then you need about 600 day de­grees for flow­er­ing to be in full swing.

Add another 500 to 600 day de­grees for phys­i­o­log­i­cal ma­tu­rity (PM) which equals about 1200 day de­grees.

Not much dif­fer­ent to chick­peas – an in­ter­est­ing fact as well.

You ac­cu­mu­late these mile­stones of growth stage as this ther­mal time in­creases.

So what has all this to do with when or when not too plant to, on the cal­en­dar?

If we have a cool­ish end of sum­mer and even cooler au­tumn, it is go­ing to take longer for our mung bean plants to reach the flow­er­ing stage and even longer to phys­i­o­log­i­cal ma­tu­rity time.

Cooler con­di­tions with ad­e­quate soil mois­ture lead to a longer plant life and there­fore a longer pe­riod of time your mung bean crop needs to set pods and seeds to reach ma­tu­rity.

At this time of year for plant­ing for any of our re­main­ing sum­mer crop op­tions in south­ern Queens­land, a frost on An­zac Day would cre­ate a fair bit of havoc with your sum­mer crop try­ing to reach PM stage.

In pre­vi­ous years, plant­ing dates around now re­ally do need a frost-free pe­riod to at least the mid­dle of May.

Re­mem­ber we are bet­ting on a con­tin­u­ous warm en­vi­ron­ment with ad­e­quate soil mois­ture to pro­pel our favourite sum­mer legume through the var­i­ous growth stages.

So what can you do to as­sist your mung beans in reach­ing phys­i­o­log­i­cal ma­tu­rity as quickly as pos­si­ble?

Well you can have in­put into some things and then there are other un­con­trol­lable en­vi­ron­men­tal de­tails that you are at the mercy of, like fu­ture weather con­di­tions.

To­pog­ra­phy is a key el­e­ment and lower creek or river flat ground com­pared to north-fac­ing slopes will cer­tainly im­pact on your mung bean crop’s de­vel­op­ment speed and crop safety.

North-fac­ing slopes should de­velop more quickly of course, es­pe­cially when com­pared to the other side or a south-fac­ing hill.

So a good even strike is your first re­quire­ment and a plant­ing depth as shal­low as pos­si­ble would be im­por­tant from a well struc­tured and soft soil sur­face.

The last thing you want is a crust­ing soil sur­face in this late plant sit­u­a­tion.

Some pop-up starter fer­tiliser po­si­tioned at least two inches be­low and to one side of the seed­ing zone would be handy, to pro­vide that early and even flush of growth as a seedling.

I have de­bated about adding a lot of ni­tro­gen fer­tiliser in the root zone of this fu­ture mung bean crop and I must say the jury in my mind is still out on the need for this heavy nu­tri­tion rate to speed up the growth process.

Cer­tainly we would achieve more dry mat­ter pro­duc­tion and prob­a­bly more yield, how­ever if you look at speed of crop de­vel­op­ment with the ex­tra bio mass cre­ated by large amounts of plant avail­able ni­tro­gen and hope­fully some mois­ture, you may not achieve much PM ear­li­ness here in the trade-off.

You want noth­ing to slow the plant growth down and that may in­clude some post-emer­gent her­bi­cides.

So weed con­trol tim­ing needs con­sid­er­a­tion in this en­deav­our of try­ing to beat the on­set of frost or cool tem­per­a­tures in the au­tumn time.

By my reck­on­ing over the past 15 years, there have been at least three oc­ca­sions of early frosts in April some­where in south­ern Queens­land im­pact­ing on our late sown crops.

The risk is there, how­ever so are the re­wards of plant­ing our short and quick mung bean crop.

Do some as­sess­ment in your own coun­try, along with your mung bean ac­cred­ited agro to share the load.

PHOTO: PAUL MCIN­TOSH

IN THE PAD­DOCK: Mungs emerg­ing from a 2017 wheat stub­ble block.

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