MANY years ago, a farmer friend asked when was the best time to plant mung beans.
Being in a dryland situation, my reply was after a significant midsummer rainfall event, which is not a complete answer so I added, in my helpful way, that the seeding operation needed to be completed 30 days before more than two inches of steady rain.
He was patient with these replies and believed I'd get to the crux of the matter eventually. It's a great question and my replies were not too far wrong with planting dates.
We are aware that, as you go south from Central to Southern Queensland and into NSW, the time taken for a mung bean plant to begin flowering can extend from 38 to 46 days from a midsummer plant date. After all, this can be planted, grown and harvested within 100 days and having a split planting date doesn't worry me if high cultivation percentages are involved.
Some researchers have argued high daytime temperatures (>40degC) will negatively affect flowering mung beans more than an average diurnal temperature above 33degC. Whatever temperatures are reached in your mung bean crop, they all need good levels of soil moisture at planting. For me, utopia would be a constant of around 28-30degC, which is not going to happen.
So if your average daily temps are above 33degC, especially at reproductive time, then flower shedding will increase dramatically. It will be even heavier if subsoil moisture is absent.
On the subject of subsoil moisture assessments, how well do you estimate your own paddocks? I have this two-inch wide hand coring auger that is three foot long and when assessing subsoil moisture levels, it is a simple but Armstrong method of just digging out the soil core down to the handle. I can then assess by feel and looks, quantity of moisture and any dry bands in the soil profile - much better than those steel push probes which usually "overstate" the subsoil moisture and don't fill me with confidence. If I'm going to be providing planting advice on mung beans, my assessment of moisture must be accurate.
From my experience, I will acknowledge that two feet of solid moisture or PAW (plant available water) on black Jimbour/ Mywybilla-type soil can yield 1.6 tonnes per ha, whereas three feet could yield over two tonnes per ha. If you only have a foot or so of partly-moist profile, you are lining up for failure (<0.7 t/ha), particularly in what we all expect is going to be a drier year.
Needless to say, our CQ farming cousins and the far Western Downs-type areas may not be able to achieve these sorts of average yields - no matter how good the consultant advice from Mr Spackman may be - due to these higher potential average temperatures in their extended summer period.
I will be the first to admit that mung bean growing is not for every- body or every paddock and, after due agronomic considerations, you should be selective in where this desirable rotation legume crop is placed in your farming system. Tempera- tures we can do little about but having a good moisture profile is a variable you can influence in the fallow period before a seeding date, whenever that is.
Marketing groups advise me the 2012-13 crop price is fairly strong and, as usual, sample quality is important.
So when contemplating a summer crop and your recent winter cereal block, with no residual herbicides applied, has moisture building up in it from some heavy storms, plus weeds like FTR and glyphosate- resistant Barnyard grass are a real problem, consider a short, quick legume crop like mungs.
But ensure you do your pre-plant homework, in conjunction with an accredited mung bean agro.
Paul McIntosh is former manager of Landmark Emerald, now based on the Darling Downs.
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