How do you achieve a bigger root system?

THE few early horror stories I am hearing about some screening levels particularly in our southern wheat harvest are fairly disturbing to say the least.

As we all know screenings over both 5% or 10% does lower the price per tonne of grain quite considerably and I would judge this cruel blow at the grain silos catwalk as one of the biggest banes for farmers in our 2012 wheat harvest.

I wore out quite a few screwdrivers investigating our cereals root development in many blocks around the region.

Endeavouring to provide a wheat quality with less than 5% screenings is going to be tough for many of our number.

I really do dislike screenings and most of us would assume that the mid to late growing time dry weather is responsible and nothing can be done to ease this pain.

This is true and is exacerbated by a dry finishing season. The challenge for next year is to reverse this nasty trend of small grain and also probably reduced hectolitre weight as well, by all means agronomic if able to.

The first parameter is variety chosen. When you compare varieties results from the NV trials plus your own local knowledge, there is no doubt about the fact that variety can have an impact on potential screenings.

They can all produce screenings, however some cultivars are at a higher risk than others. Yes, I realise that given some significant mid to late August rain like we experienced in 2011, we would not be facing these levels of small grain.

Without doubt, most preferred varieties are usually chosen on other attributes like yield, disease package, nematodes, maturity and standability and the thought of screenings does not get much of a mention, as we all assume it is going to rain at the right time.

Our remaining breeders tend to concentrate on bigger issues and this is way it should be, however it seems that as we appear to have a different problem each year, all attention is directed at this immediate past problems.

So cultivar or variety is a place to start for a reduction in those bad screening years like this one is shaping up to be. With the variety choice comes time of sowing and the ability of some cultivars to be able to adjust their number of grains per spikelet or unit area.

Of course if sowing a long maturing variety in July, expect some problems with not only just small grain. So I suspect that there will be tendency to wider rows next year, so as to endeavour to compensate with some late moisture availability at the growth stage Z 3, 1 or nodeing in the old descriptive terms. How effective this may be will depend on our water deficit levels at these critical times.

The other factor that seemed to impact on us this year is the fact of the soil going hard, after all the early rain in June and early July. I wore out quite a few screwdrivers investigating our cereals root development in many blocks around the region.

This hard soil facet really did limit our root growth and extension, plus the extreme cold conditions in mid July to early August, all compounded to reduce our below ground root growth into moist sub soil.

Many a time I pulled out a wheat plant and the root system was lacking in size.

Sure, we had little to no follow up rain in many areas to drive down our secondary roots and this lack of secondaries is now impacting on our grain size as well as reduced yield.

It certainly appears that zero till country with good stubble levels stood the test of this year and yet the cropping sequence of wheat on wheat does leave me unenthusiastic with diseases like yellow spot and crown rot abounding again this year.

What other agronomic factors could cause our screening levels or more precisely what could we do in a proactive sense to reduce these screening possibilities?

I have mentioned zero till, however that was a challenge with weed control at its hardest late last summer and many of us resorting to Kelly chains or even scarifiers for extra control on glyphosate resistant Barnyard grass or Feather Top Rhodes. We all recognise that zero till is the best farming system to employ, it is just a matter of utilising early weed control herbicides and your nutrition program needs early thoughts for rates, placement and timing.

With urea at $700 per tonne last autumn, it is for sure none of us were going to be guilty of over fertilising our winter crop with nitrogen, so as to develop a huge amount of above ground green plant material (which then ran into moisture stress issues) was not a major problem this last winter.

MAP is not cheap also at more than $1000 per tonne to be used as a starter fertiliser at planting, however the one big issue that we need to correct or help with, is to develop a bigger root system.

This may well develop from quality soil structures, no high sub soil constraints present like sodium or chloride, nutrient availability at surface and depth, and new product developments like Zinc Ammonium Acetate to name a few. So maximising of your particular varieties yield, is the short way of expressing the solution and for that you need to achieve the optimum seeding time, adequate nutrition levels of N.P.K plus Zinc and not over emphasise plants per square metre.

For me this provides further evidence that a split application of Nitrogen products has more credibility in its use pattern.

There is much more I could say on this whole subject, however everyone has slightly different capabilities and programs and yes, we really do need wheat or barley in our cropping systems, as they both are the kings of stubble.

The challenges still remain for winter cropping regimes and fortunately chickpeas have not had so many problems in the growing season, however we still really do need good ground cover for protection from our future erratic summer storms.

Topics:  paul mcintosh plant health

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