Tiller count vital to get best crop performance
Tiller count vital to get best crop performance
By Andrew Swallow
KNOWING your plant counts and tiller numbers this spring will be more important than ever, says leading agronomy and distribution company UAP.
Last autumns awful weather and variable establishment means few crops will perform to their optimum if managed routinely. All inputs will need careful matching to growth stage and crop density.
"You have got to get people out there counting plants and tillers at key times, especially this year," says southern region technical adviser Peter Gould. "And you need to assess crop vigour too."
At the core of his advice is canopy management. That term may have been overused, he acknowledges, but it is the most profitable approach. "It really is a way of getting more for less."
The ultimate goal is a Green Area Index (GAI) of five or six for the grain fill period. Even at that stage some soil will still be visible through the canopy.
Achieving that optimum canopy structure starts with seed rate set to produce a target plant count. But with most winter crops already sown, it is now a case of counting tillers on the plants that are there and tuning inputs accordingly.
Most important is nitrogen management, both in amount and timing. Crops that have over 600-700 tillers/sq m by early March should receive no early nitrogen with the aim of limiting tiller development to 1000/sq m by GS31.
That typically coincides with the terminal spikelet stage, when the main dressing of nitrogen should be applied. Over thick crops may be thinned by holding nitrogen back a week or so beyond terminal spikelet.
But that is a risky strategy, warns Mr Gould and growers must be prepared to get on with the nitrogen as stem elongation starts, even if it means making ruts.
"You can starve the crop up to a point, but there is a critical time when you must get on. Stem elongation causes a big demand for nutrients and if the plant has not got enough nitrogen it will abort grain sites."
In some fields losses due to unintentional delays have hit 2.5t/ha (1t/acre), he adds.
Where crops have less than 600 tillers in early March 40kg/ha (32 units/acre) of nitrogen should go on as soon as possible, followed by the main dose 10-14 days before terminal spikelet stage. For very late drilled crops that early nitrogen should be brought forward to mid-Feb where crops are struggling.
Many later drilled crops will not have been rolled and that should be done as soon as conditions permit to provide anchorage for the crown roots, says Mr Gould.
An application of Meteor (chlormequat chloride + choline chloride + imazaquin) mixed with straight chlormequat for forward crops, or Route to boost rooting for backward crops, should go on at GS30, with a follow-up pgr at GS31-2.
"Place the rule in the row, count plants and tillers, and read off on the chart," says UAPs Peter Gould. Such information will be vital for managing the variable state of crops this spring, he believes.
BUILDING GAI 5-6
BUILDING GAI 5-6
BUILDING GAI 5-6
• Target plant population by drilling date.
• Manipulate tillers with N and pgrs.
• Calculated N applications.
• Fungicide management – strobs essential.