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Is it too late for N?

Perspectives from the Northern, Southern and Western grain growing regions, September 2014.

South

Chris Sounness, Birchip Cropping Group.

In the southern region the condition of the crops in late 2014 is diverse. Struggling, almost unharvestable through some areas of the southern Mallee in Victoria, to looking very good through some parts of SA and Southern NSW. Late application of Nitrogen is only really an option for crops with very high potential, soil profile is very moist to depth and there is confidence surrounding September and October rainfall.

The rule of thumb is the later nitrogen is applied in the season the greater the contribution to protein % over yield. There is little evidence to show positive economic returns from chasing protein in low to medium rainfall environments.

In the high rainfall zone where crop are still before flag leaf, extra N can be profitable with earlier applications coming through as better yield and later applications possibly raising protein. A good guide to the N status of the crop is to look at the oldest leaves (canola) or tillers (cereals) – if they are green then N is not likely to be limiting.

BCG have done trials over the last three years looking at applying late season Nitrogen in low and medium rainfall environments to Barley. To increase grain protein by 1% an extra 10kg/ha of urea is required for every tonne of crop expected.

Trial results are found on the following links 2012 trials, 2011 trial 1, trial 2.

North

Chris Dowling, Back Paddock Company.

It is generally too late for N application to winter crops in the northern grains region
of Australia (apart from some of the later crops that will be irrigated between second
node and flag leaf emergence).

With the diversity of climatic areas in the north crops are currently from the second
node through to maturity with the majority rapidly approaching flag leaf. Therefore
they are rapidly changing from extra N producing yield to extra N producing grain
protein. For those crops at the flag leaf stage and beyond (doing the maths with
current grain and fertiliser prices and seasonal conditions) it is unlikely to be economic to apply N now.
This goes for either foliar sprayed or soil applied N.

Growers are reminded that an important step in planning for the next crop in a
paddock is to do post-season review. Generally, where cereal crops have produced
less than 11% protein, N is likely to have been more limiting than water in this season.
A little more N would likely have increased yield and there is little likelihood of
a carryover of mineral N in the soil profile for the next crop. In low protein areas
starting soil N will largely depend on the soil organic nitrogen stocks.

Where grain protein has been more than 12%, water may have been more limiting than N. Without a significant loss of N over summer, residual N in those paddocks could be and would need to be taken into account for the next crop.

West

James Easton, CSBP.

Nitrogen is likely to limit many crops in Central and Southern areas where yield potential is high.

Stripping from unevenly applied granular nitrogen fertilisers has highlighted the higher than normal demand for nitrogen this year.

Canola crops look to particularly affected – especially where following on from cereal plantings in 2013. There is only limited data on how late we can go with nitrogen top ups on canola, but a trial on 100% flowering hybrid canola crop last year showed that late applications can be very profitable – if the crop is N deficient.

Many Southern areas have had very good September rains, and the prospect of worthwhile responses to late N on high potential canola crops will have improved.

Late applications of N to cereal crops at Flag Leaf (Z39) and beyond have produced inconsistent results, and for most crops it will be too late to do anything this year. A late nitrogen application in cereals might still be applicable to parts of the Southern Ag region in WA, but for most areas the warmer temperatures (particularly up North) and dry soil profiles means it’s not worth it.

Late N can help increase grain protein content above 10% to help realise a price premium. Typically, the cost of the extra nitrogen required to increase protein is too large to be recovered through the price premium the grower would receive from a higher paying grade.

Bear in mind that for areas with relatively high soil organic carbon (2% or higher in the top 10cm) there could be enough mineralisation in the system to supply extra N and mitigate the requirement for an application.

If you do decide to go for it apply test strips as a decision aid for future reference.

Acknowledgements

Technical input from Jeff Kraak, Fertilzers Australia, (southern), Kaara Klepper, QDAFF(northern) & Liam Ryan, DAFWA (western), and Rob Norton, IPNI. Photo courtesy of Rob Norton, IPNI.

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