BRENDON CANT brendon at iinet.net.au
Wed Mar 11 02:17:04 CET 2009



Applying ‘insurance’ dressings of nutrients in case the paddock is
responsive can be very wasteful of fertiliser dollars, says Dr Bill Bowden
of the Department of Agriculture and Food WA (DAFWA).

For example, applying a nitrogen/phosphorus/potassium compound to a whole
paddock when only 25 per cent of the area is responsive to potassium,
represents wasting money on potassium on 75 per cent of the paddock.

Speaking at the recent WA Agribusiness Crop Updates in Perth, Dr Bowden,
recipient of the Grains Research and Development Corporation (GRDC) Western
Region Seed of Light Award 2009, for excellence in communication, spoke on
the topic of ‘Fertilising in a changing price environment’.

The Crop Updates, organised by DAFWA and supported by the GRDC, allow
researchers, consultants, grower groups and agri-business advisers to catch
up on the latest research and trial results.

Dr Bowden said that high fertiliser prices in the spring of 2008 presented
growers with the dilemma of spending two to three times more on fertiliser
or buying half to one third of their usual quantity.

He indicated this had the positive effect of forcing them to rethink their
fertiliser strategies and at the same time re-examine how fertiliser
expenditure fitted into the overall farm budget.

For example, profit can be insensitive to fertiliser rate when nutrient
levels are already high as a consequence of past fertiliser applications and
the soil is only marginally (less than 15 per cent) responsive to fresh

Dr Bowden stresses that diagnosing the nutrient status of paddocks and zones
within paddocks becomes increasingly important as grain and fertiliser
prices rise. Soil testing, precision agriculture and variable rate are
important technologies for finetuning efficiency.

And “playing the season” using split applications of nitrogen has become
standard practice. By not applying all of the nitrogen up front or at
seeding, growers can avoid over-fertilising if the season goes bad or may
put out more nitrogen if the season and crop are going well.

Dr Bowden also says that removing or ameliorating yield constraints which
limit crop uptake of water and nutrients – by techniques such as deep
ripping and liming – may be a better use of finance than spending on

Many growers think about nitrogen from legume break crops when fertiliser
prices rise, but they should also consider fallow which conserves soil
moisture and releases mineral nitrogen.

He says nutrients from organics products such as composts, animal manures
and biosolids are less concentrated than their fertiliser counterparts. So,
to be competitive, organic fertilisers need to be priced lower per unit to
remain competitive.

And lastly, unsubstantiated claims about new products are no more valid now
that fertiliser prices have risen – the arguments should have swayed people
before the price rises, Dr Bowden says.

During a 40 year career with DAFWA, Dr Bowden has been involved in
developing many decision support tools for growers, including NPDecide,
Niterite, NPDecide and Lime: Optlime.


The Crop Doctor is GRDC Managing Director, Peter Reading, Tel 02 6166 4500
Further Information: Dr Bill Bowden, Tel 08 9368 3333

GRDC REF:CDMar091.doc/Blumenthal100309

Brendon Cant & Associates
Public Relations & Marketing
Suite 5
4 Gugeri St
Claremont WA 6010
Tel 08 9384 1122

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