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Are you considering cutting back on crop inputs?

Do cutbacks on fertilizer or herbicides make more sense?

November 15, 2007
By John Harapiak


A global over-supply has weakened the demand for feed grains and oilseeds.
Canadian prices are being pressured as a result of record corn and soybean crops
in the US. Fertilizer and fuel prices are currently at high levels and with
a Canadian dollar that has been swept into a significant upward spiral, per
acre crop input costs for 2005 are going to be of concern to prairie producers.

Low grain prices create pressures
Grain prices are currently at disturbingly low prices and this has placed some
farmers under a lot of financial pressure. As a result, quite naturally, some
will consider cutbacks in the use of some crop inputs. If cutbacks are to be
considered, what approach should producers take?

Research evaluation of input cuts
all inputs be cut back equally? Based on information obtained from 25 site-years
of data, Agriculture Canada researcher Stu Brandt, who is located at Scott,
Saskatchewan, does not think so. He studied the interaction between the use
of fertilizers, herbicides and stubble management (either fall-tilled or left
standing for snow trapping) on spring wheat yields. Based on the information
he collected from these trials, Brandt feels the message is very clear: be cautious
about cutting back on yield boosting inputs.


All soil zones included in trials
In the trials in question, the effect of stubble management, fertilizers and
herbicides used alone and in combinations were investigated. The number of years
at each site varied from four to nine years. The trials were located near Kindersley
(1983 to '86) in the Brown soil zone, at Scott (1983 to '91) in the Dark Brown
soil zone, at Lashburn (1983 to '90) in the Black soil zone and at Mervin (1983
to '86) in the Gray soil zone.

Pattern varies with moisture supply
Responses varied with years and sites, depending on moisture supply. However,
responses were similar for 20 site-years where the combined yield impact of
standing stubble, fertilizer and herbicide exceeded 25bu/ac of spring wheat.
When wheat yields were below 25bu/ac (primarily due to drought), responses followed
a different pattern. For this reason, the results were grouped and averaged
for the high and low yielding site-years (see Table 1).

Table 1. Response of spring wheat (bu/ac)
to crop management treatments including standing stubble, application of
fertilizer and herbicides. Agriculture and Agri-Food Canada Research Station,
Scott, Saskatchewan.
High yielding sites Low yielding sites
Management treatment Yield (bu/ac) Increase (bu/ac) Yield (bu/ac) Increase (bu/ac)
Fall tillage, no fertilizer or herbicide 19.8 Zero 10.1 Zero
Standing stubble only 19.1 – 0.7 9.4 – 0.7
Fertilizer only 29.2 9.4 11.5 1.4
Herbicide only 24.9 5.1 14.4 4.3
Standing stubble plus fertilizer or herbicide 38.1 18.3 19.5 9.4
Note: Stubble was either tilled late
in the fall or left standing to increase snow trapping. Along with each
stubble treatment, N and P fertilizers and herbicides for both grassy and
broadleaf weed control were applied either alone or in combination. Treatments
also included a no fertilizer, no herbicide check. Fertilizer nitrogen was
applied at 40lb/ac of actual N and P at 20lb/ac of phosphate.

Combined benefit exceeded sum of individual inputs
As shown in the table, for the 20 high yielding site-years, standing stubble
reduced wheat yield by 0.7bu/ac, while fertilizer alone increased yield by 9.4bu/ac
and herbicides alone increased yield by 5.1bu/ac. If these crop input factors
functioned independently, combining them should have provided a yield increase
equal to the sum of the individual responses, or 13.8bu/ac. The actual combined
response was an increase of 18.3bu/ac.

Similar dry year trends
Responses to stubble treatment and herbicides were similar at the low and high
yielding site-years. Not surprisingly, fertilizer responses and combined responses
were much lower for the lower yielding sites, since fertilizer responses are
typically low in drought years. Despite lower fertilizer responses, the combined
response still exceeded the sum of the individual responses by 4.4bu/ac of spring

Returns maximized with good management
It is apparent from these results that the various crop management factors do
not function independently. Changes to one crop input will invariably influence
responses to others. The message we can take from these trials is the value
of a given management practice can usually be enhanced by ensuring that other
management factors are optimized. The fact that these wheat studies were conducted
over four soil zones and a number of years indicate that these results should
be broadly applicable to the prairie region. While the study was restricted
to spring wheat, the same principles should apply to other crops.

Yield building vs. yield protection
low grain prices, it is tempting to try to cut input costs and crop inputs are
often the target of this exercise. Brandt states that "While minor adjustments
to fertilizer rates, or moving to lower cost herbicides, may be justified, farmers
should be wary of making drastic cuts to any single input. Nowhere is this more
important than for inputs like fertilizer and quality seed for high yielding
varieties. These are the inputs that build a high yield potential. Other inputs
like pesticides protect that yield potential. The value of such inputs is diminished
where yield potential has been lowered due to cuts of yield building inputs."

Brandt indicates that making a significant cutback in fertilizer usage may
in fact be the worst decision to make. His point is that the use of fertilizer
helps to build yield potential. He emphasizes that producers should consider
building yield potential before thinking about protecting it!

Others seem to agree! Dr. John Martens, a chief economist with the 'Top Farmers
of America', has stated that maintaining fertilizer rates is the best way of
lowering per bushel costs of production.

John Harapiak has approximately 40 years
of western Canadian based fertilizer related experience. He will continue
to contribute stories to Top Crop Manager. He can be contacted by e-mail