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Boost returns by matching inputs to land productivity

...season-long push for higher yields...

November 19, 2007
By Helen McMenamin


32aA season-long push for higher yields may give you some impressive numbers,
but it probably is not the way to the best net returns says George Lubberts,
an independent agronomist at Nobleford, Alberta. "You may be better off
cutting back on inputs on some of your land," he says. "Returns vary
enormously across most fields and the worst areas may be costing you more than
they're worth."

Lubberts provides this example. For a five bushel difference between the best
and worst parts of a field, spending $20 to bring the poor areas up to the yield
of the best parts can be justified. But, very few fields have that small of
a variation. A 25 bushel spread is much more common. Bringing those areas up
to a decent yield is likely much more costly.

A yield map is the easiest way to define productivity for each part of a field.
But, infra-red satellite or aerial photographs work too, as can estimates of
yields by measuring grain combined in a set distance across good and poor parts
of the field or by hand-harvesting small areas.


Lubberts groups areas of similar production:

  • good – those giving close to target yields in a reasonable season;
  • excellent – more than 10 percent above the target yield;
  • poor – producing only half the target yield; and
  • very poor.

Next, Lubberts calculates a break-even analysis on each area; return per acre
(yield times price) minus the total inputs and fixed costs per acre. He uses
these figures to decide input levels for each area. If possible, he puts dollar
values to remediation measures.

"Often, it's not feasible to fix the problems causing very poor yields,"
he says. "Seed a perennial crop there and stop pouring inputs into areas
that will never give you a return. Even cutting your fertilizer to zero, those
places cost you money to farm. They're often the places where you break equipment,

For poor areas, he suggests half rates of fertilizer. "If yields vary
from 40 to 60 bushels in a reasonable year, why fertilize the whole field for
60 bushels? You can probably save $8 or $10 an acre overall by cutting back
in some places and applying at least your normal rate of N in better areas."

It is tempting to cut back seeding rates on poorer land, but germination and
emergence tend to be lower on poor land. It is best to seed at full rates and
monitor these areas before cutting back on seed.

Weeds are generally worst in poor crops, so low productivity areas are not
the places to cut back on herbicides. You may be able to shave rates in a vigorous
crop if you are spraying early when weeds are easy to kill. Spray full rates
in conditions that are not ideal for the chemical – Liberty in cool, cloudy
conditions, for example, or if you have any hard-to-kill weeds.

Careful scouting pays off, says Lubberts (who checks a lot of fields in his
business). Knowing how much of a field is affected by what and how many weeds,
insects or diseases, allows you to decide whether and where to apply crop protection

When you are considering whether to spray for insect pests, Lubberts cautions
that threshold numbers for insects are based on average to good crops. If you
are aiming high and your crop looks considerably better than average, you may
want to spray at lower insect numbers.

Heavy crops are the most likely to lose yield to disease. Lubberts advises
spraying fungicide only in these areas, but be prepared and treat as soon as
you see symptoms if conditions favour the fungus. "People tend to delay
fungicide treatment because of the cost," he says. "The price is less
painful if you know you're only spraying part of the field where it's worthwhile.
When conditions favour the disease, take some symptoms as a sign you're close
to maximum yield."

New software and rate controllers make prescription applications quite simple.
Or, you can focus inputs on the best areas of each field with a low-tech system.

"Be prepared to modify your plan once you get into the field," says
Lubberts. "And, don't expect perfect results. This is an ongoing exercise.
With each season's scouting and yield maps, you can refine your decisions and
modify your plan. I'm convinced though, that your bottom line will improve when
you start treating each part of your land the way it treats you." -30-