Top Crop Manager

Features Agronomy Fertility and Nutrients
Use soil testing to balance crop nutrient requirements

November 20, 2007
By Donna Fleury

Keep your bank account balanced to maximize yield potential and minimize nutrient losses.

Optimizing nutrient management helps farmers improve the economics and profitability
of their cropping operations. Using tools such as soil sampling and soil testing
to balance crop nutrient requirements is becoming more important, particularly
as fertilizer prices rise. Applying fertilizer or manure nutrients based on
history or budget limits will not help producers improve profitability.

"I like to compare nutrient management and crop growth to a bank account,"
explains Len Kryzanowski, nutrient management specialist with Alberta Agriculture,
Food and Rural Development (AAFRD). "Soil testing and soil sampling help
provide a measure of the nutrient account in your soils."

Like a bank account, to make a withdrawal you need to know what is in the soil
and how much needs to be added before a nutrient withdrawal can be made by the
crop next year. By ensuring you have the right amount of nutrients, you can
avoid under or over-supplying the crop.


"However, unlike a bank account, the soil is a very poor way to save your
excess nutrients," says Kryzanowski. "Over application of nutrients
results in too many 'service charges', such as losses due to denitrification,
leaching and surface runoff. Every time you lose a nutrient to air, water or
soil processes, it is another unrecoverable loss in terms of yield potential
and potential revenues." Environmental concerns, combined with economic
optimization, mean that producers must balance crop nutrient requirements with
applied nutrients from fertilizer and manure, and that mineralized from the
soil. Producers must be able to account for nutrients in their farm operation.

"Keeping the balance of nutrients as close as possible to what you are
removing with the crop helps realize the yield potential or yield possibilities
you were hoping to achieve," says Kryzanowski. Optimizing nutrient management
is also depending on agro-climatic conditions, soil moisture levels and economics.
"With fertilizer prices on the rise and accounting for between 10 and 40
percent of input costs, it's important for producers to optimize their nutrient
management in relation to crop selection, expected crop prices, soil nutrient
levels and moisture conditions. As fertilizer prices rise, manure sources are
going to be a viable alternative to fertilizer nutrients, such as nitrogen and
phosphorus, and can be used to offset some of the fertilizer requirements."

Figure 1. Individual field results.

Producers are encouraged to do as much soil testing as possible, as timely
information improves nutrient management. "Some producers may choose to
pick a representative number of fields to sample every year, and by sampling
every field at least once every three years you are probably getting a fairly
reasonable picture of what nutrient levels are on the farm," says Kryzanowski.
For some nutrients, such as phosphorus, potassium and some of the micronutrients,
those numbers do not change too drastically unless some huge changes are made
in cropping practices. However, nitrogen levels can change drastically depending
on the crop year and may require more frequent sampling. If major changes are
made in cropping practices, or in weather-related conditions, it would be wise
to soil test more often.

Soil testing is also important for producers using manure in their crop production.
"Soil testing every three years is probably a good practice to follow,
unless more intensive manure application is being used," says Kryzanowski.
"If you are applying heavier rates of manure application, then more intensive
sampling will probably be required. The method of manure application can also
greatly affect losses. For example, if you aren't able to incorporate very quickly,
then you can lose more nitrogen than you think you are." Producers using
manure nutrients need to be aware of the Agricultural Operations Practices Act
and follow all regulatory guidelines, including the guideline for residual amounts
of nutrients that can be present in the soil.

Software programs help optimize nutrient management
There are several soil laboratories that can complete a proper soil test to
provide nutrient recommendations and an expected yield potential. AAFRD offers
some nutrient decision software tools, both for fertilizer nutrient management
and manure nutrient management. One tool for making fertilizer decisions is
a software package called AFFIRM (Alberta Farm Fertilizer Information and Recommendation
Manager). A new revised version was released in 2005.

"The software requires soil test results and can handle the results from
any of the different soil laboratories," explains Kryzanowski. The new
version goes beyond analysis at the individual field level and allows farmers
to wrap up the information for all of the fields into a whole farm type analysis
and optimization. Farmers can use it to help allocate their fertilizer dollars
to the right crop or field.

Figure 2. This new version of AFFIRM allows the
user to decide which field should receive what fertilizer based on the fertilizer

"It's important to remember that AFFIRM, or any other software, is a tool
to help make decisions, it does not make the decisions for you," cautions
Kryzanowski. "The farmer still has to make the ultimate decision for himself.
But the benefit of the software is it allows you to ask the 'what if' questions,
such as what if you change crops, or price, plus it allows you to take the moisture
conditions and growing season precipitation into account." AFFIRM is specifically
designed for fertilizer recommendations. For producers using manure nutrients,
the Manure Management Planner software is available to help with decisions.
Both software tools are available from AAFRD's web site, 'Ropin the Web', and
are listed under the 'Calculator' section of the web site.

Balancing crop nutrients is key to maximizing yields and minimizing environmental
impacts. "If you are over-applying nutrients, or the crop isn't taking
up all of the available nutrients, then you are making an environmental impact
either on the water, soil or air quality aspects," says Kryzanowski. "The
bottom line is, once you lose those nutrients you can't ever get them back for
crop production." Using tools such as soil sampling and soil testing helps
balance crop nutrient requirements, optimize fertilizer and manure nutrient
management and maximize returns and farm profitability. -30-



Stories continue below