Wooster, Ohio
February 26, 2007
Knowing a soil’s nutrient levels
increases options for fertility management and can help maintain
productivity in a continuous corn operation.
Robert Mullen, an Ohio State
University Extension soil fertility specialist with the Ohio
Agricultural Research and Development Center, said that a simple
soil test can reveal all that a grower needs to know about a
field’s condition, which can lead to smarter fertility
management and potential alternative options.
“One of the biggest issues facing growers under continuous corn
production is the increased amount of nitrogen use – generally
40 pounds more than in a corn/soybean rotation – and the higher
costs that come with using commercial fertilizer,” said Mullen.
“Growers are looking for ways to not invest in as much nitrogen
or to cut corners with other crop nutrient requirements. Pay
attention to soil tests. The quality of the crop is a function
of the operation of the soil.”
Soil tests measure the level of nutrients, such as phosphorus
and potassium, as well as the soil pH. Though nitrogen is an
expenditure that must be made every year on a corn crop, growers
have the ability to adjust their phosphorus and potassium
levels. By knowing those levels through soil testing, growers
under continuous corn production can effectively budget
fertility rates, said Mullen.
“Phosphorus and potassium are nutrients that don’t deplete every
year, like nitrogen. If the soil has an adequate level of
phosphorus and potassium, you don’t need to add more. Then that
money can be used toward the investment of more nitrogen,” said
Mullen. “Additionally, growers must keep in mind that excess
phosphorus can be an environmental hazard in the form of
run-off. So maintaining proper levels of phosphorus in the soil
is important.”
Soil tests can also come in handy to identify the pH of the
soil.
“Nitrogen fertilizer is a soil-acidifying reaction, so growers
might think about liming more frequently to maintain the pH at
around 6,” said Mullen. “A soil test will tell a grower the soil
pH and whether he needs to lime. If the pH is fine, then you
don’t have to lime.”
If budgeting for additional commercial fertilizer is not an
option, Mullen said other alternatives might exist with regard
to fertility management.
One option is manure application.
“If you have access to it, manure is a really nice resource of
nitrogen, potassium and phosphorus,” said Mullen. “Manure can be
used to offset some of the commercial nitrogen fertilizer costs.
It’s just a function of knowing how much to add to the soil.”
Mullen said that even with manure application, soil tests are
important.
“You can oversupply a field with nutrients that it doesn’t need
or can pose environmental problems,” said Mullen. “Knowing what
fields need the manure – not just spreading the manure on the
fields closest to the barn – is an important aspect of fertility
management.”
Additional OARDC research on fertility management includes:
comparing phosphorus and potassium fertilization between a corn
after corn rotation and a corn/soybean rotation; analyzing
nitrogen rates among different corn hybrids; the use of cover
crops in crop rotation; and improving manure management.
Mullen recommends that growers conduct soil tests either in the
fall or spring after corn or soybeans, or in the summer after
wheat harvest. The key is to be consistent about the time of
sampling when soil samples are collected. For example, if a
grower has historically sampled in the spring, then continue to
follow that routine.
For more information on managing a continuous corn rotation, log
on to OSU Extension Agronomic Crops Team Web site at
http://agcrops.osu.edu. |
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