Top Crop Manager

Features Fertilizer Seed & Chemical
Practices reducing GHGs evaluated

One project measures impact of cover crops on succeeding crops applied with manure.

November 13, 2007
By Adam Hayes and Ian McDonald


22aThe Government of Canada is developing a system where the agricultural community
will have the opportunity to receive some financial payback for environmental
initiatives. It will soon be possible to earn credits, and hopefully some real
dollars, for reducing greenhouse gas (GHG) emissions or sequestering carbon
in the soil. For the past three years, the Greenhouse Gas Mitigation Program
(GHGMP) for Canadian agriculture has been evaluating and demonstrating practices
that Ontario farmers can use to reduce GHG emissions.

The program, funded by Agriculture and Agri-Food Canada, has sites across Ontario
addressing field crop and horticulture crop production practices that reduce
GHG emissions. The Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA),
partnered with the University of Guelph and the Ontario Soil and Crop Improvement
Association (OSCIA), have been demonstrating how to better utilize manure nitrogen
in field crop systems and how late season residual nitrogen or nitrogen from
late summer manure applications could be sequestered by a cover crop.

Other projects are looking at how strip tillage could be used to allow reduced-till
corn to be planted on clay soils and how the strip-till toolbar can be used
for several operations to better place nitrogen and speed the all important
timeliness of spring seeding. Some regional soil and crop improvement associations
are demonstrating nitrogen rates and application timing in spring and winter

The data from this past season is currently being analyzed and will be reported
in future editions of Top Crop Manager. Here are some of the highlights
from the first two years of the projects. The project to improve nitrogen use
efficiency on livestock farms had ten sites across the province in each of the
past two years. Beef, dairy, broiler and swine manure had been applied to the
fields. The maximum economic rate of nitrogen ranged from zero to 145kg/ha N
(zero to 130lb/ac N). Three of the sites did not require any side dress fertilizer
N to achieve most economic yields. The pre-side dress nitrogen test (PSNT) is
a key part of determining the appropriate rate of nitrogen to apply. In 2003
the PSNT did a relatively good job of predicting fertilizer N requirements,
but in 2004 did not do as good a job. The researchers are looking at the PSNT
to determine if there are ways of improving the accuracy of the test.

The cover crop project was set up on a number of sites in Perth, Oxford and
Middlesex counties. The project included annual ryegrass, buckwheat, oats, oilseed
radish, peas, fall rye and red clover. Treatments were set up to evaluate the
effectiveness of cover crops in the presence and absence of manure. The manure
was applied prior to seeding the cover crops in August following the harvest
of a cereal crop. For non-legume crops, manure application (with high plant-available
N) significantly increased cover crop growth by as much as two to three times
that achieved in the absence of manure. The amount of nitrogen present in cover
crop biomass was generally higher where manure was applied. Both oats and oilseed
radish demonstrated an ability to sequester up to 80 to 100kg/ha N in the above
ground biomass by early November. The legume (red clover and peas) cover crop
yields were generally not affected by application of manure. Similarly, the
total N content in legume cover crop biomass was not significantly affected
by manure application.

On a few sites, corn was planted the following year to evaluate the ability
of the cover crop to transfer the biomass N to the succeeding crop. Generally,
higher corn yields were observed where manure was applied during the previous
year; even when relatively high rates of fertilizer were applied. Corn planted
following a cover crop generally had a smaller yield response to added fertilizer
nitrogen when no cover crop had been established.

The fall strip tillage project was able to demonstrate that the system could
provide yields similar to a conventional tillage system. The project also demonstrated
that the precision toolbar could be used to apply side dress nitrogen to assist
growers in applying the most appropriate rate of nitrogen and during a time
when it was less susceptible to GHG emission losses due to denitrification associated
with soil N levels in saturated soils early in the growing season.

The horticulture OMAFRA staff partnered with researchers from Ridgetown College,
University of Guelph to demonstrate the benefits of nitrogen management in vegetable
crops and the use of cover crops to tie up soil nitrogen following harvest.
They are also looking at irrigation efficiency and fertigation.

The GHGMP program was intended as a demonstration program so resources were
not provided to monitor GHG emissions from the demonstration sites. The Ontario
program provided funding to Dr. Claudia Wagner Riddle, a University of Guelph
researcher, to take the information that was gathered from the sites and estimate
the GHG emission reductions for the best management practices demonstrated.
Using the rates and timing of nitrogen applied in the winter wheat projects,
nitrous oxide emissions were calculated. The project confirmed that 90lb/ac
of nitrogen was the optimal rate for current varieties. Nitrous oxide emissions
were less at that rate of nitrogen than at higher rates. Calculations of nitrous
oxide emissions from the livestock project showed that applying the maximum
economic rate of nitrogen to the corn crop reduced the amount of nitrogen left
in the soil after harvest and minimized the nitrous oxide emissions.

The Soil Conservation Council of Canada is administering the program nationally
and the Ontario Soil and Crop Improvement Association administers the program
in Ontario in co-operation with the Innovative Farmers Association of Ontario.

*Adam Hayes is soil management specialist,
field crops and Ian McDonald is applied research co-ordinator, field crop technology
for the Ontario Ministry of Agriculture, Food and Rural Affairs.