Saturday, 15 July 2006

Long-term Effects of Fertilization and Crop Rotation on Soil, Water and Air Quality.

Craig Drury1, Dan Reynolds1, Chin Tan1, Don W. McKenney2, and Edward G. Gregorich1. (1) Agriculture & Agri-Food Canada, 2585 County Road 20, Harrow, ON N0R1G0, Canada, (2) Univ of Windsor, Windsor, ON N9B3P4, Canada

Corn yields, soil organic carbon (SOC), and CO2 and N2O emissions were recently measured over a four-year period on long-term cropping treatments established in 1959 on a Brookston clay loam soil in southwestern Ontario. Treatments included fertilized and not-fertilized continuous corn, and fertilized and not-fertilized rotation corn (corn-oats-alfalfa-alfalfa) with each phase present each year. Crop rotation increased corn yields and SOC contents relative to continuous corn. Emissions of CO2 and N2O were measured in the corn phase and were found to vary among treatments, with time of year, and across years. Averaged over 4 years, CO2 emissions were 50% greater from the fertilized rotation corn treatment than from the fertilized continuous corn treatment. The CO2 emissions from the fertilized continuous corn treatment were almost twice as high as those from the unfertilized continuous corn treatment whereas the fertilized rotation corn had 20% greater CO2 emissions than not-fertilized rotation corn. The 4-yr average N2O emissions were 88% greater from the fertilized rotation corn treatment (4.94 kg N/ha) than from the fertilized continuous corn treatment (2.63 kg N/ha). Twice as much N2O was emitted with fertilized continuous corn than with not-fertilized continuous corn (1.32 kg N/ha). Hence, both fertilization and crop rotation increased CO2 and N2O emissions in the corn phase.

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