The Influence of Fertilizer Placement on Crop and Weed Ecology in Direct-seeding Systems
Assess the impact of fertilizer placement on weeds in no-till seeding systems.
IPNI-1996-CAN-MB9
21 May 2001
2000
Agronomic responses to fertilizer placement and reduced herbicide rates were evaluated at Brandon, Manitoba; Melfort, Saskatchewan; and Beaverlodge, Alberta in 2000, the last year of a 5-year study. The objective of the research was to evaluate spring wheat and canola responses to N fertilizer placement and herbicide rates in a no-till canola-wheat rotation. Many of the crop responses recorded in 2000 were similar to those observed in previous years at each location, as well as across the three locations. Variation observed in crop establishment with N fertilizer placement was seldom reflected in final grain yields, indicating that large differences in crop stand are required before the final yield of spring wheat or canola are to be influenced. Crop yield was influence by fertilizer timing and placement, with results varying year to year and location to location. For example, yield was frequently reduced in the wide row spacing treatment at Brandon, especially for wheat, but not at other locations. Fertilizer timing, fall vs spring application, did influence grain protein in many instances, with improved protein with spring application indicating that there were some over-winter losses of N from the system in some years at some locations. Neither fertilizer N placement nor herbicide rates in the study influenced crop water use. In fact, the lack of many significant crop development or yield effects due to herbicide rates used in this study indicates that reducing herbicide rates was of little agronomic importance.
The response of weed densities to fertilizer treatments and herbicide rates in 2000 confirmed data from other years. Reducing herbicide rates over the five years of the study had little cumulative effect on weed seedling densities at the time of in-crop spraying, despite occasional higher densities in previous July counts. In general, the seeding systems with fewer weeds at the time of crop establishment were the side and fall banded treatments. When differences occurred between the narrow and wide row spacing, the wide row spacing was weedier likely due to the higher row concentrations of nitrogen adversely affecting crop competitiveness. Similarly, when differences occurred between the sweep seeding system and other treatments, the sweep treatment was always weedier, in this case due to seedbed and nutrient availability issues.