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Nitrogen Fertilizer, Manure, and Compost Effects on Weed Growth and Competition with Spring Wheat

Agric. and Agri-Food Canada, Lethbridge Res. Cent., P.O. Box 3000, Lethbridge, AB Canada T1J 4B1

View larger version (36K): [in a new window]   Fig. 1. Weed shoot N concentration response to N source in four consecutive years. Common lambsquarters data were not collected in 2001 due to insufficient plants being present in the plots. Bars on the graph within a weed species and year with the same letter are not significantly different according to Fisher's Protected LSD test at the 5% probability level.

View larger version (56K): [in a new window]   Fig. 2. Wheat shoot N concentration response to N source in four consecutive years when grown weed-free or weed infested. Bars on the graph within a weed treatment and year with the same letter are not significantly different according to Fisher's Protected LSD test at the 5% probability level.

View larger version (53K): [in a new window]   Fig. 3. Weed biomass response to N source in four consecutive years. Bars on the graph within a weed species and year with the same letter are not significantly different according to Fisher's Protected LSD test at the 5% probability level.

View larger version (46K): [in a new window]   Fig. 4. Weed biomass response to N application timing–tillage intensity in four consecutive years. Bars on the graph within a weed species and year with the same letter are not significantly different according to Fisher's Protected LSD test at the 5% probability level.

View larger version (45K): [in a new window]   Fig. 5. Effect of N source over four consecutive years on the weed seedbank at the conclusion of the 4-yr experiment. The grass weed seedbank was composed of approximately 80% wild oat and 20% green foxtail. The broadleaf weed seedbank was composed of approximately 55% wild mustard, 35% common lambsquarters, and 10% other species such as redroot pigweed (Amaranthus retroflexus L.) and kochia [Kochia scoparia (L.) Schrad.]. Bars on the graph within a weed type with the same letter are not significantly different according to Fisher's Protected LSD test at the 5% probability level.

View larger version (45K): [in a new window]   Fig. 6. Wheat yield response to N source in four consecutive years when grown weed-free, with grass weeds (green foxtail and wild oat), or with broadleaf weeds (common lambsquarters and wild mustard). Bars on the graph within a weed treatment and year with the same letter are not significantly different according to Fisher's Protected LSD test at the 5% probability level.

View larger version (43K): [in a new window]   Fig. 7. Wheat yield response to N application timing–tillage intensity in four consecutive years when grown weed-free, with grass weeds (green foxtail and wild oat), or with broadleaf weeds (common lambsquarters and wild mustard). Bars on the graph within a weed treatment and year with the same letter are not significantly different according to Fisher's Protected LSD test at the 5% probability level.

View larger version (54K): [in a new window]   Fig. 8. Wheat grain protein response to N source in four consecutive years. Bars on the graph within a year with the same letter are not significantly different according to Fisher's Protected LSD test at the 5% probability level.