Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 1, 1999
Publication Date: N/A
Interpretive Summary: Jointed goatgrass (Aegilops cylindrica) is a winter annual grass weed that infests several million acres of winter wheat in the western United States. This weed is genetically similar to wheat and decreases crop yield, crop quality and land value. At the present time, no herbicide will selectively control jointed goatgrass in a growing cereal crop. Some of the nonchemical strategies for managing jointed goatgrass include growing continuous spring crops, planting competitive crop cultivars, increasing seeding rates, and using deep-furrow drills to seed wheat into soil moisture. One method of nonchemical jointed goatgrass control that has not been examined is crop planting geometry. It has been hypothesized that winter wheat planted no-till in a paired-row system will enhance crop competition compared to winter wheat planted in a no-till traditional constant row spacing. It has also been hypothesized that deep-banded nitrogen fertilizer will be 'hidden' from the weeds. In a two-year field study, jointed goatgrass reduced winter wheat yield similarly regardless of crop planting geometry. In the first year, jointed goatgrass reduced wheat yield 24% in the paired-row system and 20% in the constant row system. In the second year, wheat yield was reduced 32% by jointed goatgrass in both planting geometries. Although crop yield reduction by jointed goatgrass was similar in both geometries, winter wheat reduced jointed goatgrass spikelet production more in the paired-row system than in the constant row system. Also, information from this study on nitrogen uptake would suggest that deep-banded fertilizer is not 'hidden' from jointed goatgrass.
Technical Abstract: A 1984-85 and 1988-89 field study near Pullman, WA evaluated the effect of two winter wheat (Triticum aestivum L.) planting geometries on the growth of wheat and competition against jointed goatgrass (Aegilops cylindrica Host). Treatments included paired and constant row planting geometries of wheat and locations of jointed goatgrass within each geometry. No planting geometry by weed location interactions occurred at any harvest date for plant height, shoot number, leaf area, plant dry weight, and N uptake for either wheat or jointed goatgrass. During the 1984-85 growing season, when averaged over weed locations, N uptake data indicates that by heading, jointed goatgrass had taken up N that had been deep-banded between wheat rows located 25 cm from the weed. Winter wheat yields were not different in the paired-row and the constant row spacing geometry in a weed-free environment. Within each year, for both planting geometries, winter wheat yield reduction was similar for each jointed goatgrass location. In contrast, based on jointed goatgrass spikelets produced, wheat grown in paired-rows was more competitive against jointed goatgrass compared to constant row spacing.