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Title: EFFECTS OF HERBICIDES ON DIRECT-SEEDED GUAYULE

Author
item FOSTER, M
item Coffelt, Terry
item MAJEAU, G

Submitted to: Association for the Advancement of Industrial Crops Conference
Publication Type: Abstract Only
Publication Acceptance Date: 8/12/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Recent studies have shown that guayule can be successfully direct-seeded. An effective preplant or preemergence herbicide is critical for optimum stand establishment. Several chemicals must be tested on different soil types across the potential guayule growing region (Texas, New Mexico, and Arizona). Guayule seedlings grow slowly and produce about 1 cm top growth and 5 cm root growth two weeks after emergence. Therefore, the young seedlings cannot compete against the faster growing weeds. This study was designed to observe the tolerance of a direct-seeded guayule population to the following preplant incorporated herbicides: bensulide, DCPA, and pendimethalin. The experiment was initiated at The University of Arizona Maricopa Agricultural Center on May 14, 2002. The experimental design was a randomized complete block with four replications. Herbicide treatments consisted of single raised beds spaced 102 cm apart and 9 m long, treated with bensulide (2.2, 3.4, 4.5 kg ai/ha), DCPA (4.5, 9.0, 11.0 kg ai/ha), and pendimethalin (0.6, 1.1, and 2.2 kg ai/ha). Treatments were applied using a CO2-powered backpack sprayer with a single-nozzle boom (Teejet 8002 flat fan nozzle) delivering 300 1/ha at 172 kPa. The herbicides were incorporated to a 10 cm depth with one pass of a tractor-driven tiller. Conditioned guayule seed (selection AZ-2) was then planted 1 cm deep on each bed with a Gaspardo SV255 pneumatic planter. The seeding rate was 100 seeds/m. The study was sprinkler irrigated for 13 days, and maintained by furrow irrigation afterward. Evaluations were conducted at weekly intervals by counting seedlings in 1 m long subplots in each herbicide treatment. Maximum seedling emergence occurred 10 days after planting. There were little differences between herbicide treatments 13 days after planting. Seedling mortality was noted and was probably due to salt damage by the sprinkler irrigation. Sprinkler irrigation should be discontinued 7-10 days-after-planting to minimize this problem. The number of seedlings in the medium rate of pendimethalin (1.1 kg ai/ha) was not different from the control. This rate corresponds to the recommendations for cotton. The preplant herbicides tested have good potential for weed control in direct-seeded guayule.