Malheur Experiment Station Information for Sustainable Agriculture

Yukon^® Rates for Control of Yellow Nutsedge in Corn Grown in Rotations Followed by Onion

Joel Felix and Joey Ishida

Malheur Experiment Station

Oregon State University

Ontario, OR, 2007

Introduction

Yellow nutsedge has become a major crop production threat in many agricultural fields in the Treasure Valley of eastern Oregon. The gravity of this problem is especially noticeable when the land is planted to onions. Thus, development of effective yellow nutsedge control strategies is viewed by many as priority number one for researchers. Control of yellow nutsedge presents a challenge because of its ability to reproduce by rhizomes and tubers that can survive in the soil for 2-3 years. Research results at the Malheur Experiment Station indicate that millions of tubers are produced per acre each season in heavily infested fields (Shock et al. 2006). Successful control of yellow nutsedge will partly require development of elaborate crop rotation schemes that include multiple tactics including tillage, fumigation, and herbicides to destroy those pesky tubers. It has been reported that farming activities play a significant role in yellow nutsedge distribution in infested fields (Schippers et al. 1993). This study is a first step in testing products that will enhance yellow nutsedge control in rotations that include onions.

Materials and Methods

A field study was conducted during 2007 in a field heavily infested with yellow nutsedge along Hwy 201 near the Malheur Experiment Station, Ontario, Oregon. The study was laid out in a randomized complete block design with four replications. The study area was moldboard plowed during spring and disked twice before forming beds to facilitate furrow irrigation. Following soil analysis, a compound fertilizer to provide 120 lbs nitrogen (N), 30 lbs phosphorus (P), and 13 lbs sulfate (SO₄), 2 lbs zinc (Zn), and 1 lb boron (B) per acre was applied on May 4, 2007. The entire study was planted to Dekalb Roundup Ready^® corn hybrid 'DKC-51-39' at 26,000 plants/acre in 2007. After harvesting, the study area was planted to winter wheat as a strategy to provide competition to yellow nutsedge during 2008, and in the process reduce yellow nutsedge tubers. Herbicide treatments tested in 2007 are listed in Table 1.

Pre-emergence treatments (PRE) were applied on May 9, early post-emergence (EPOST) on May 29, and post-emergence (POST) on June 8, 2007 using a CO₂-pressurized sprayer fitted with EVS 8002 nozzles. The sprayer was calibrated to deliver 20 gal/acre at 40 psi. Plots were evaluated for yellow nutsedge control using a visual scale of 0-100 percent (0 = no control and 100 percent = complete control) on June 15 and 22, 2007.

Soil sampling for initial tuber quantification was done by taking five cores from each plot, each measuring 4.25 inches in diameter and 12 inches deep on May 14, after bed formation and application of the first irrigation. The soil cores were processed to recover yellow nutsedge tubers using the washing and sieving procedure. Fall soil sampling was done on October 4 and processed to recover tubers on October 17, 2007. The tubers from each plot were placed in a ziplock plastic bag and stored in a dark cooler at 40°F until they were counted and weighed. The study was furrow irrigated as needed to maintain moisture in the top 12 inches of the soil profile. The corn was harvested for yield on September 28 from 20 ft along the two center rows in each (2.5-ft by 40-ft total) plot.

Results and Discussion

The study area had a relatively uniform distribution of yellow nutsedge tubers/ft² at the initiation of the study (Table 2). There was no difference in corn yield between treatments except for the untreated control that had very low yield due to excessive weed competition (Table 3). However, there was a significant difference among treatments for the number of yellow nutsedge tubers at the end of the season. Sequential application of Yukon^® at 4 oz/acre EPOST followed by 4 oz/acre POST when corn was at 5-6 leaf collars provided the best yellow nutsedge control in this study. Not surprising, the untreated control had the highest number of tubers per plot whereas the plots treated with herbicides had lower densities. The final corn yield followed a similar trend, with the untreated control producing the lowest yield. There was no difference in yield among herbicide treatments.

References

Schippers, P., S.J. Ter Borg, J.M. Van Groenendael, and B. Habekotte. 1993. What makes Cyperus esculentus (yellow nutsedge) an invasive species? A spatial model approach. Proc. Brighton Crop Prot. Conf.: 495-504.

Shock, C.C., J. Ishida, and E. Feibert. 2006. Yellow nutsedge nutlet production in response to nutlet planting depth. Oregon State University Agricultural Experiment Station Special Report 1075:160-162.

Table 1. Herbicide treatments for yellow nutsedge control in corn, Malheur Experiment Station, Oregon State University, Ontario, OR.

^aNIS = nonionic surfactant.

Table 2. Number of yellow nutsedge tubers on May 14 and October 4 (initiation and conclusion of the study), crop injury, chlorosis, crop growth reduction, and yellow nutsedge control, corn evaluations on June 15 and 22, 2007, and final yield, Malheur Experiment Station, Oregon State University, Ontario, OR, summer 2007.

Table 3. Yellow nutsedge control on June 22, 2007 and corn response to Yukon^® herbicide at the Malheur Experiment Station, Oregon State University, Ontario, OR, 2007.

Means followed by same letter do not significantly differ (P = .05, Student-Newman-Keuls)

Mean comparisons performed only when AOV Treatment P(F) is significant at mean comparison OSL.

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