Band and Broadcast Applied Herbicides on Sweet Corn · 1999/2000 January 2001

TABLE OF CONTENTS

Introduction

Herbicide weed control is one component of production agriculture. Available herbicides should be evaluated periodically to determine crop tolerance and the best product for the weed species present. The population of weed species can change over time, especially if the same product is used year after year. The more available herbicides we have to choose from can, in some cases, provide more consistent weed control and/or allow us more flexibility in our crop rotation.

Objective

The herbicide tests on sweet corn were conducted to evaluate different herbicides and/or rates of herbicides to determine effectiveness of weed control and level of crop safety.

Materials and Methods

1999 John Case: A CO2 plot sprayer mounted on a Honda ATV was utilized to apply both the band and broadcast herbicide applications. The broadcast applications were achieved by utilizing a 5 nozzle spray boom (18 inch spacing) which delivered 10.3 gpa utilizing XR 8002 TeeJet spray tips, traveling at 4 mph, with 28 psi of pressure at the CO2 tank. The band applications were achieved by utilizing a 3 drop nozzle boom (30 inches apart applying a 15 inch band) which delivered 15.5 gpa utilizing TeeJet 8002E spray tips, traveling 4 mph, with 28 psi of pressure at the CO2 tank.

Each plot is 6 rows wide (3 rows band and 3 rows broadcast) by 190 feet long, replicated 3 times. The herbicides and rate/A used are listed in Table I.

John Case Farm, Montrose, Colorado 1999

All treatments (except Treatment 9) were applied on April 10, 1999. The broadcast applications were done first and weather conditions at the start of herbicide application were: air temperature 38 F, relative humidity 80%, wind 0-2 mph, and clear skies. The weather conditions at the start of the band applications were: air temperature 46 F, relative humidity 30%, wind 0-5 mph mostly 0-2 mph, with clear skies. All treatments were shallowly incorporated after all herbicide applications had been done utilizing a 4 by 4 foot chain harrow pulled behind a Honda ATV. Eradicane (Treatment 4) was incorporated first with a culti-packer with the teeth down, followed by the chain harrow.

Honda ATV with 4 foot by 4 foot chain harrow

Micro-Tech was incorrectly applied at 2.5 pts/A instead of the recommended rate of 2.5 qts/A.

Treatment 9 (Prowl) was applied on April 28, 1999 after the sweet corn was planted April 19, 1999 and irrigated April 23, 1999, but prior to emergence without any mechanical incorporation. The weather conditions at start of application were: air temperature 61 F, relative humidity 42%, wind 0-4 mph, with cloudy skies.

The plots were observed in late May and early June for crop response (e.g. stunting, yellowing, etc.) to the herbicides applied.

The plots were evaluated for weed control and stand counts of sweet corn on July 2, 1999 (Table II). Plots were partially hoed on June 30, 1999, however the hoed weeds were still present and identifiable and were included in the evaluation.

Sweet corn stand counts and weed counts were made in the center row of the band and broadcast treatments in each replication and the averages are reported in Table II. The counts were taken in 50 feet of the center row and the 50 feet was selected in each replication by starting approximately 75 feet from the front of each replication. Sweet corn stand counts from the 50 feet of row were converted to plants per acre. The weed counts were converted to percent control based on the weed populations in the untreated control.

2000 Duane Homewood: A CO2 plot sprayer mounted on a Honda ATV was utilized to apply both the band and broadcast herbicide applications. The broadcast applications were achieved by utilizing a 5 nozzle spray boom (18 inch spacing) which delivered 10.95 gpa utilizing XR 8002 TeeJet spray tips, traveling at 4 mph, with 28 psi of pressure at the CO2 tank. The band applications were achieved by utilizing a 3 drop nozzle boom (30 inches apart applying a 15 inch band) which delivered 15.46 gpa utilizing TeeJet 8002E spray tips, traveling 4 mph, with 28 psi of pressure at the CO2 tank.

Honda ATV with CO2 Plot Spayer

Each plot is 6 rows wide (3 rows band and 3 rows broadcast) by 300 feet long, replicated 3 times. The herbicides and rate/A used are listed in Table IV.

All treatments were applied May 12, 2000. The broadcast applications were applied first starting at 7:25 a.m. and weather conditions at the start of the herbicide applications were: wind 0 mph, air temperature 38 F, soil temperature 48 F, relative humidity 38%, and clear skies. All treatments of broadcast and band applications (except Prowl) were completed by 11:00 a.m. Those treatments were shallowly incorporated utilizing a 4 by 4 foot chain harrow pulled behind a Honda ATV.

Duane Homewood Farm, Montrose, Colorado - 2000

The corn was planted by the cooperator using a John Deere planter (Maxi-merge II). The band and broadcast applications of Prowl were made and completed by 2:45 p.m. The weather conditions at completion were: wind 2-6 mph, air temperature 56 F, soil temperature 65 F, relative humidity 20% and clear skies.

The plots were evaluated for crop response (e.g. stunting, yellowing, etc.), weed control, and stand counts of sweet corn on June 16, 2000. The plots were harvested for yields on August 10, 2000. All evaluations were made in the center row of the band and broadcast treatments in each replication and the averages are reported in Table V and VI. The evaluations were taken in 50 feet of the center row and the 50 feet was selected in each replication by starting 125 feet from the front of each replication.

Untreated Control 2000

Sweet corn stand counts and weed counts by species present from the 50 feet of row were converted to plants per acre. The yields from the 50 feet of row were converted to boxes per acre (48 count).

Results and Discussion

1999 John Case: The sweet corn plant populations have been statistically analyzed and there is no statistical difference for herbicide treated plots when compared to the untreated check (Table II). The corn was slow emerging due to cold soil temperatures and soil crusting from rainfall that occurred within days after planting. A rotary hoe was finally used to break the soil crust to obtain emergence.

John Case Farm, Olathe, Colorado 1999

A visual observation of the sweet corn plants in late May and early June, showed that most of the herbicide treatments caused the sweet corn plants to be slightly stunted compared to the untreated control. Prowl and Micro-Tech were the only exceptions and showed equal plant height when compared to the untreated control. The Eradicane treatment showed the most severe stunting in late May and early June.

Barnyardgrass was the major weed species present (approximately 5000 plants per acre) in the untreated controls with adequate pigweed and lambsquarter to obtain an evaluation on these three species. I would consider the pigweed and lambsquarter populations in the untreated control to be considered light weed pressure (approximately 2000 plants per acre).

All herbicide treatments whether applied band or broadcast provided acceptable barnyardgrass, pigweed and lambsquarter control except Prowl and the lower than recommended rate of Micro-Tech.

There were occasional toothed spurge and kochia plants found in the test area but not any were found in the untreated control so no evaluation could be made for these two species.

New seedlings of spurge and barnyardgrass were present in all irrigated furrows whether it was band or broadcast applied treatments.

Sweet corn yields, plant populations, and ear weights are reported in Table III. Plant populations and sweet corn yields were not significantly different due to the herbicide treatments when applied in either the 15 inch band or applied broadcast. However, when plant populations and sweet corn yields were compared between band and broadcast applications, the band applied herbicides had a significantly higher plant population and significantly higher yield (boxes/A).

2000 Duane Homewood: Weed populations of pigweed, lambsquarter, nightshade, and purslane are reported in Table V. There were no significant differences among treatments or application methods (band vs broadcast) primarily due to large variations in weed populations between replications.

Duane Homewood Farm, Montrose, Colorado - 2000

Weed control would not be considered acceptable with any treatment. The variations in weed populations and lack of weed control in this test are due to lack of adequate incorporation of the chemicals. Incorporating with a chain harrow without some rainfall after the light mechanical incorporation is not reliable enough to provide adequate or uniform weed control throughout the treated areas.

Sweet corn phytotoxicity was evaluated on June 16, 2000 as a visual evaluation. There was no visual stunting of the sweet corn plants by any treatment except Frontier at the 24 oz/A rate and Dual II Magnum at the 1.33 pts/A rate. Frontier treated sweet corn resulted in an average of 30% of the plants being stunted compared to the untreated control. Dual II Magnum at the high rate resulted in an average of 20% of the sweet corn plants being stunted compared to the untreated control.

Plant populations and yield per acre are reported in Table VI. There were no significant differences among treatments or application methods.

Although there were no significant differences due to reasons stated above, the trend for weed control was somewhat similar to the 1999 test.

Summary and Conclusion

Based on the two years of testing, we can conclude that sweet corn yields are comparable whether the herbicides tested were applied on a 15 inch band or broadcast applied.

Weed control was comparable with all herbicides tested in both 1999 and 2000 with the exception of Prowl. Prowl did not provide the season long weed control compared to the other herbicides tested in 1999. In addition, Prowl generally had the highest weed population of the species present, when compared to the other treatments in the 2000 test. The herbicides tested in 2000 resulted in variable and unacceptable weed control due to the light mechanical incorporation (one trip with chain harrow) and lack of rainfall following application.

However, there was no initial stunting of the sweet corn plants with the Prowl treatment in the 1999 or 2000 test when compared to the untreated control. All other treatments (except lower than labeled rate of Micro-Tech) applied in the1999 test showed some degree of early stunting when compared to the untreated control. Early stunting was also observed for the high rates of Frontier and Dual II Magnum in the 2000 test when compared to the untreated control.

The concern that must be considered is the consistency of the weed control when using a mechanical method of incorporation that is either light and/or shallowly incorporated (e.g. one trip with chain harrow or tines).

Weed control consistency was much better in the 1999 test due to receiving rainfall following a light mechanical incorporation of the herbicides with the chain harrow. The 2000 test resulted in variable and unacceptable weed control due to no rainfall following light mechanical incorporation.

Therefore, to apply a band or a broadcast application of the herbicides tested with light or shallow mechanical incorporation without at least some rainfall following within a week or so after application, could result in unacceptable weed control.

Table 1: Herbicide Treatments for 1999 Sweet Corn Test

Table 2: 1999 Sweet Corn Herbicide Test · John Case Farm, Olathe, Colorado

Table 3: 1999 Sweet Corn Herbicide Test · John Case Farm, Olathe, Colorado

1999 Plot Plan · Herbicide on Sweet Corn

B=3 Rows Band applied herbicide (15" band) ----------> North BC=3 Rows broadcast applied herbicide Plots - 6 rows x 190 feet long - replicated 3 times See treatment list for herbicide & Rate/A Location - Del Mesa, Farm, East Road, West of 4 Mile Corners, John Case Cooperator

Table 4: Herbicide Treatments for 2000 Sweet Corn Test

Table 5: 2000 Sweet Corn HerbicideTest · Duane Homewood Farm, Montrose, Colorado

Table 6: 2000 Sweet Corn HerbicideTest · Duane Homewood Farm, Montrose, Colorado

2000 Plot Plan · Herbicide on Sweet Corn

2000 Sweet Corn Herbicide Test Duane Homewood - Cooperator 6 rows per treatment (3 rows band and 3 rows broadcast) 3 reps, each rep 300 feet long Location: North of Jasmine Road See treatment list for herbicide and Rate/A

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Colorado State University, U.S. Department of Agriculture and Delta, Mesa, Montrose & Ouray Counties cooperating. Extension programs are available to all without discrimination. No endorsement of products is intended nor is criticism of products mentioned.