Conducting Harvest-Aid Research in Corn E.P. Prostko and A.S. Culpepper Dept. Crop & Soil Science University of Georgia WSSA 2004

Field Corn Production in Georgia u 340,000 A planted (03’) u 55% irrigated u 45% dryland u Avg yields * 118 Bu/A - grain * 118 Bu/A - grain * 16 tons/A - silage * 16 tons/A - silage Source: GASS

Top 10 Most Troublesome Weeds in Georgia Corn Ø TX panicum Ù sicklepod Ú morningglories Û pigweeds Ü nutsedges Ý cocklebur Þ FL beggarweed ß crabgrass à johnsongrass á PA smartweed Webster and MacDonald, 1999

Why are late-season weeds a problem in the SE? u early harvest (Jul-Aug) u warm temperatures u ample rainfall u high humidity u wider rows (36”) u limited herbicide inputs u reduced atrazine residual u delayed applications earlier in season

Objective u to develop a method for conducting small plot harvest-aid research

Research Problems and Concerns? u no previous experience u plot size/layout u design/treatment # u How do we spray? u water volume u weed species u harvest-ability ratings

Plot Size/Layout/Design u RCB 4 reps u 6 treatments u 4 rows X 25’ u 10’ alleys u driveways u Sweet Corn Hybrid * ACX-9454 * ACX-9454 *Why? It was short! *Why? It was short! u Planted April 14

Weed Species u planted annual morningglory u Dual II 1 pt/A - PRE u 2.4 pts/A - 9 DAP u cocklebur, sicklepod, starbur problems u should have sprayed with Basagran or done some hand-weeding

Application Techniques u July 14 (3 months after planting) u JD 6500 High-Boy Sprayer u 4 row boom (18”) u XR nozzles u 5 GPA u 4.5 MPH u flushed boom with clean water and CO 2 after each treatment

4 row boom attached to High-Boy sprayer

CO 2 tank, spray cans, on-off valve

Weed Size At Application - 90 DAP

Harvest-Ability Ratings u subjective rating u ease of mechanical harvest u 1-5 scale u 1 = no problem u 5 = severe problem

Results

Corn Harvest-Ability Ratings - 14 DAT 1-5 Scale a a bc b c

Untreated

Aim 1.0 ozs/A + 1% v/v

Aim 1.6 ozs/A + 1% v/v

1.5 pts/A

Roundup 22 ozs/A

Harvade 8 ozs/A % v/v

Tips for Future Research u limit number of treatments (< 10) u need to add sodium chlorate u control undesirable weeds u identify a short field corn hybrid (mechanical harvest) u longer alleyways (15’) u get better at rating for defoliation/desiccation u conscious of drift u possible funding???

University of Georgia Extension Weed Science (gaweed.com)