Wednesday, November 15, 2006

Impact of Application Timing and Crop Row Spacing on Fungicide Penetration into a Soybean Canopy and Grain Yield.

Shane Hanna, Shawn Conley, and Greg Shaner. Purdue Univ, Dept of Agronomy, 915 W. State St, West Lafayette, IN 47907-2054

The objectives of this experiment were to quantify the impact of crop row spacing and spray application timing on canopy penetration and coverage, and to quantify the impact of fungicide application timing on crop yield and crop injury caused by sprayer wheels. The experimental design was a randomized complete block with three replications. The main factors were crop row spacing (76, 38, and 19 cm) and Quilt fungicide application timing (unsprayed or applications at growth stage R1, R3, R5, R3+R5, or R1+R3+R5). Spray canopy coverage was quantified at 30-cm height increments in the soybean canopy. Plots were 13.7 by 91.4 meters. The experiment was conducted at three locations in Indiana and utilized field-scale application equipment. Crop row spacing did not affect spray canopy coverage at any application timing; however coverage differed at the 30 cm height increments. Grain yield was 7% greater in the 19 and 38 centimeter row spacing than in the 76 centimeter row spacing in the non-wheel track area; however yield was similar among all row spacings in the wheel track area due to wheel track damage to the crop. Fungicide application time affected neither soybean yield nor frogeye leaf spot severity. Averaged across the 19 and 38 cm row spacings grain yield was greater in the non-wheel track than in the wheel track areas at the R3 (7.0%), R5 (7.2%), R3+R5 (9.6%), and the R1+R3+R5 (5.2%) application timings. Wheel track damage and seed input costs are factors to consider when planning for multiple pesticide applications after soybean has reached R1.