OPTIMIZING SEEDING RATE FOR LATE-SEEDED WINTER-WHEAT IN THE MIDDLE ATLANTIC REGION

In the Middle Atlantic Region, fall rain sometimes delays planting soft red winter wheat (Triticum aestivum L.). This study measured whether the yield loss due to a planting delay can be reduced by an increased seeding rate. Field experiments were carried out in the 1989-1990 and 1990-1991 crop years at Beltsville and Clarksville, MD. Cultivars 'Florida 302' and 'Twain' were planted on three dates, recommended seeding date (Date 1), 2 to 3 wk later (Date 2), and 4 to 6 wk later (Date 3) at seeding rates of 38.0 (Rate 1, currently recommended), 47.5 (Rate 2), 57.0 (Rate 3), and 66.5 seeds sq ft (Rate 4). Delayed seeding had more detrimental effects on FL302 than on Twain. The effects of date, rate, and their interactions on yield were not significant at Beltsville. At Clarksville, wheat planted on 4 to 6 wk after the fly-free dates had significantly lower yield than wheat planted earlier. Regression analyses showed that the yield losses from the last planting was reduced 40% by increasing seeding rate from 38 to 57 seeds/sq ft. Delayed seeding reduced spikes and plants per unit area while a higher seeding rate increased them. Thus increased seeding rates counteracted the negative effect of a seeding delay on yield.