In various regions of eastern Kansas, an increasing number of producers are utilizing planters with row units on 15-inch spacings to plant wheat as an alternative to using drills with 7- to 10-inch spacings. Potential perceived benefits for using planters to sow wheat are: equipment savings, better seed placement, better plant emergence, and a perception that planters can manage the residue more effectively than a drill in no-till conditions.
Research evaluating the effect of sowing wheat with 15-inch planters in no-till conditions was evaluated to improve the management practices with this relatively new method of planting wheat in Kansas. The Kansas Wheat Commission funded this research for the 2011-12 season.
Wheat plots were sown on Oct. 21, 2010 and Oct. 12, 2011 at the East Central Experiment Field near Ottawa. We sowed wheat in 7-inch row spacings with a Great Plains Solid Stand No-Till Drill and 15-inch row spacing with a Kinze 3000 planter. Other variables included seeding rate (1 and 1.5 million seeds per acre) and herbicide treatment (none vs. a residual sulfonylurea herbicide). All plots received 95 lbs nitrogen (N) per acre in 2011, and 125 lbs N per acre in 2012.
Effect on Weed Densities
In 2011, weed emergence of henbit, Carolina foxtail, and smallflowered bittercress was greater in the 15-inch rows than the 7-inch rows. The increase in emergence in the 15-inch wheat rows is likely because of less shading by the wheat. Seeding rate didn’t affect weed emergence in the drilled wheat. In the 15-inch row plots, more henbit emerged at the seeding rate of 1 million than at 1.5 million. Smallflowered bittercress emergence was greater at the higher seeding rate, however. The
row spacing and seeding rate that suppressed the greatest number of weeds from emerging was the 7-inch row spacing at the low seeding rate.
A similar general pattern was seen in 2012, with greater weed emergence with wheat in wider rows. Henbit emergence was about 3.5 times higher in wider rows vs. narrower rows. Common chickweed emergence was also significantly inhibited by wheat shading in the narrow 7-inch vs. 15-inch rows. Seeding rates had no effect.
Effect on Yields
Seeding rate had no effect on wheat yield in either 2011 or 2012. Row spacing did have an effect. In 2011, wheat in narrow 7-inch rows yielded 14.2 bu/acre more than in wide 15-inch rows, averaged over seeding rates and herbicide treatments. In 2012, wheat in 7-inch rows had a yield advantage of 18.2 bushels per acre over 15-inch rows.