Bill Cox, John Orlowski, and Phil Atkins, Department of Crop & Soil Sciences, Cornell University
Soybean acreage continues to expand in New York with many first-time growers now planting the crop. Many new growers plant soybeans with a corn planter instead of a grain drill, which has been the almost exclusive planter for soybeans in NY over the last 30 years. Also, some experienced soybean growers, who no longer plant wheat, have switched to a corn planter to save on equipment costs. In addition, some growers are purchasing new row crop planters with inter-units allowing for corn planting in 30-inch rows and soybean planting in 15-inch rows. With that in mind, we conducted field-scale row spacing by seeding rate studies in 2010 and 2011 on farms in Cayuga and Livingston Counties to evaluate soybeans planted with a drill in 7.5 inch rows vs. planting with a row crop planter in 30-inch or 15-inch rows. The Cayuga County farm was a no-till site and the Livingston County farm was a chisel tillage site. The growers performed all management practices and we took numerous measurements, of which early stand counts and yield (with a Weigh Wagon) will be presented here.
Early stand establishment at Cayuga Co. averaged about 72% (107,287 plants/150,000 average seeding rate) for the drilled soybeans in 7.5 inch rows (Table 1). In contrast, early stand establishment averaged about 83% in 30-inch rows at Cayuga Co. Likewise, drilled soybean in 7.5 inch rows had much lower stand establishment at the Livingston Co. site. Drilled soybeans in 7.5 inch rows averaged 69% early stand establishment (103,645/150,000) compared to about 81% in 30 inch rows at the chisel tillage site. Apparently, under actual grower practices, stand establishment is much better in 30-inch rows when planted with a corn planter compared with drilled beans in 7.5 inch rows.
Poorer stand establishment for drilled beans may partially explain the yield data from these field-scale studies. Previous small-plot research at the Aurora Research Farm in the mid-1990s and in the late 2000s indicated that drilled beans yielded anywhere from 7 to 15% greater than 30-inch beans planted with a corn planter. In these field-scale studies, however, row spacing did not affect soybeans at the no-till Aurora site. At the chisel tillage site, drilled beans yielded only about 4% greater than beans in 30-inch rows, if planted at 170,000 seeds/acre (Table 1). Some wheel traffic damage from post-emergence pesticide applications may also have damaged the drilled soybeans more than the 30-inch soybeans, which could have reduced any yield advantage for drilled or narrow row soybean.
Conclusion
Row spacing had much less of an impact on soybean yield than expected in these field-scale studies. At a no-till site, row spacing did not affect yield. At a chisel tillage site, drilled soybean planted at 170,000 seeds/acre yielded about 4% more than 30-inch soybean at 130,000 seeds/acre. Apparently, growers can plant soybeans in 30-inch rows without much of a yield loss, especially in years or fields where yields are in the 50-65 bushel/acre range. At sites or in years where growth is slow and yields are low, the yield advantage for drilled soybeans may be greater than reported in this study.
