Row unit down force and coulter effects vary by environmental conditions in organic no-till soybeans

Concerns over tillage intensity and soil erosion in organic cropping systems have prompted the development of reduced tillage organic systems that use cover crops rather than soil disturbance as the primary weed control tool. However, planting into high residue cover crop mulches may inhibit crop establishment due to poor seed placement. Adaptation of agricultural equipment to high residue planting conditions could reduce variability in crop stands, thereby improving grain yield. Field trials at the University of Wisconsin Arlington Agricultural Research Station, Marshfield Agricultural Research Station, and three on-farm locations representing seven site-years of data from 2019 to 2020 comprised a 2 x 2 x 2 x 2 factorial experiment comparing (1) a low (457,135 seeds ha-1) versus high (555,986 seeds ha-1) soybean [Glycine max (L.) Merr.] seeding rate, (2) a 13 fluted-wavy coulter versus no coulter attachment, (3) low (667 N) versus high (1334 N) row unit down force, and (4) spiked versus rubber closing wheels on soybean stand establishment and grain yield in an organic cover crop-based reduced tillage system. Combined across site-years, high row unit down force and coulters increased soybean stand establishment by 2.3% and 2.4%, respectively; however, the magnitude and direction of effects varied within each site-year. Winter rye (Secale cereale L.) biomass accumulation negatively correlated to soybean stand establishment and demonstrated trends toward increasing soybean yield. Significant correlations between soybean stand establishment and yield were noted under high rye biomass conditions, indicating potential improvements to soybean yields by increasing plant stands. Rye biomass mulch accumulation reduces soybean stand establishment. Row unit down force of 1334 N and a coulter most consistently increased soybean stand establishment. Improvements in soybean plant stands translated to higher grain yields under elevated rye biomass conditions.