Field-Scale Studies Show Significant Location X Seeding Depth Interactions for Corn and Soybean Populations and Yields.

Limited research has been conducted on optimum corn and soybean seeding depths. We conducted field-scale studies in NY to evaluate populations and yield of corn (soybean previous crop) and soybean (corn previous crop) in 2013 (planted in early May and mid-May, respectively) and 2014 (planted in late May and early June, respectively) at 1.0, 1.5, 2.0, and 2.5 inch depths. Silt loam soils predominated at one corn site (chisel), clay loam soils at two sites (moldboard plow or disc), and silty clay loam soil at another site (no-till). Silt loam soils predominated at one soybean site (no-till), and clay loam and gravelly loam soils at the other two sites (chisel).

Corn plant populations and grain yields had strong year x location x seeding depth interactions. Although yield differences among seeding depths were generally small, increasing the depth from 2.0 to 2.5 inches at the silty clay site decreased yield ~6%. In contrast, decreasing the depth from 2.5 to 2.0 inches at the clay loam site decreased yield ~9%. The significant year x location x seeding depth interaction for yield indicates that corn growers in NY should adjust seeding depth to soil conditions, although predicting ensuing soil conditions after planting is difficult.

Seeding depths >1.5 inch decreased soybean plant populations at two sites by ~10%. Yield did not respond to seeding depth in 3 site/years and showed quadratic responses in 3 site/years.  Yield differences, however, were small at responsive sites with ~5 % difference at the no-tilled site, and ~7.0% at the gravelly loam site. The 1.5 inch seeding depth generally resulted in excellent early stand establishment (>85% emergence for all site/years except for 77% at the gravelly loam site in 2013) and maximum yield in two of the three site/years where yields responded to seeing depth.