Improving Management Practices for High-Yield Soybean Production in Illinois.

A common perception among Illinois soybean growers is that soybean yields have reached a plateau, particularly if growth of soybean yields is compared to that of corn. While it is clear that soybean genetics have improved over time, one possible explanation for slow growth of soybean yields may be related to less focus on management practices. To address this possibility, we experimentally evaluated five categorical management factors (fertility, variety, foliar pest protection, seed treatment, and row spacing) at four locations (two trials per location) across Illinois in 2012. A ‘standard’ management practice (a variety of typical maturity for the region with either untreated seed or a basic seed treatment) was compared to a ‘high tech’ management practice in which a full-season variety for the region was grown with additional N, P, S, and Zn fertility (MicroEssentials SZ), foliar protection from insects and fungal pathogens, and an advanced seed treatment package consisting of a fungicide, insecticide, and nematicide. All treatments were compared in 20-inch and 30-inch rows. Significant yield responses to the high tech package were detected in six of eight trials in 2012. Inappropriate variety placement resulted in no response to intensive management in two trials highlighting the importance of selecting high yielding germplasm as a component of intensive soybean management systems. Averaged across six trials in 2012, the ‘high tech’ package increased yield by 9.9 bu acre^–1 (P ≤ 0.05). Narrow row spacing increased yield at three of the four locations; Champaign, DeKalb, and Rushville with respective yield increases of 3.0, 6.5, and 1.6 bu acre^–1. At the six management responsive sites, banded fertility (N, P, S, and Zn) and full foliar protection (fungicide + insecticide) had the greatest individual effects on yield with respective contributions of 4.3 and 3.6 bu acre^–1 when averaged across the traditional and high tech systems. Switching from a variety of ‘normal’ maturity to a fuller season variety had a 3.2 bu acre^–1 effect on yield, and use of a seed treatment including a fungicide, insecticide, and nematicide contributed an additional 2.6 bu acre^–1. The results of this project highlight the importance of choosing a high yielding, locally-adapted soybean variety and managing it with fertilizer placement and a full suite of crop protection products.