Do Crop Rotation and Tillage Influence Soybean Seed-Applied Inoculant Decisions?
2016
Marburger, David A. | Mourtzinis, Spyridon | Gaska, John M. | Conley, Shawn P.
Seed-applied inoculants containing Bradyrhizobium japonicum are commonly used in soybean [Glycine max (L.) Merr.] to promote biological N fixation, but the interactive effects of crop rotation or tillage system by inoculant use have not been well examined. Field research trials were conducted in a long-term crop rotation experiment during 2009–2011 to measure soybean yield and grain composition response to seed-applied inoculants as influenced by crop rotation and tillage system. Main plots were two tillage treatments (no-till and conventional). Subplots consisted of seven crop rotation sequences involving corn (Zea mays L.) and soybean. Sub-subplots consisted of three rhizobia treatments: Optimize, Excalibre, and a control. The results showed that crop rotation and tillage practice did not interact (P > 0.05) with inoculant use to affect seed yield but inoculant treatment response was dependent on the crop rotation sequence when this interaction was sliced. Inoculant use increased yield by 8 and 10% and 7 and 9% within the third year soybean after 5 yr of corn and fourth year soybean after 5 yr of corn rotations, respectively. Seed treated with Optimize yielded 130 kg ha⁻¹ (4%) more than the control. Crop rotation and tillage practice also did not interact (P > 0.05) with inoculant use to influence grain composition (i.e., protein and oil content and yield). The data from this study, alongside previously published research results, suggest that growers need to consider product cost and efficacy, probability of return on investment, and other individual risk factors when making inoculant use decisions.
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