Impact of biological seed treatments on maize (Zea mays L.) and soil: I. Crop growth and yield

ABSTRACT

Seed treatments have been used since the 17^th century, but interest has accelerated in the last 20 years due to our increased understanding and importance of the plant microbiome. Particularly, biological seed treatments (BST) have rapidly gained in popularity because soil biota are critical to plant health. Despite growing interest and an expanding market, we still lack understanding of what conditions BST are most effective for plant health. The objective of this study is to understand if seed treatments (including BST) will increase maize (Zea mays L.) growth and grain yield. Here we test 1) maize hybrids and 2) five seed treatments [untreated control (UTC), base fungicide (BFC), BFC + Poncho (P5) (Clothianidin), BFC + Poncho Votivo (P5V) (Bacillus firmus I‐1582), BFC + Poncho Votivo + TWO.O (P5V2) (Bacillus firmus I‐1582 plus Bacillus thuringiensis EX297512)] across four site‐years. Both base fungicide control and BST had little effect on NDVI, plant height, and lodging. We did find a variable effect of BST on maize yield, with a significant site‐year × hybrid interaction (p = 0.06). For instance, in 2019 in northwest Iowa, both BST treatments (P5V and P5V2) increased yield by 1.5 Mg ha⁻¹ compared to the control by an average of (+12%, p < 0.032). BST can improve maize yields, but complex hybrid‐BST interactions warrant further understanding in order to maximize the benefit of BST.

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