Maize yield response to mid-season stalk breakage

In 2022, over 198.8 million ha was insured across the United States, with indemnity payments exceeding $18.2 billion. In the US Midwest, strong wind gusts associated with thunderstorms often cause significant stalk breakage in maize (Zea mays L.) fields. This study investigated whether crop insurance adjustment tables continue to be accurate when adjusting for maize yield after stalk breakage has occurred. Two experiments were conducted to assess the effect of below-ear and above-ear stalk breakage at four levels of severity (0%, 25%, 50%, and 75%) and at three timings (V13, V17, and tassel stage [VT]). Trials spanned nine site-years across Iowa, Minnesota, and Nebraska from 2019 to 2022. Below-ear breakage results in a loss of the primary ear, while above-ear breakage reduces the size and weight of the harvestable ear. Plant density, primary and secondary ear counts, grain yield, and kernel mass were measured. The number of secondary ears was highly influenced by the damage type. When breakage occurred above the ear node, 25% damage severity resulted in a 35% increase in the number of secondary ears compared to the untreated control. When breakage occurred below the ear node, the impact was much more evident, with an 85% increase of secondary ears. On average, breakage above the ear resulted in a 9.5%, 18.6%, and 25.2% yield penalty for 25%, 50%, and 75% severity, respectively. As expected, for the same damage severity, below-ear breakage resulted in much higher yield penalties (13.3%, 32.6%, and 55.0%). There was no clear relationship between damage severity and kernel weight.