21 Story Idea? Email Paul.Nolan@Farms.com Better Farming | June/July 2024 Fungicide in Soybeans soybean crop is the happiest. Most of a soybean’s life cycle occurs during the vegetative stages. Seventy per cent of the soybean lifecycle occurs when growing plant stems and nodes, followed by about 40 percent of a plant growing branches from nodes. From here, smaller portions of a plant are broken down into seed size development, followed by pollinated flowers and then seeds per pod. Although most of the plant’s life is in vegetative stages, it is the reproductive stages that are most crucial to soybean yield. All nodes produce flowers; however, yield on a soybean plant is more located around the middle and upper canopy. This is driven by absorption of light entering the canopy. Less than 25 per cent of light makes it down to the bottom quarter of a soybean plant. Hence the differences in where yield is found on a plant. Soybeans abort higher percentages of flowers in the lower canopy due to differences in light absorption and sugar movement within the plant. Studies have shown that 20 to 80 per cent of flowers produced will be aborted at the R2 stage. With newer plant breeding, soybeans have changed over time. Plant leaves are smaller and changed in architecture, allowing more sunlight to pass through the middle-lower portions of the plant, reaching lower nodes. Again, the middle to upper portion of a plant are the higher-yielding parts. Hence the reason to make sure this part of the plant is kept healthy from insects, diseases, and other stresses. Here in Eastern Ontario, keeping soybeans happy means applying fungicides in a timely manner to reduce white mould infection. In our 2023 white mould fungicide trials, we focused on one application of Viatude fungicide at the R 1.5 to 2.5 stage. Yield results showed a 3.2-bushel advantage to the fungicide applied versus no fungicide gained by yield protection. The 2023 season was a white mould magnet year. In a few trials, we had Fungicide plant health edit from DroneDeploy. Droen Deploy Plant Health photo Soybeans growing in previous corn ground at the V2 stage of development. Paul Hermans photo
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