38 Ate Today? Thank a Farmer. Better Farming | October 2024 crops: yield matter$ BORON MOBILITY IN PLANTS Reach out to your trusted Certified Crop Advisor & make plans for field trials. By Dale Cowan Back in 2008 we noticed most plant tissue results on corn were indicating low or deficient Boron levels. Boron (B), an essential micronutrient, is required in reproduction processes such as pollen viability and cell wall integrity. Little was known at the time what the yield response would be on corn. We implemented a series of field trials to determine what the yield impact might be. The determination of B status in fields has been traditionally a soil test, sometimes combined with a plant tissue test taken just prior to R1 growth stage (silking) and pollen shedding. We did a lot of B soil testing, which is a hot water extraction methodology. Usually, a soil test level >2 ppm is sufficient and anything below indicates a need for B supplementation. We could not satisfactorily predict responsive from non-responsive soils with a soil test. We reduced the expenditure on soil testing for B and relied more on tissue testing by collecting the ear leaf on corn. Over time, the values told a story of marginal B supply, especially on lighter textured soil types. We implemented a series of field trials and placed 0.5 pounds of B with side-dressed 28 per cent nitrogen. We know that B is very xylem-mobile in plants but not very phloem-mobile. This was the main reason for soil application rather than as foliar – as foliar application will not readily move from the leaf to where it was needed after leaf absorption. Boron uptake in corn is fairly linear from crop emergence to black layer. It seems that a steady uptake is required to accumulate sufficient B to satisfy plant requirements. Our long-term trials are indicating a five-bushel response to 0.5 lbs. of B at side-dress timing. (I have shared this information before in this magazine.) What is different now is we did an initial project on how we might take plant tissue samples differently. I listened to Dr. Tony Vyn at an ag conference last winter question what leaf position on the corn plant was best for nitrogen and sulphur status. Was the traditional ear leaf (EL) best, or the one below that (EL-1), or the one below that one (EL-2)? For sulphur, the very top leaf or flag leaf (FL) was proposed to be the best for sulphur status. At the time of writing this article I have no yield data to know that. Dale Cowan photo Korina Velema, summer intern with AGRIS Co-operative, collects leaf tissue samples on corn. GUARDIANNETWORK.CA REGISTER FOR A GUARDIAN NETWORK SUICIDE PREVENTION TRAINING TODAY
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