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MemberFebruary 9, 2023 at 1:06 pm015589
For our crops (stone fruit) we tend to know the nutrients that are traditionally low, and at what season they are more likely to be low. Applying then is only a guess, but an educated one to make up for the lag time on getting sap results. For us, and I would imagine it would be the same for a leafy green, the main limit is often phytotoxicity, either from a specific nutrient or the net amount of material in the solution. I’d divide the nutrients as macro, micro, and zinc. On a annual crop I’d imagine you do OK with a soil-applied macro. As a foliar I would suggest you seek the best quality chelated form available, and spray at increasing rates until you see a response. A test row, perhaps. Zinc is the one micro we don’t bother to use as a chelate because we can get it in as a mineral spray directly, and is the main nutrient our trees are deficient in. That said, you would likely still need a zinc chelate to keep a low rate/high efficiency spray, since no one wants lettuce that tastes of zinc. We have the luxury of post-harvest applications. I imagine every chelate has a different effectiveness for each crop, based on waxiness for example. Try what you normally use against something else and see which is better. I don’t think it would take more than a couple years with a “head-to-head competition” to see what works best. Testing that control application vs a test row is 2x the money, but will pay for itself if you plan to be growing for the long haul.