Tonight I did some foliar manganese applications on the pumpkin plants. Colorado soils tend to be naturally low in Manganese. Not only that but our high ph soils make manganese deficiencies more common, especially when the soil iron is high as it often is in the Denver area. High potassium soils, like my patch have, can make the problem worse.
Manganese plays a significant role in photosynthesis. The formation of free oxygen radicals during water splitting and ultimately the release of oxygen is not possible under Mn-free environments. Mn is the only element that can contribute the necessary electrons for this biochemical process.
I recently read that manganese sulphate added to the soil, like what I've been using the last few years, has no effect on the plant. I watched the Ron Wallace DVD again this last weekend and he was talking about the manganese issues he was having in 2012 and he showed a picture of the exact same bag of manganese that I've been using. Ron does regular tissue tests on his plant and he was never able to get his manganese to move up in the tissue tests. The reason for that, as I said before, is because soil applications of manganese sulphate don't work. Soil applications apparently don't work in the form we have been doing it and Ron's soil test seemed to prove that.
I have read that a foliar application is the best way to fix the problem and that a chelate is the best form to use. I looked high and low for any kind of a foliar manganese and couldn't find anything that didn't require a purchase that would only be appropriate for a large farm. As such I decided to take a bit of a risk and I bought a pill form that is meant to be used as a human supplement. I first tried it on one plant and then waited a few days before trying it on other plants.
The brand I am using is Solray 50mg capsules. I simply pour the capsule into my sprayer and then spray the bottom of the pumpkin leaves. I don't use all of the manganese water. Just enough to cover the bottom of my leaves and the rest is discarded. Not sure if this will work or not. Doesn't seem to hurt and I haven't figured out a better way to do it yet.
The 1421 plant is about 6 inches from the end of the hoop house. I'm hoping to keep it in the hoop house for 4-5 days if I can. I still need to get the hail netting up and there is a forecast for a windy day ahead and I don't want to make the mistake that I made last year of removing the hoop house only to have 20 mph winds the next day.