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Reapplication of Fertilizer Following an Early Season Rain/Flood

deluxestogie

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Southern States Premium Vegetable Grower 10-10-10 (low chlorine) Fertilizer Solubility

Living less than ~150 yards from the Eastern Continental Divide, "flooding" is always just an annoyance and pain in the butt for me, but never worse than that. The following, though, is about the effect of prolonged, heavy rain on applied fertilizer. Should some be reapplied?

Extension services loosely suggest reapplying about 1/2 the original amount of fertilizer if a rain/flood event occurs prior to transplant, and up to two weeks after transplant. Reapplication less than 4 to 6 weeks prior to harvest will adversely impact the leaf maturation schedule.

I dispersed the appropriate amounts of this fertilizer onto my garden beds on Sunday. Starting Monday evening, a continuous four days of rain was projected to drop a minimum of 3½ inches of rain. [I would end up with much more than 3½".]

The question arose in my mind about whether or not my fertilizer would all be washed away before I even planted anything. I foresaw no moving flood of water carrying away anything, but did expect the beds to be totally soaked, perhaps with standing water, once the rain had stopped.

As a crude answer to my question, I put ½" of my fertilizer into an 8 ounce cup, and set it out on my porch steps. The plan was to wait until any standing water had dissipated from the garden beds, then pour off the rainwater from my 8 ounce cup, to see how much of the tiny, multi-colored rock fertilizer had dissolved away. Had I used a liquid fertilizer preparation, then at least half, if not most of it would be gone following such a heavy rain prior to planting.


Test start (Monday evening).


After 24 hours (Tuesday evening).


After 36 hours (Wednesday mid-day). With the cup threatening to overflow, I nested it inside a larger container. So quantitative measurements are no longer valid.


After 48 hours (Wednesday evening).

What to do when I can't build an ark? Take photos through the farmhouse windows.


Deep river,
My home is over Jordan.
Deep river, Lord,
I want to cross over into campground.



After 60 hours (Thursday morning). Standing water in the upper bed.


After 60 hours (Thursday morning). Water's a-risin'.


NOAA Flood Warning Thursday noon.

The shot below is pretty much the end of the major rain event. The inner cup filled to the top. I then nested it within a carefully calibrated potato salad tub. The tub has filled to about 4 inches. So, using my genuine Berkeley fudgesicle measuring stick, the fudged total is about 8 inches of rain, give or take an inch or so. (It may yet rain a bit more. Some of the collected water may have evaporated by now.)


After 72 hours (Thursday evening-ish).


Test end, water decanted.

Comparison:



CONCLUSION: Just being under stationary water appears to have dissolved 1/4 to 1/3 of the starting fertilizer. Suspended fertilizer particles can be seen (discoloration of the remaining fluid) after decanting the rainwater. Perhaps the fertilizer applied to the bed just distributed itself within the bed, though its having washed away seems more likely. So I should probably replace at least 1/4 of the original amount applied to each bed. The standard recommendation from extension services to reapply 1/2 the original amount of fertilizer following an early season rain/flooding event is certainly within reason.

Although this experiment was not quantitatively precise, it does serve as a useful approximation.

Bob
 
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