Phosphate

I suppose the next important nutrient would be phosphate. This will probably surprise some people because they were expecting nitrogen. I explained in my last post on calcium why I think that nitrogen is pushed so heavily by the so called authorities on the subject. Yes nitrogen is very important, but it’s not the end of all things like the fertilizer companies would like you to believe.

Phosphate is the major catalyst in living systems, it is necessary for photosynthesis and metabolism which also means it is a key in high refractometer readings. The key to phosphate availability is soil microorganism activity, which is really the bottom line for almost everything. Again, as with calcium, there can be loads of phosphate but if that phosphate is not available to the plant you can just as well consider that it is not there, that is, until you do something to make that phosphate available.

If there is a phosphate deficiency (functional) then calcium is tied up, so it is important to work with both calcium and phosphate at the same time or you could be beating yourself over the head with a stick and getting nowhere. Interestingly enough, if things are not in balance tricalcium phosphate is formed in high calcium soils, which ties up the phosphate. Tricalcium phosphate is just what it sounds like, three calcium and one phosphate in the molecule. What you can do in a pinch is knock off the extra calcium from the tri molecule with an acid, what is even better is to use biology to do it for you, though that is a slower method.

Iron also ties up phosphate and again, the best way to prevent and cure this is through the soil biology. You will find that I go back to soil life an awful lot but I’ll just keep hammering it in since it really is the most important thing to be aware of in my opinion.

If you need to apply phosphate there are several types that you can get, I’ll class them as natural and manufactured. The manufactured are usually the acid phosphates, and the numbers look really amazing on these, until you realize that acid based fertilizers are only 10-20 % efficient so an acid based 10-10-10 fertilizer is really only a 1-1-1 functional analysis! It’s a numbers game that the fertilizer companies (and consequently, the universities, who are well paid by the fertilizer companies) don’t want you to know about. The natural forms of phosphate are much better, which more than makes sense when we know that the key to phosphate availability is soil microorganisms and whatever we do to kill them off (acid fertilizers) will consequently cause the phosphate to be even more tied up.

Phosphate is not consumed as someone selling it to you would like you to believe, it is simply recycled through the system. It’s really an energy effect taken from when the phosphate is converted from phosphate to diphosphate to triphosphate and back to diphosphate, and phosphate again, each conversion liberates energy which is then used. It’s a matter of knocking off and recombining the molecule, and this is really important because phosphate is the primary energy transport system in the soil. Since it’s also a major actor in photosynthesis (sunlight, CO2, H2O, P2O5= sugar) you see that it cannot be ignored. Of course, like everything, you can have too much phosphate and that will create plenty of problems too, things like major broadleaf weed patches where you thought you had planted your wheat or corn. I remember one pinto bean field I harvested a few years ago for an organic farmer. He had not entirely paid attention and had applied a lot of soft rock phosphate to a 100 acre field, half of which had been a feedlot years ago. The previous year he had grown oats and before that buckwheat, both of which are major phosphate scavengers. The combination of feedlot (manure is extremely high in phosphate) double crop of the phosphate scavenging plants and the application of soft rock phosphate made for an interesting looking field come harvest time. The entire field had a tremendous load of pigweed but there was a line right where the old fence had been (I wondered why there was a line and he told me about the feedlot) on the pasture side there was a lot of pigweed, on the feedlot side there was almost nothing but pigweed. Forget trying to get the bean cutter through that mess, we ended up swathing it and loosing a lot of beans.

Lesson learned, you can have too much phosphate! Weeds of the pigweed family almost always point to high phosphate (amaranth, redroot pigweed, lambs quarters etc)

Plants deposit organic acids into the soil through root exudates which the microorganisms consume and the waste is plant food, to use technical terms. Some plants have root exudates that also act on certain nutrients, oats and buckwheat are two that particularly work on phosphate. One of the quick ways to make the phosphate available in a field is to grow a cover crop of either oats or buckwheat, tilling it into the soil. Not only have the roots released some of the tied up phosphate in the soil, but the plants themselves have taken up quite a bit of the phosphate and when you till them in and after the microorganisms have decomposed them this phosphate is readily available to the following crop.

Sometimes there will be a true deficiency of phosphate so we will need to bring some in, my favorite source is manure but not everyone can get enough of that so some other sources are;

Soft rock phosphate, the North Carolina black is also 40 % calcium so this would be a good source of both and it comes with almost 5% carbon so it holds the calcium in place.

Hard rock phosphate.

Phosphoric acid (soaps, soda pop, harsh cleaners) Not the best source but can be used as a foliar if you have to.

Bone meal is 6% P2O5.

Liquid fish is 2% P2O5.

And as always, if you have a properly functioning micro life in the soil you most likely will not have a problem with phosphate so get to work on those microorganisms!