MisterBlah
Well-Known Member
I'm sure all of you have heard of phosphates before. It's how phosphorus is delivered to your plants. But many of you may not have heard of phosphites.
Phosphate fertilizers are generally made from phosphoric acid (H3PO4) and in solution, the ion PO4-, is the phosphate ion. Phosphites are made from phosphorous (not phosphorus) acid (H3PO3) and in solution, the ion PO3-, is the phosphite ion. Know the difference from a chemical standpoint. And now, also, learn the differences.
There is still quite a bit of confusion regarding these source products.
All Phosphates are fertilizers. Monopotassium Phosphate, Dipotassium Phosphate, Monoammonium Phopshate, Diammonium Phosphate, Phosphoric acid, etc.
Now, what are Phosphites? Are they fertilizers, fungicides, bio-stimulants, or an inducer of Systemic Acquired Resistance (SAR) in plants. On the topic of SAR: In other words in the presence of phosphites, certain genes are “turned on or off” that help the plant in the presence of certain diseases.
What I mean by all that is that even many scientists aren't quite sure where to categorize phosphites.
So, let's learn what phosphites actually do and why they are useful.
Is it a fertilizer? No, not really. Most contend that there is no evidence to date that can clearly demonstrate that plants use PO3 directly as a P nutrient. If you feed only phosphites, you will see symptoms of a phosphorus deficiency in the plant even though the plant feeds on them identically to phosphates.
Is it a fungicide? There is plenty of evidence of the positive effect against pathogens that belong to the Oomycota phylum, the pathogen that causes Downy mildew (Bremia lactucae) and the pathogens that cause root, crown rot in avocados and brown, foot rot (Phytophthora spp.). As an aside, oomycytes aren't actually fungi, but for practical purposes are grouped in with fungi. But this doesn't exactly answer the question. Now for phosphites to be considered a fungicide, it has to kill the pathogens. There isn't exactly a lot of evidence that shows it specifically killing, rather it causes these pathogens to slowly die out or practically ignore their deleterious effects.
Is it an inducer of Systemic Acquired Resistance (SAR) in plants? This is where I most tend to think it falls under. Basically, it causes the plant to survive and even thrive in the presence of the disease. I'm sure you have all heard of the benefits of silica for doing the same thing. Phosphites, when used in low concentrations like silica (<30ppm), can have many benefits for improving SAR.
For more reading: http://edis.ifas.ufl.edu/hs254
Phosphate fertilizers are generally made from phosphoric acid (H3PO4) and in solution, the ion PO4-, is the phosphate ion. Phosphites are made from phosphorous (not phosphorus) acid (H3PO3) and in solution, the ion PO3-, is the phosphite ion. Know the difference from a chemical standpoint. And now, also, learn the differences.
There is still quite a bit of confusion regarding these source products.
All Phosphates are fertilizers. Monopotassium Phosphate, Dipotassium Phosphate, Monoammonium Phopshate, Diammonium Phosphate, Phosphoric acid, etc.
Now, what are Phosphites? Are they fertilizers, fungicides, bio-stimulants, or an inducer of Systemic Acquired Resistance (SAR) in plants. On the topic of SAR: In other words in the presence of phosphites, certain genes are “turned on or off” that help the plant in the presence of certain diseases.
What I mean by all that is that even many scientists aren't quite sure where to categorize phosphites.
So, let's learn what phosphites actually do and why they are useful.
Is it a fertilizer? No, not really. Most contend that there is no evidence to date that can clearly demonstrate that plants use PO3 directly as a P nutrient. If you feed only phosphites, you will see symptoms of a phosphorus deficiency in the plant even though the plant feeds on them identically to phosphates.
Is it a fungicide? There is plenty of evidence of the positive effect against pathogens that belong to the Oomycota phylum, the pathogen that causes Downy mildew (Bremia lactucae) and the pathogens that cause root, crown rot in avocados and brown, foot rot (Phytophthora spp.). As an aside, oomycytes aren't actually fungi, but for practical purposes are grouped in with fungi. But this doesn't exactly answer the question. Now for phosphites to be considered a fungicide, it has to kill the pathogens. There isn't exactly a lot of evidence that shows it specifically killing, rather it causes these pathogens to slowly die out or practically ignore their deleterious effects.
Is it an inducer of Systemic Acquired Resistance (SAR) in plants? This is where I most tend to think it falls under. Basically, it causes the plant to survive and even thrive in the presence of the disease. I'm sure you have all heard of the benefits of silica for doing the same thing. Phosphites, when used in low concentrations like silica (<30ppm), can have many benefits for improving SAR.
For more reading: http://edis.ifas.ufl.edu/hs254