Phosphite (phosphorous acid): Fungicide, fertilizer or bio-stimulator?
Version of Record online: 25 MAR 2009
© 2009 Japanese Society of Soil Science and Plant Nutrition
Soil Science & Plant Nutrition
Volume 55, Issue 2, pages 228–234, April 2009
How to Cite
THAO, H. T. B. and YAMAKAWA, T. (2009), Phosphite (phosphorous acid): Fungicide, fertilizer or bio-stimulator?. Soil Science & Plant Nutrition, 55: 228–234. doi: 10.1111/j.1747-0765.2009.00365.x
- Issue online: 25 MAR 2009
- Version of Record online: 25 MAR 2009
- Received 3 September 2008.; Accepted for publication 25 December 2008.
Phosphite (; Phi), a reduced form of phosphate (; Pi), is widely marketed as either a fungicide or fertilizer or sometimes as a biostimulant. This is confusing for both distributors and growers. The present paper explores data from various studies to clarify that Phi does not provide plant P nutrition and thus cannot complement or substitute Pi at any rate. In addition, Phi itself does not have any beneficial effect on the growth of healthy plants, regardless of whether it is applied alone or in combination with Pi at different ratios or different rates. The effect of Phi on plants is not consistent, but is strongly dependent on the Pi status of the plants. In most cases, the deleterious effect of Phi is evident in Pi-starved, but not Pi-sufficient, plants. Plants fertilized with Pi allowing for approximately 80–90% of its maximum growth might still be at risk of the effect. This negative effect becomes more pronounced under more seriously Pi-deficient conditions. Although a number of studies have shown positive crop responses to Phi, these responses are likely to be attributable to the suppression of plant diseases by Phi and/or to Pi formed from oxidation of Phi by microbes. In addition, indirectly providing P by Phi-to-Pi oxidation is not an effective means of supplying P to plants compared with Pi fertilizer. An understanding of these issues will aid the right selection of fertilizer as well as minimize the harmful effects of Phi use on crops.