Has anyone noticed that the bagged lawn fertilizer does not have Phosphorus in it now. Or at least it is hard to find it. Most of the fertilizer at the local hardware store is 25-0-5 or something close to that.
Are they cracking down on the overuse of Phosphorus fertilizer on lawns?
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Smallgardener
- Senior Member
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- Joined: Mon Jul 02, 2012 1:18 pm
- Location: SW Kansas
I know that Minnesota has restricted the use of fertilizers containing phosphorus due to phosphate intrusion into groundwater in that state. If the groundwater (such as there may be remaining) in the Oglalla Aquifer is contaminated with phosphates, this restriction may have been imposed on states drawing from that aquifer.
Maybe a check with your local water department/agency could shed some light on the situation?
Cynthia H.
Sunset Zone 17, USDA Zone 9
Maybe a check with your local water department/agency could shed some light on the situation?
Cynthia H.
Sunset Zone 17, USDA Zone 9
If you do a soil test, you would be surprised how many come back with high or toxic levels of phosphorus.
Just because the soil has lots of phosphorus does not mean it is available to plants. Most of the phosphorus in the soil is bound to clay particles and organic matter until they are released by soil bacteria and made available to plants.
Sometimes even though there are high levels of phosphorus in the soil, the plants may still not have it available. pH, temperature, soil moisture and aeration, and salinity affect the rate of P mineralization from organic matter decomposition. Excess phosphorus is a concern because it can run off and pollute streams and oceans. Most of the runoff of concern is from concentrated animal farms like dairies, chicken farms, and piggeries.
Most sources of phosphorus is the mineral in rocks, fertilizer, and manures
https://filebox.vt.edu/users/chagedor/bi ... cycle.html
https://soils.usda.gov/sqi/assessment/fi ... _guide.pdf
https://aggieturf.tamu.edu/files-2005/ph ... Provin.pdf
For older lawns, phosphorus is only needed in small amounts so it is common for lawn fertilizer to have no or very low numbers of phosphorus.
typically lawn fertilizers are 21-0-0 or 16-4-4
Adding additional phosphorus to the fertilizer, or over fertilizing established lawns promotes more root growth and builds up thatch.
After many years of continually adding fertilizer, many soils have phosphorus in excess. Phosphorus that is built up in soil may take years to come down to acceptable levels so zero phosphorus fertilizers are in demand. When your soil test shows high or extremely high phosphorus levels the only thing you can do is not add anymore to the soil. This is hard to do, it is easy to find synthetic fertilizers without phosphorus but if you are using compost, manure, or vermicast, you may still be adding phosphorus to soils that don't need it.
Just because the soil has lots of phosphorus does not mean it is available to plants. Most of the phosphorus in the soil is bound to clay particles and organic matter until they are released by soil bacteria and made available to plants.
Sometimes even though there are high levels of phosphorus in the soil, the plants may still not have it available. pH, temperature, soil moisture and aeration, and salinity affect the rate of P mineralization from organic matter decomposition. Excess phosphorus is a concern because it can run off and pollute streams and oceans. Most of the runoff of concern is from concentrated animal farms like dairies, chicken farms, and piggeries.
Most sources of phosphorus is the mineral in rocks, fertilizer, and manures
https://filebox.vt.edu/users/chagedor/bi ... cycle.html
https://soils.usda.gov/sqi/assessment/fi ... _guide.pdf
https://aggieturf.tamu.edu/files-2005/ph ... Provin.pdf
For older lawns, phosphorus is only needed in small amounts so it is common for lawn fertilizer to have no or very low numbers of phosphorus.
typically lawn fertilizers are 21-0-0 or 16-4-4
Adding additional phosphorus to the fertilizer, or over fertilizing established lawns promotes more root growth and builds up thatch.
After many years of continually adding fertilizer, many soils have phosphorus in excess. Phosphorus that is built up in soil may take years to come down to acceptable levels so zero phosphorus fertilizers are in demand. When your soil test shows high or extremely high phosphorus levels the only thing you can do is not add anymore to the soil. This is hard to do, it is easy to find synthetic fertilizers without phosphorus but if you are using compost, manure, or vermicast, you may still be adding phosphorus to soils that don't need it.