How fast a field’s soil test phosphorus falls without phosphorus, or builds with fertilizer, manure or biosolids.
Decision aid only. It does not replace the Phosphorus Management Tool or a nutrient management plan.
Your field and soil test
Choose the laboratory first: it decides which units you can pick and how your number converts. Then enter the number in the unit printed on your report. Pounds per acre is not simply twice ppm, and it is P₂O₅ at some laboratories and P at others; the button says which.
Mehlich-3 P, reported as:
Your target
The soil test you would like this field to reach. UMD Extension’s optimum range is FIV 51–100, so 100 is the usual target; above it, added phosphorus most likely will not pay. The PMT stops applying below FIV 150.
Your rotation
1. Pick a crop for each year; use “+ double crop” for a second crop in the same year.
2. Check the yield or type your own. For a crop not on the list, choose Other crop and enter what it removes, in lb P₂O₅ per acre.
Count only what leaves the field. Grazed forage returns most of its phosphorus to the pasture in manure, so enter the hay or silage taken off, not what the animals eat.
Save and share
Keep saves the field in this browser only. Copy link carries every setting. Share opens your email, or your phone’s share menu, with the summary and a link. Your field stays on this device; the page sends only anonymous counts of how it is used.
Soil test P then
—
Years to target
—
The chart could not be drawn in this browser. The figures above are not affected.
Who’s using this?
Optional, asked once.
© Gurpal Toor, University of Maryland. Developed in Partnership with the Maryland Department of Agriculture.