LETTUCE GROWTH AND PHOSPHORUS LEACHING IN MEDIA AMENDED WITH PHOSPHORUS-TREATED MAGNETITE

Magnetite was examined for use as a medium on which to bind phosphorus (P) for the purpose of reducing P leachate from container grown crops.
Magnetite was acid washed, pH adjusted to 5.0, and then shaken in a 10,000 mgP·L^-1 solution.
The P-magnetite was chemically characterized to determine P content (176 mgP·kg^-1 magnetite). A greenhouse experiment was performed to determine the accessibility of the P from the P-magnetite to the plant and the amount of P leachate. ‘Valmaine’ Romaine lettuce Lactuca sativa was sown into 5.5 inch standard containers and treated with one of the following: 250 g P-magnetite (44 mg P), 150g P-magnetite (26mg P), 50g P-magnetite (8.8mg P), 150g untreated magnetite, 3g 15-9-12 Osmocote (119 mg P), 21-5-20 constant liquid feed (5.25 mg P/fert. event), and no treatment.
For four weeks, weekly leachate samples were taken and analyzed for P content.
At the completion of four weeks, the shoots were dried and weighed.
The constant liquid feed treatment had the highest P leachate and shoot dry weights.
Osmocote and 150 g P-magnetite had similar P leachate, and the shoot dry weights for the 150 g P-magnetite treatment were significantly higher than for Osmocote.
This study demonstrated that P from amended magnetite is accessible for uptake by plants and leachate was reduced using P-magnetite compared to a constant liquid feed.

XXVI International Horticultural Congress: Toward Ecologically Sound Fertilization Strategies for Field Vegetable Production

A. Graham, J.H. Gillman, C.J. Rosen

slow-release, fertilizer, eutrophication, runoff

https://doi.org/10.17660/ActaHortic.2003.627.21