LaMotte SMART 2 Electronic Soil Lab - Manual (Page 73)

PHOSPHORUS
ASCORBIC ACID REDUCTION METHOD CODE 3653-SC
QUANTITY CONTENTS CODE
60 mL *Phosphate Acid Reagent *V-6282-H
5 g *Phosphate Reducing Reagent *V-6283-C
1 Pipet, 1 mL, plastic 0354
1 Spoon, 0.1 g 0699
*WARNING: Reagents marked with a * are considered to be potential health hazards. To view
or print a Material Safety Data Sheet (MSDS) for these reagents see MSDS CD or
www.lamotte.com. To obtain a printed copy, contact LaMotte by e-mail, phone or fax.
Phosphorus is necessary for the hardy growth of the plant and activity of the
cells. It encourages root development, and by hastening the maturity of the
plant, it increases the ratio of grain to straw, as well as the total yield. It plays
an important part in increasing the palatability of plants and simulates the
formation of fats, convertible starches and healthy seed. By stimulating rapid
cell development in the plant, phosphorus naturally increases the resistance to
disease. An excess of phosphorus does not cause the harmful effect of excessive
nitrogen and has an important balancing effect upon the plant.
RANGE: 0.00-99.00 lb/acre Phosphorus
METHOD: Ammonium molybdate and antimony potassium
tartrate react in a filtered acid medium with dilute
solution of PO4-2 to form an
antimony-phosphomolybdate complex. This complex
is reduced to an intense blue colored complex by
ascorbic acid. The color is proportionate to the
amount of phosphate present. (Only orthophosphate
forms a blue color in this test.) Polyphosphates (and
some organic phosphorus compounds) may be
converted to the orthophosphate form by sulfuric acid
digestion. Organic phosphorus compounds may be
converted to the orthophosphate form by persulfate
digestion.
INTERFERENCES: High iron concentrations can cause precipitation of
and subsequent loss of phosphorus.
SMART2 SOIL MANUAL 1.07 73