Wednesday, November 6, 2013

Soil P

Our email group has discussed phosphorous extensively this year.  A farmer asked why his soil lab suggested he may want to include more P for his crop when it is below 50 degrees.  Purple corn is well known by farmers from a lack of phosphorous at cooler temperatures.  The subject of phosphorous is not black and white.

"PHOSPHORUS (P) is an immobile nutrient. So when
a P fertilizer material is applied to the soil it remains in
place. This is generally true, but as with most generalizations
there is more to the story and certainly exceptions to
the generalization. The following discussion is intended

put P mobility in perspective.

Fertilizer Phosphorus

The chemical form of P in fertilizer materials is

phosphate (H2PO4

-, HPO4

-2 or PO4

-3 ). Regardless of what

fertilizer we add to soil, whether it is a dry product such as
concentrated superphosphate (0-46-0), diammonium
phosphate (18-46-0), monoammonium phosphate (11-52-
0), or a solution product such as ammonium
polyphosphate (10-34-0), for all practical purposes the fate
of soil P is ultimately the same.

From the Farm to Plate Manual:
"Phosphorous acts as a catalyst in the conversion of nutrients.  Some potential benefits of phosphorous may include more vigorous and rapid growth, early root growth, better development and quality of grain, quicker maturity, increased nitrogen uptake, increased mineral content and higher sugar levels in the plant.  Phosphorous also promotes energy release in cells, cell division and enlargement, photosynthesis and neutral pH.  Phosphorous is contained in the DNA and is non-toxic to the plant.  Good sources of P include MAP, Idaho phosphate, North Carolina phosphate and soft rock phosphate.

Optimum levels are 175 pounds per acre with a 2 part P to 1 part K ratio for grass crops.  Legumes need more potassium in relation to phosphorous."

I am spreading soft rock phosphate this year.  How will you address the phosphorous needs of your crop?

Here is a great video narrated by Baxter Black about the importance of wheat to world and American agriculture.  The farmers in the video pretty well understand the importance of phosphorous to their wheat crop.  They also understand the value of teaching our children these principles.

Ed Winkle

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