The Role of Phosphorus

  • Critical in early growth
  • Early root development
  • Early plant growth
  • Photosynthesis
  • Respiration
  • Energy storage and transfer
  • Others

More information

Placement of “P”

Liquid vs Dry

Polyphosphate vs Orthophosphate



Placement of Phosphate

Purdue University Research

Dr. Wilcox of Purdue University reported that 5 lbs/A of Phosphorus banded with the seed was equivalent to 20 lbs/A of Phosphorus two inches under the seed.

“The closer the starter is to the seed, the better the response is”

“However, a higher starter rate won’t compensate for the fertilizer being farther from the seed.”

The plots raise the question, if closer is better, why not put the starter in the furrow with the seed?



Waverley Farms – Yellow Grass, Saskatchewan


    TREATMENT                        MOISTURE           BU / ACRE      
ALPINE G22  @  3 gals +

22 lbs Banded dry Phosphate

12.3% 59.7 Bu
ALPINE G22  @ 5 gals 12.5% 58.9 Bu
ALPINE G22  @  3 gals 12.4% 58.5 Bu
22 lbs Banded Dry Phosphate 12.4% 55.7 Bu
No starter 12.4% 48.1 Bu





Study 1

12 lbs P2O5 seed-placed outyielded 60 lbs P2O5 banded

Study 2

ALPINE used on low P soils (8 – 18 lbs available)

No further response to the addition of phosphorus at 23, 46, 92, 184 lbs/acre broadcast



Corn – 5 leaf stage – ear initiation Stage


  • Can take up all the needed P in the first 4 weeks of growth (FARM FACTS)
  • Early root development critical to maximizing yields.

Importance of Early Season Phosphorous Nutrition

Cynthia Grant-Brandon Research Centre

  • Withholding “P” during the early stages of crop growth limit crop production
  • Critical “P” supply – tiller production barley – first 4-6 weeks of growth
  • Important to manage “P” – ensure early season access by the crop
  • Optimal method – supplying “P” early – near/with seed

Liquid vs. Dry

“Dry Phosphorus fertilizer is generally quite inefficient in terms of actual fertilizer phosphorus that gets into the plant. Various experiments indicate perhaps 5 to 8% is about all we expect with 30% being quite high. It will be more often below 10%.” Source: The Cooperative Extension, University of Nebraska


Liquid Advantages as stated in Bertrand/Holloway Research-Australia

  • The differences between the efficiency of fluid vs. granular fertilizers were significant -especially in clay soils
  • Fluid fertilizers increased by 42% the amount of available “P” in the soil compared to granular applications
  • Fluids are at least 20% more efficient than granular


Here are a few points worth considering:

  1. We would consider phosphate to be the most important nutrient to be in the liquid form since it is the most critical nutrient in early growth above and below the ground. Cold dry soils in the spring are where a seed placed plant available liquid phosphate fertilizer really shines. Compared to a dry granular phosphorus that can still be in granular form in June when soil moisture is limited.
  2. Greater amounts of Nitrogen are needed later in the season and should be placed away from the seed to insure there is no seed burn from the nitrogen. We recommend the seed placed liquid ALPINE phosphorus and a side banded nitrogen program –this gives the farmer the best of both worlds – early plant growth from the seed placed phosphorus and no burn from the side banded Nitrogen
  3. Placement of phosphate is extremely critical to maximize early growth and root development. Endless amounts of research point to the only place to put phosphate is with the seed. A lot of guys using a complete liquid program are mixing the phosphorus with the nitrogen and placing the blend away from the seed which reduces the efficiency of the phos.
  4. One big reason our customers like switching their phosphorus program to liquid is that it frees up that much more space in their air carts for more dry nitrogen and since we find only 3-4 gals of a plant available phosphorus with the seed of most crops is enough the farmer does not a very big liquid tank added to the cart. A 500 gal tank @ 3 gals/acre will cover a quarter section.
  5. Most of our customers use dry nitrogen since 46% urea is much more concentrated than 28% UAN. Although some customers will opt for a complete liquid system for the overall convenience.
  6. If your soils require micronutrients adding say 1 litre of  Zn or Mn to 3-4 gals of ALPINE liquid phosphorus will evenly disperse the micro across every ft of every row compared to trying to add a micronutrient into your dry blend. We have seen excellent results adding micros into the seed placed ALPINE at planting time where the soil is deficient in that micro..
  7. Our same seed placed liquid phosphorus product can also be used as a great foliar product and since the farmer has in on farm in bulk it is much cheaper than any packaged foliar product on the market. We really like following up our starter phosphorus program with 1-2 litres of our product foliar at crop spray time. It gets more nutrients into the plant at a time when environmental and chemical stresses can be going against the crop.
  8. Quality of raw materials must always be considered. One problem with the fertilizer industry as a whole is the NPK analysis is the only thing that needs to be guaranteed. The level of impurities and the raw materials used to make the product are never considered. We have found a very wide range of impurity levels in liquid fertilizers. There are what is known as “Spent Acids” that make their way into the fertilizer industry from the bright dipping car part industry. These are very cheap raw materials but can cause problems with germinating seeds due to the high levels of impurities like aluminum. Dry phosphorus can even have as much as 10,000 ppm of Aluminum where our product will run closer to 1500 ppm. Aluminum at high levels can be toxic to root growth – not a good idea for a seed placed fertilizer.
  9. When applying phosphorus we look at a concentration per ft of row. We will recommend more product on narrower rows because you have more liner ft of row per acre in a 7” row vs a 10” row. Phosphorus is your starter part of your program and concentration per ft of row needs to be considered.
  10. Cost per pound of plant food is always an issue with liquids vs dry. With nitrogen I am not convinced there is enough advantage with liquid N over dry N to cover the added cost per lb. but with phosphorus there is no doubt that a small amount of very plant available liquid phosphorus seed placed on crops will perform better than larger amounts of dry phos. So the cost per acre with ALPINE is usually similar to a dry phosphorus program since we normally recommend less lbs of phosphorus per acre than is normally used in a dry phosphorus program. We recommend 8-10 lbs of actual phosphorus as ALPINE where most dry programs are 20-30 lbs actual phos.


Polyphosphate vs. Orthophosphate

Plant uptake of Phosphate

  • Plants absorb P as Orthophosphate ions H2P04- and HP042-
  • Polyphosphates are a chain link molecule of orthos and are not available to the plant until conversion.

Source: Farm Facts –Phosphorous fertilization in crop production and TVA.

Polyphosphate Production

Super Phosphoric Acid (SPA) combined with NH3

Processed through a Pipe Reactor = 10-34-0 or 11-37-0

Chain Link Molecule of Orthophosphate

Unavailable to the plant in that form

Must convert to orthophosphate

Time and Temperature