Philom Bios Inc.
3935 Thatcher Avenue
Saskatoon, SK Canada S7R 1A3
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www.philombios.com

Phosphate & Crop Production

Crops require large amounts of phosphate as the basis of a good fertility program. It is required throughout the life stages of a plant, but it is especially important for early season growth. And like most nutrients, it must be in plant-available forms so as not to be the limiting factor in plant growth. Improving phosphate efficiency is one of the keys to healthy crop production.

Phosphate is a key nutrient in the drive for higher crop yields. For example, a 150 bushel per acre corn crop takes up 75 to 110 pounds of P₂0₅ per acre. A 50 bushel crop of soybeans takes up 40 to 50 pounds of P₂0₅ per acre and a 75 bushel per acre winter wheat crop takes up 50 to 55 pounds of P₂0₅ per acre.

Phosphate is responsible for:

• Improved root growth — for greater exploration of the soil that leads to better nutrient use efficiency.
• Faster emergence — to help establish yield potential.
• Better stand establishment — for better crop competition and stress tolerance.
• Earlier maturity — helps longer season crops yield closer to their full yield potential.
• Better water use efficiency — plants can better withstand drought stresses.
• Higher crop quality — improved seed set and more uniform seed fill.

Better Legume Nodulation and Nitrogen Fixation
Phosphate also plays a critical role in nitrogen fixation and enhances growth, yield and maturity in legume crops like dry beans, soybeans, peas, lentils, chickpeas and alfalfa. Research shows that adequate phosphate nutrition brings many benefits to legumes:

• More extensive root growth — provides greater opportunity for the development of nitrogen-fixing nodules.
• Faster development of active nodules — results in greater nitrogen fixation.

Phosphate and Crop Development
Yield potential will be compromised and delays in maturity and quality can occur without adequate phosphate nutrition throughout the growing season. Most crops begin to utilize phosphate early with uptake occurring even before the plant emerges from the soil and continues throughout the growing season until maturity. For example, concentrations of phosphorus must reach 0.5% in a five-leaf corn plant or yield potential will not be fulfilled.

However, young seedlings often have difficulty obtaining adequate phosphate because of a small root system, and the slow release of phosphate from cool soil. This problem is compounded when phosphate placement is limited by fertilizer toxicity in or close to the seed row.

Plant-Available Phosphate is Usually Low
Soils can be high in total soil phosphate but low in plant-available phosphate because much of the soil phosphate gets tied up in unavailable forms. As the crop takes up available phosphate, some of the unavailable phosphate is converted to available phosphate. However, this conversion does not take place fast enough to meet the demands of high yielding crops. As a result, crops will likely be deficient in phosphate.

Factors-affecting phosphate availability:

• Soils high in clay content tie up more phosphate than lighter soils.
• Phosphate is less available at colder soil temperatures.
• Availability is better in moist soils.
• Phosphate is more available in soils with a pH of 6.5 to 7.
• Plants with fibrous roots are better able to take up available phosphate through better soil exploration than plants with a tap root.

Phosphate Removal (lb. P₂O₅ per acre) by Crop