Phosphate Fertilizer

Phosphate is an essential part of plant structure and development. It is a component of both DNA and RNA, the genetic memory unit of all living things. It is part of the ATP units in plants which are essential for the transfer of energy in plants. It is in our soils naturally but has no way to be replenished. What we remove with plants, we must replace with another source like manure or fertilizer. If not, our soils will become deficient. In our area, we are seeing declining levels of phosphate in our soils. Every crop that we harvest removes phosphate from the soil. With wheat, the removal rate is 0.6 pounds of P2O5 for every bushel that is grown. For a 60 bushel crop of wheat that means that 36 pounds of P2O5 phosphate must be added to the field. Alfalfa is similar to wheat in its removal rate with a 3 ton crop. For canola, the removal of phosphate goes to 0.9 pounds per bushel. This means that we need to add 54 pounds of P2O5 just to replace what this crop took out of the ground. For producers growing top yields, the amount of phosphate required is high. It is easy to see why the levels of phosphate are going down in our area. It is an essential nutrient that must be replaced on a constant basis. If it is not replaced, the crop yields will go down. Manure is an excellent way to replace soil phosphate as well as other nutrients. The problem with manure is that we do not have enough livestock in this area to meet the requirements of our crops. If we want to see the yields maintained in our area, we have to be using commercial fertilizers. With phosphate the most effective way to apply it is with the seed in a band. Putting the phosphate by the seed will allow the plants quick access to the nutrient. Putting phosphate in a band reduces the amount of phosphate tied up in the soil. This helps increase the effectiveness of the product that is applied. Care must be taken not to put too much phosphate by the seed because toxicity to germinating seeds can be an issue. This means that producers must look at other ways to apply additional phosphate, especially with small seeded crops. Putting phosphate in a mid-row band or in a band applied as a separate operation than seeding can be an effective method of placement. If the phosphate is put in a band that has over 70 pounds of actual nitrogen, the phosphate may not be available the first year. Broadcasting on the soil surface is the final method of application. With this method, the product is the least available because of soil tie-up and distance from the roots. Phosphate will stay in the soil and be there for future years using this method of application. Phosphate is essential for plant growth. Adding phosphate is essential for plant growth. Be sure to include adequate amounts of this nutrient in your fertilizer plans.


By Dave Cubbon, P Ag