Soil’s history: A solution to soluble phosphorus?

Past applications of phosphorus fertilizers affect availability to crops.

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A team of researchers from the Food and Agriculture Organization of the United Nations estimated the 45 million of phosphorus fertilizers will be utilized throughout the world in 2018.

A great amount of this phosphorous will be utilized to soils that already have received phosphorous fertilizers previously. However, a great amount of it could be redundant.

Jim Barrow, a scientist at the University of Western Australia, states, “Previous application of phosphorus fertilizers increases the effectiveness of subsequent applications.”

He added, “Better understanding soil phosphorus dynamics can have many benefits. It could lead to the more judicious use of phosphorus fertilizers. At a world level, phosphorus is a limited resource. We need to use it wisely.”

Immoderate application of phosphorous fertilizers not merely pollute water at a local level but also a purchase is not within means for farmers.

Abhijit Debnath in his laboratory.  CREDIT Abantika Debnath.
Abhijit Debnath in his laboratory.
Abantika Debnath.

Barrow states, “If farmers use only as much as is required, it will help the environment.”

“It will also save them money.”

When phosphorous fertilizers are utilized in soils only fraction is absorbed by the plants. This happens because of the phosphorous that stuck on the soil grains whereas a small amount left in the solution.

Barrow states, “When the portion in solution is high, plants can get phosphorus quickly from the soil.”

“Low fertilizer application rates are sufficient.”

Barrow pointed out that when the compound utilized in fertilizers, Phosphate, can react with and penetrate soil particles it’s scarcely available to plants. This is a major reason why farmers have to reapply phosphorus fertilizers.

But this is advantageous, Barrow explains, “When phosphate penetrates soil particles, it makes the soil particles more negatively charged.”

Because of the similar charges repel each other, negatively charged soil particles repel the negatively charged phosphate. It shows there is more in solution and plants get it faster and so need fewer fertilizers.

A group of researchers involved in the researchers explored whether phosphate would continue to penetrate soil particles at the same rate over time. They provided the reason that would decrease as the negative charge built up.

Barrow states that when a great amount of phosphorous has been applied over time the absorption of phosphate slows down and eventually will stop. And you only need to replace phosphate utilized (and removed in produce) in last year.

It is analogous to repairing a gravel road where potholes and other gaps need to be filled before a sleek, functional top layer is utilized.

During their research, Barrow worked with colleagues at Bidhan Chandra Agricultural University in West Bengal, India. They applied to soil from a field about 65 miles west of the city of Kolkata, India. To duplicate phosphorous utilization over time, the researchers applied phosphorous and then kept the soil140°F (60°C) for more than a month.

Barrow says, “It is quite slow at ordinary temperatures.”

“This way we don’t have to wait around for years before we can do an experiment.”

It would be an aid to farmers utilizes phosphorous fertilizers more effectively. It would enable farmers to reduce expenses.

Barrow says, “But these findings need to be conveyed to farmers.”

“The effectiveness of the soluble phosphate fertilizers has been grossly underestimated.”

The study is published in the Soil Science Society of America Journal.