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Phosphorus Calculator Under Development

Aphosphorus calculator is being developed for wheat, barley and canola grown in Manitoba to help farmers assess the economics of applying phosphorus, Rigas Karamanos, Viterra’s agronomy manager, told the 54th annual meeting of the Manitoba Soils Society in Winnipeg Feb. 3.

The phosphorus calculator will work much like the nitrogen calculator, an interactive, spreadsheet- based, computer program, released in 2009.

Viterra and Manitoba Agriculture, Food and Rural Initiatives (MAFRI) developed it, with funding from the Agri- Food Research &Development Initiative (ARDI) and Western Co-operative Fertilizers Ltd.

A release date for the calculator hasn’t been set, MAFRI soil fertility specialist John Heard said last week.

With the nitrogen calculator farmers enter how much soil test nitrogen is already in their fields, the price of nitrogen and the program spits out the optimum economic rate of nitrogen based on yields under arid, dry and moist growing conditions.

The phosphorus calculator will offer three application options based on a rate that’s considered sufficient (conservative), a cut rate or a rate based on the amount of phosphorus the crop will remove, Heard said.

“We want farmers to think deeper than looking at one black and white number,” he said.

“We need to build in flexibility. Farmers farm for more than one year. That sufficiency approach is based on one year’s economics.”

The phosphorus calculator is a tool for farmers when applying phosphorus, not a regulation, Heard said.

The phosphorus calculator is based on the existing recommendations for phosphorus applications in crops, Karamanos said.

Based on 47 site-years of data applying phosphorus where there’s less than five parts per million of phosphorus already in the soil there will almost always be a yield increase when additional phosphorus is applied, he said.

Adding more phosphorus to soils with six to 10 ppm results in increased yields 71 per cent of the time.

Soils with 10 to 20 ppm of phosphorus will produce higher yields 50 per cent of the time when more phosphorus is applied. [email protected]

About the author


Allan Dawson

Allan Dawson is a reporter with the Manitoba Co-operator based near Miami, Man. Covering agriculture since 1980, Dawson has spent most of his career with the Co-operator except for several years with Farmers’ Independent Weekly and before that a Morden-Winkler area radio station.



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