Soil Management

Canadian Researchers Look at Phosphorus Management in Northern Great Plains

eKonomics News Team

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For more than a decade, responsible on-farm nutrient management has followed the globally-recognized guiding principles of nutrient stewardship…the 4Rs. Applying the right source of fertilizer at the right rate, the right time, and the right place encourages sustainable and responsible use of crop nutrients.

But not all nutrients are equally available to growing crops, and this impacts the 4R principles for phosphorus management. Phosphorus doesn’t move much in the soil. It stays mostly where it’s placed during application, forcing young plants to use their roots to grow towards the phosphorus in the soil.

In regions where soils are colder at planting, and growing seasons are shorter, the dynamics of phosphorus and 4R nutrient stewardship are affected – and must be managed accordingly. This is especially true in the Northern Great Plains region that includes the western prairie provinces of Canada, growing regions in South Dakota, North Dakota, Montana, and northern parts of Wyoming and Nebraska.

4R Graphic Illustration

And when you factor in the changing farming practices – more reduced tillage, new crops and high-yielding cultivars, intensification of crop rotation, and new fertilizer products – this further impacts the changing face of phosphorus management.

Adding another R

The 4R principles are not static and must be evaluated and updated based on changing conditions. Farmers and advisors need to consider a fifth R, the right science-based information, to make good decisions about how nutrients are managed.

That’s where two Canadian soil scientists come in. After more than 25 years since a comprehensive review of available phosphorus management information had been done, Dr. Cynthia Grant, and Dr. Don Flaten of the University of Manitoba, set out to review the scientific literature. Their goal was to ensure the current 4R management of phosphorus is sustainable from an agronomic, economic, and environmental standpoint.

Phosphorus in cold soil       

Phosphorus is an essential plant nutrient, and one of the most limiting to crop production, after nitrogen, in the Northern Great Plains. Phosphorus plays a critical role in energy transfer, photosynthesis, and cell division – activities all necessary for seed to germinate, grow, and yield. Plants need phosphorus in the earliest stages of growth. But under cold soil conditions, when young plants can’t access enough phosphorus, crop growth suffers, and overall crop yield will be negatively impacted.

These factors make it all the more important to ensure phosphorus management, under the 4Rs, optimizes plant growth potential, and represents sustainable practices.

Insights for managing phosphorus

Here are some of the key messages from 4R Management of Phosphorus Fertilizer in the Northern Great Plains: A Review of the Scientific Literature.

Select a phosphorus management practice that suits each individual crop since crops differ in their phosphorus demands, sensitivity to seed-placed fertilizer, and ability to access phosphorus from fertilizer bands or the soil.

Under conventional or reduced tillage, subsurface banding in or near the seed-row at seeding (at rates based on soil testing) will normally provide the most environmentally and economically sustainable results.

Balance phosphorus supply with phosphorus removal over the long term to avoid excess depletion or accumulation.

Realize the maximum benefit of 4R management of phosphorus fertilizer when you also follow agronomic practices to produce a healthy, vigorous crop.Ensure all nutrients, including phosphorus, are available in an adequate supply from the soil or fertilizer applications to ensure optimum crop yield and efficient use of phosphorus

Read more here about phosphorus uptake in cold, wet conditions.


4R Management of Phosphorus Fertilizer in the Northern Great Plains: A Review of the Scientific Literature, Cynthia Grant and Don Flaten, University of Manitoba, July 2 2019.