The Importance Of Early Season Phosphorus Nutrition 

Lyle Cowell

Lyle Cowell

Nutrien

Senior Agronomist

Lyle Cowell is based in northeast Saskatchewan, where he has spent his career in agronomy with a focus on better soil management.  Lyle has always had the goal of connecting the three points of good research, agronomy extension and farm gate advice and application of soil fertility principles.

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Early season supply of phosphorus from soil or fertilizer is essential for adequate crop nutrition. This paper reviews past research to highlight the value of this practice. Phosphorus plays a key role in energy reactions in plants, which are very important in the early season as seedlings begin to grow rapidly. In fact, deficiency of phosphorus early in the growing season will impact yield far more than later in the season. Plants have developed to avert phosphorus deficiency through rapid root growth in soil regions rich in phosphorus, symbiotic relationships with mycorrhizal fungi, and the release of acidic exudates from roots to solubilize soil phosphorus. Plants are also able to transfer phosphorus within tissue so that early uptake can be transferred to the developing plant later in the season. 

In addition to the requirement of phosphorus early in the season, fertilizer phosphates are very reactive and will form less soluble compounds after application. Strategies are then required to provide a ready supply of fertilizer phosphorus to the young developing plant. 

Seeding equipment that can place phosphorus fertilizer in bands in or near the seed row improves early access to root systems and reduces the rate of precipitation of the phosphates.  In very deficient soil it may be advised to increase phosphorus fertilizer rates to maintain a higher background level of soil phosphorus. Some crop species are more efficient than others in utilizing a band of phosphorus fertilizer, so overall field management should consider the entire crop rotation. For example, canola appears to be more efficient than either soybean or flax in phosphorus fertilizer use.  

There may be genetic potential for breeders to select for more efficient phosphorus use or there may be biological products that could enhance uptake, but the first and most important step will remain to provide an adequate rate of phosphorus early in the growing season. 

Sources: 

Grant, C. A., Flaten, D. N., Tomasiewicz, D. J. and Sheppard, S. C. 2001. Can. J. Plant Sci. 81: 211–224. 

https://cdnsciencepub.com/doi/abs/10.4141/P00-093