Keys to Profitability: Fall Phosphorus and Potassium Fertilizer Applications

Our soil is stressed. With increased yields reaching record levels, crops requiring more nutrition than ever before, and challenging weather conditions on top of it all, fertilizer application is a must. However, the crunched 2019 spring season saw the challenge of not only trying to get a crop in the ground but also ensuring the soil had the right nutrients to sustain that crop.

Taking action on next year’s crop this fall remains crucial to ensuring soil has the right nutrients for optimal production. According to Agtegra Agronomy Tech Service Manager Brad Ruden, fall application remains crucial to crop profit potential: “Crop nutrition is the single factor that can affect more than 60 percent of production potential,” Ruden says. The importance of taking action this fall and working to ensure your soil has the right nutrients for optimal production cannot be stressed enough.”

Crop nutrition starts with having a good understanding of your soil. “Determining how often you should soil-sample and using ‘best practices’ are key to a balanced crop nutrition program. In addition, calculating crop removal using the available online tools can greatly increase the efficiency of getting the right nutrient on the right acre,” Ruden says. However, with the drastic weather patterns of 2019, yield, opportunities for soil sampling and fertilizer applications have been greatly affected. Ruden notes that some soil test recommendations have set the bar too low on potash levels, allowing significant reductions in soil K levels, at times with yield-robbing effect. Some producers consider decreasing phosphate and potash applied per acre to try maximizing profits in the short term, which can limit yield and cost more in the long run due to the key role phosphorus (P) and potassium (K) play in overall crop nutrition.

Why P and K?
Phosphorus plays a critical role in photosynthesis, respiration, energy transfer and storage, root growth, rapid crop establishment, sugar formation, starch accumulation and soybean nodule development and function. Double digit up to phosphorus soil test levels in the teens are minimum levels for maximum soybean production, for example. Potassium levels are key to increased stalk strength, ear retention, nitrogen movement and utilization and improved drought tolerance. Another key factor in these two nutrients includes their decreased mobility. Applying less mobile nutrients such as P and K in the fall allows more mobile nutrients such as nitrogen and sulfur to be applied in the spring, which can help meet the crop’s demands and achieve sustainable plant nutrition management.

With many producers not getting a crop in the ground due to weather creating extreme challenges in the region, application of phosphorus may be more important now than ever. “The soil’s ability to help plants tap into available phosphorus will actually go down for the following crop, a condition called Fallow Syndrome,” Ruden states. This condition occurs due to the lack of plant roots in the soil, which causes reduced activity of soil mycorrhizae fungi. “To compensate, increased phosphorus fertilizer applications may be needed, even at consistent soil test levels,” Ruden adds.

Fall application opens the door for numerous opportunities in terms of crop yield potential, field efficiency, and accurate nutrient timing. Not only are there several options for how fertilizer can be applied in the fall, but the application alleviates the stress of unnecessary planting delays and ensuring P and K are established in the field long before spring applications of other fertilizers. Because P and K are non-volatile, low-leaching nutrients and have minimal environmental losses, fall application enables maximized field efficiency in terms of timing other fertilizers and field work.

Contact your Agtegra Agronomist with questions on Fall P and K applications today.

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