Outsmarting Your Fertilizer “Competition” to Improve Uptake Efficiency By DR. KARL A. WYANT | Director of Agronomy at Nutrien, Western Region Certified Crop Advisor Board Chair
O
ne fortunate aspect of working in agriculture is that hot summer days are soon followed by harvest season and the onset of nicer weather. Now is the time to start thinking about postharvest soil fertility maintenance. Dry, granular phosphorus and potassium fertilizer products (e.g., monoammonium phosphorus (MAP: 11-52-0); sulfate of potash (SOP: 0-0-50); and muriate of potash (MOP: 0-0-60)) are popular choices for postharvest fertility work and a cornerstone of annual nutrient budgets for many crops.
These fertilizer formulations are popular with growers as they can apply bulk nutrients to help maintain soil fertility and get a jump start on supporting the next crop cycle. However, fertilizer prices, at the time of this writing, are expected to remain elevated due to a perfect storm of global events outside much of our control. With that in mind, there are various sources of
A Grower’s Go-To Information Resource
Figure 1. Estimates of soil-applied fertilizer efficiencies (amount used by crop relative to how much was applied total to the soil.) Phosphorus and potassium have a relatively lower use efficiency compared to nitrogen due to some of the factors listed in this article. Anticipating and counteracting soil “competition” can help push up fertilizer use efficiencies and drive a higher return on investment for the grower (Fixen et al. 2014).
“competition” that prevent the uptake of the nutrient by the plant, which leads to inefficiency in fertilizer use, reducing optimum fertilizer return on investment (Figure 1). In a perfect world, 100% of your fertilizer application would be used by the crop to produce yield, return on investment would be maximized, and fertilizer losses would be minimal. However, as Figure 1 shows, use efficiency of fertilizers vary greatly by nutrient category. In this article, we will name the various efficiency loss pathways, or “competition”, for your phosphorus and potassium fertilizer applications so you can work with a crop advisor to try and work around them. Before we jump in, let’s start with some phosphorus and potassium 101.
Why Crops Need Phosphorus and Potassium
Nutrien-eKonomics.com is an easy-to-use website and app featuring return on investment calculators, crop management tools, geographic soil test data, industry expert advice and concise research – all designed to help maximize grower returns. • Nutrient ROI Calculator • Growing Degree Days Calculator • Nutrient Removal Calculator • Rainfall Tracker
Nutrien-eKonomics.com Available: Apple Store & GooglePlay - eKonomics by Nutrien
10
Progressive Crop Consultant
Phosphorus and potassium are plant macronutrients that are required in large quantities by the crop to produce a high-quality yield. However, phosphorus and potassium play different roles in the plant. Phosphorus is a crucial component for converting solar energy into food, fiber and other plant products. Furthermore, phosphorus also plays a key role in the metabolism of sugars, energy storage and transfer, cell growth and the transfer of genetic information. An interesting bit about phosphorus is that one can point out the element embedded in the actual chemical structures the plant is using to create yield. For example, you can point to the actual phosphorus that is used to build the biological currency plants use to “pay” for work (ATP) and the phosphorus backbone that all crops use to construct their genes (DNA). On the other hand, potassium is much more difficult to point out in the crops’ molecular portfolio. However, we do know that potassium is still needed by the plant to support high yields. Briefly, potassium increases crop yield, improves crop quality, reduces disease and decreases risk of lodging and branch breakage, etc. Except for nitrogen, plants often require
September / October 2022