Fertilizing This Fall
By Will Scott
While harvest is top of mind for many farmers, now is also the time to start thinking about fall fertilizer applications. Fall fertilizer is an important step in managing your fields’ health, replenishing nutrients that were depleted during the previous year, and ensuring that your fields are prepared to produce high yields for your next crop season.
Based on declining nutrient trends we’re seeing in recent soil tests, and the unfavorable weather effects we’ve seen throughout 2019, we are anticipating a return to 2017 nutrient levels for fall application. Due to the abnormally wet season last year, phosphorus and potassium levels were down roughly ~30% from 2017. Historical testing also shows soil nutrient levels are being depleted and falling below optimum levels at a 10% rate, year over year.The decline in optimal soil nutrient levels is preventing crops from achieving maximum yield potential. With results trending like this, it is even more crucial to focus on fall fertilizer in preparation for the 2020 season.
All that said, fall fertilizer applications can present many challenges. If done correctly, fall-applied Nitrogen, Phosphorus, Potassium, Lime and Sulfur will provide logistical, agronomic, and economic benefits. It’s all about focusing on the specific nutrients to be applied.
Nitrogen: Some of the biggest risks of applying nitrogen in the fall are gaseous losses, nitrate leeching, and runoff. To avoid these problems, apply Nitrogen when soil is 50° F or less and the ground isn’t frozen. Additionally, it is also important to properly coordinate the form of nitrogen applied with the time of year of application. The best fall-applied nitrogen sources are ammonia, ammonium, and urea. And while nitrogen loss can still occur, one way to prevent it is by using nitrogen stabilizers. Innvictis Crop Care’s N-Veil® prevents gaseous losses and Preserve N™ prevents losses through leeching.
Phosphorus: Of all the macro nutrients, Phosphorus has the least mobility in the soil profile. Phosphorus also has the potential to tie up when the soil pH is above 7.3 or below 5.5. Knowing what your soil pH is can help determine what solution is needed for proper application timing of phosphorus. Soil testing will help identify these pH levels. If a field’s pH levels are acidic, then applying Lime to increase the soil pH is recommended. If a field’s pH levels are high, using sulfur to lower the pH is recommended.
Lime: Lime consists of calcium carbonate and is used to neutralize soils by transferring molecules to the soil. In short, Lime neutralizes soil pH by giving up two oxygen molecules to the soil which combines them with a hydrogen molecule to form H2O, or water. With a lime application, soil pH levels can increase 0.3-0.5 pH points a year, subject to the effects of environmental conditions such as drought or saturation.
Sulfur: Sulfate is a secondary nutrient and anion not held in the soil profile. This means that sulfates can leech out of soils but at a less rapid rate than nitrates. As with potassium applications, soil texture is important when considering if a fall or spring application of Sulfate is recommended.
Potassium: Potassium is a macronutrient and cation. This means it’s needed in greater relative amounts and will bind to the soil profile. Start with a soil test to determine if a fall or spring application is recommended. Also, gauge base soil saturation levels. Soil texture is a factor that should also be considered. Course textured soils (CEC6-10 or less) tend to leech potassium and would warrant a spring application.
Above all else, soil sampling is critical to determining the appropriate mix and timing of nutrient applications. Reach out today to your local sales representative or Pinnacle’s customer service team to create your fall fertilizer plan.
As Pinnacle’s Tech Services Manager, Will Scott brings his industry expertise to the organization’s product offerings. Since joining Pinnacle Agriculture in 2012, Will works closely with research and development, proprietary brands and procurement teams to ensure we are delivering the best possible product to our customers.