CHAMBERSBURG, Pa. — Fertilizers have always been an expensive, yet necessary, crop production input. In a typical year with average prices, fertilizers are only preceded by seed as the most expensive input in our production budgets. Currently, fertilizer prices are 2-3 times higher than what we’ve experienced in recent years. A few considerations for those looking to manage soil fertility without jeopardizing yields:
- If you do not have a recent soil test, plan to take one as soon as possible. Soil testing may be accomplished any time that the ground is unfrozen and fit for sampling. The Franklin County Extension office has soil testing kits for sale, $9/sample. There are other laboratories that offer this service, too. Plan to soil test this fall or spring to best understand current soil pH and fertility status of your fields.
- Prioritize liming over fertilizers if soil pH is well below optimum. Liming is relatively low cost and brings major returns to our agronomic systems. Optimal soil pH influences root growth, the availability of most nutrients, and the efficacy of crop protectants such as herbicides. For most of our forages and grains, optimal pH will be between 6.0 and 7.0, with few crops such as oats tolerating more acidic conditions. Pay close attention to lime quality and recognize that even a high quality ag-lime will slowly correct soil pH over the course of ~3-6 months.
- Fertilize phosphorous and potassium at crop removal rates if soil levels are in the below optimum range. This sufficiency approach of providing only enough nutrients to meet crop needs as opposed to building up soil nutrient reserves is an economical strategy for short term management. A drawback to this approach is that producers should soil test more frequently to dial-in soil fertility status and ensure that forages and grain aren’t being shortchanged, leading to yield losses from deficiencies.
- Band phosphorous fertilizer belowground for increased efficiency. Broadcasting maximizes contact with and fixation by soil minerals; they are also generally less accessible for root uptake. Applying phosphorous fertilizer with a planter is an ideal approach; monomammonium phosphate (MAP – 11-52-0) and ammonium polyphosphate (10-34-0) are good starter fertilizers. Potassium, which easily diffuses through the soil, can be broadcast on the soil surface. Because muriate of potash fertilizer has a high salt index and can injure young seedlings, the application rate in a starter band should be limited.
- Manure is a valuable source of nitrogen, phosphorous, and potassium. Make efforts to maximize the efficiency of manure nutrient sources. If possible, to conserve manure nitrogen, consider injection. Volatilization can be reduced when applications are made with air temperatures of < 45 degrees F. Applying closer to late winter and early spring can help mitigate losses that may occur during the winter. Reduce the risk for runoff during winter applications by avoiding fields with steep slopes, high erosion rates, poorly draining soils, or fields close to water sources.
When fertilizer prices return to ‘normal’ in the future, it will make sense to return to the traditional approach of “build and maintain” recommendations, working to replenish some reserves used up during this period of high fertilizer prices or building nutrients up into an optimum range. Doing so will allow your soils to provide a buffer that gives you some additional flexibility in navigating short-term fertilizer price spikes.
–Brittany Clark, Penn State Extension