– Chris Teutsch and John Grove, UK Research and Education Center at Princeton
Figure 1. Fertilizer price trends for nitrogen (urea), phosphorus (DAP) and potassium (muriate of potash). In the last 12 months fertilizer prices have increased more than 50% (Data from Russ Quinn at DTN).
In the last year, the cost of fertilizer had increased more than 125%, 85%, and 115%, for urea (nitrogen), diammonium phosphate (phosphorus), and muriate of potash (potassium), respectively (Figure 1). The price of nitrogen could continue to increase due to the idling of N manufacturing capacity caused by weather issues and increased natural gas and shipping costs. Nitrogen prices could conceivably reach $1.00/lb N early next year. So, the question becomes what management strategies ruminant livestock producers could use to manage soil fertility as fertilizer markets continue to experience volatility.
Management Strategies: No “Silver Bullets”
Figure 2. Few nutrients are removed from grazing systems. Nutrients enter grazing systems via feed, fertilizer, and nitrogen fixation in legumes and are recycled by grazing and deposition of dung and urine and decomposition of plant residue and senesced roots (Illustration by Chris Teutsch, UKY).
We wish we had a miracle cure for high fertilizer prices, but we don’t. And we would caution you to closely scrutinize claims from retailers of products that are offering you something that sounds too good to be true. One competitive advantage that well managed grazing systems have is that nutrient removal is very low and with good grazing management strong nutrient cycles can be developed (Figure 2). Below you will find some strategies that can be implemented to help you get through the current period of high fertilizer prices.
Soil test pastures and hay fields. You are probably saying to yourself why in the world would I even bother soil testing when fertilizer prices are so high. It is impossible to manage something without data. A soil test allows you to target fertilizer applications to fields that have the potential to respond. If the P or K soil test level for a given nutrient is in the low range, then the probability of a yield response is high (Table 1). If the P or K soil test level is in the medium or high range, the probability of a yield response diminishes. So, our best advice at this time is that if your soil test value is a SOLID MEDIUM, do NOT apply that P or K fertilizer until prices moderate.
Monitor soil test levels in hayfields closely. Since hay removes much higher quantities of nutrients than grazing, it is important to closely track nutrient levels and apply P or K fertilizer when soil test values drop below the MEDIUM range. This will prevent nutrient mining and yield decline.
Figure 3. Soil testing is an important tool for managing soil fertility in pastures, especially when fertilizer prices are high (Photo by Chris Teutsch, UKY).
Apply lime according to soil test. Soil acidity or alkalinity can have a profound impact on soil nutrient availability to forage plants (Figure 3). Maintaining soil pH between 6.0 and 7.0 results in the greatest availability of macro- and secondary-nutrients such as nitrogen, phosphorus, potassium, magnesium, and sulfur. In contrast to fertilizer prices, lime costs have remained about the same. If your soil test indicates that you need lime, it will likely be the best buy you can make at the current time.
Capitalize on nutrients in hay. Every ton of hay contains approximately 50 lb N, 15 lb P2O5, and 50 lb K2O. The current value of the nutrients in one ton of hay is approximately $50. How we manage hay feeding will determine the actual value of these nutrients. If we feed hay in one paddock near the barn, then the value of these nutrients will be low because they will be concentrated in one small area. In contrast, if we move feeding points and feed the hay on pastures with lower soil test values, then the value of the nutrients in hay will be higher.
Implement rotational stocking. This doesn’t sound like much of a nutrient management strategy, does it? In large continuously stocked pastures, animals will consume nutrients in the form of forage and concentrate them around shade and water sources in the form of dung and urine. One way to improve nutrient distribution in pastures is to subdivide and implement rotational grazing. Confining livestock to smaller areas for short periods of time significantly improves dung and urine distribution.
Replace commercial nitrogen by overseeding clover into pastures. Legumes fix nitrogen from the air to a plant available form via symbiotic nitrogen fixation, improve forage quality and animal performance, and dilute the toxic effects of the endophyte found in tall fescue. Red and white clover are estimated to fix between 50 and 120 lb N per acre per year. This fixed nitrogen is indirectly shared with legumes through grazing and the associated deposition of dung and urine, through death and decomposition of above and below ground plant parts, and the senescence of root nodules.
Frost seed clover in February. The simplest and most cost-effective way to introduce clover into pastures is by broadcasting 6-8 lb of red clover/A and 1-2 lb of ladino clover/A onto closely grazed pastures in February and allowing the freezing and thawing cycles to incorporate the seed. Allow animals to remain on these pastures until the new clover seedlings have become tall enough to be grazed off. At his point, remove animals and allow the seedling to reach a height of 8-10”. At this point, these pastures can be incorporated back into the rotation.
Determining nitrogen fertilizer needs. There are no good soil tests for N, so use university rate recommendations. Most rate recommendations are a ‘range’, so consider an application rate at the lower end of the range when fertilizer N prices are high. Consider your personal experience with N response in your pastures and hayfields. Well managed pastures that have a strong legume component and are rotational stocked can have strong nitrogen cycle. This will tend to make them less responsive to nitrogen fertilizer. Remember, more N drives more grass growth, BUT it is only a good investment if the additional forage will be utilized!
Figure 4. Impact of soil pH on availability of nutrients to plants. The wider the band, the more plant available a given nutrient is. Maintaining soil pH between 6.0 and 7.0 optimizes the availability of essential plant nutrients (Figure from the NSW Department of Primary Industries).
Take Home Points
Although there is no “silver bullet” for high fertilizer prices, some key management strategies will help you weather these high prices in the short-term and develop grazing systems that are less dependent on commercial fertilizer inputs in the long-term.
- Soil test pastures to provide baseline data for short- and long-term fertilizer management.
- Do NOT apply P and K fertilizer to pastures testing MEDIUM until fertilizer prices moderate.
- Apply needed lime to pastures according to soil test to make nutrients in the soil more available to forage plants.
- Closely monitor soil test levels in hayfields to prevent nutrient mining and yield decline.
- Feed hay on pastures with low soil test values.
- Move hay feeding points around the pasture to improve nutrient distribution.
- Implement rotational stocking to improve dung and urine distribution in pastures.
- Frost seed clover into pastures to improve forage quality, help with tall fescue toxicosis, and fix atmospheric nitrogen into a plant available form.
- Apply fertilizer nitrogen at the lower end of the recommended rate range, knowing that you will use resulting grass growth.