Pasture fertilization is a significant expense. Photo Credit: Doug Mayo
One area of management that often comes up in discussions with producers managing smaller herds is pasture fertilization. There are several aspects that can be confusing. The first questions are, “Should I fertilize?” and, “Is it worth the money?” The next question is, “How much fertilizer do I need?” And generally, the final question, “What should I ask my supplier for?” When you ask these questions, however, be ready for the return question, “Have you taken a soil test?”
In declining cattle markets, the question of “Should I fertilize?” is a subject of much debate. You don’t have to fertilize bahiagrass pastures, but there are consequences if you don’t adjust your stocking rate. If you don’t fertilize or reduce your stocking rate, there may not be enough grass in the fall transition, and eventually there will be issues from thinning stands and weed encroachment.
Basic soil management for forages, or any crop, requires that the soil be maintained in the optimal pH range for the specific target crop to ensure productivity and persistence. For tropical forages, such as Bahiagrass, Bermudagrass, and Limpograss the optimal pH range is 5.0-5.5. Outside of the optimal pH range, soil nutrients are less available to the plant. This is one of the key reasons that periodic soil testing is recommended for pastures. Lime or dolomite are utilized interchangeably to raise the soil pH. Liming pastures is relatively inexpensive because it is generally only required every 2-4 years.
So, should you fertilize? If the soil pH falls below the optimal range, the answer is yes. For $40 per ton, the return on investment in lime or dolomite is high. If you do nothing else for your pastures this year, make sure to lime the Bahia and Bermuda fields that fall below 5.5, or limpograss fields below 5.0. If you can’t remember how long ago you had your soil tested, send in a soil sample, and and at least find out the pH status of your pastures.
Soil tests don’t provide the amount of nitrogen in the soil, because those amounts are constantly changing. Nitrogen (N), and to some degree potassium (K), move with water in the soil profile. With each heavy rain, some nitrogen is flushed down through the soil profile, away from the root zone of plants. There are 16 essential elements for plant growth and reproduction, but nitrogen is the key element that plants require for growth. In other words, “Nitrogen is the gas that makes grass grow!” The chart below is the summary of a classic six-year study conducted a the UF Beef Research Unit from 1966-71 by W.G. Blue, UF Soil Chemist: Role of Pensacola Bahiagrass Stolon-Root Systems in Leon Fine Sand.
What is interesting from this study is that the season-long forage yield more than doubled when 100 lbs.N/acre was applied as compared to no added N. However, with each increase beyond 100 lbs.N/acre, the return on investment diminished. It is important to note that all of the plots were fertilized equally with phosphorous and potassium, at a soil pH of 6.0, so the yield in the 0 N, or control plots, were only limited by the lack of nitrogen. These research plots received split applications of fertilizer, so none of these treatments were a single N application. This classic study shows what numerous others have shown since then, that nitrogen fertilization generates a significant boost to bahiagrass production.
Urea fertilizer (46% N) is currently priced at an average of $414/ton, which equates to 45¢/lb. of elemental N. The reported 119% season-long increase in forage production per acre would require a $45 investment in nitrogen fertilizer today. When you add the $7/acre cost to spread the fertilizer, and you have a stocking rate of 2 acres per cow-calf pair, the total cost is $104 per pair ($52/acre). So, based on the data from this classic study, a $104 investment provided 3.4 tons more feed per pair over the entire growing season for a unit cost of $31/ton. At the end of April, good quality Bermudagrass hay was selling for an average of $90/ton, and whole cottonseed $158/ton, so this is considerably cheaper than purchase feeds. This is also feed that requires limited labor to provide, with minimal waste, under typical weather conditions. In addition, fertilized grass provides more protein than unfertilized grass, so animal performance (gain/acre) would also be boosted, as compared to unfertilized pastures.
If you don’t have the funds to invest $52/acre for all of your pasture acreage, then consider applying only of 50 lbs.N/acre in the spring. You don’t have to fertilize every acre either. Invest in your most productive pastures first, and then rotate to other pastures in future years. Fertilizer is an expensive purchase, and when cattle prices are falling, every purchasing decision has to be scrutinized. The bottom line is that nitrogen fertilizer is really an investment in producing feed for your herd that they harvest for themselves. Conversely, if you make the decision to eliminate nitrogen fertilization, your pasture will produce less feed, so you also need to reduce the number of cattle your pastures are expected to feed.
P & K Fertilization
The next question is how much P & K fertilizer do you need for your bahiagrass pastures? In general, grasses need N-P-K fertilizer in a 4-1-2 ratio. So, you would not want to use 13-13-13 or 10-10-10 for grass pastures, but instead something like a mix of 16-4-8 or 20-5-10. The better option, however, is to send in a soil and tissue sample to get a lab test report that provides specific recommendations for the rate of lime, phosphorous (P) and potassium (K) fertilization on a per acre basis. The N fertilization level is a decision the manager has to make. The University of Florida’s soil test-based fertilizer recommendations provide options for three levels of nitrogen fertilization. The recommendations for P and K will be different based on the nitrogen fertilization level you select.
The final question I normally get is, “What should I order from my farm supply dealer?” This does sometimes get confusing, because recommendations are made in pounds of nutrients per acre, not the total pounds of fertilizer. Urea, for example, is only 46% elemental nitrogen, so it takes 109 pounds of urea to provide 50 lbs.N/acre. Ammonium nitrate is 34% N, so it takes 147 pounds to reach the 50 lbs.N/acre target. The same is true for the various sources used for P and K. Farm supply dealers handle a variety of products from different sources with varied mineral make up. There is no standard recipe. Take your soil test recommendations with you, so your dealer can help you do the calculations as to the total pounds of the blended fertilizer you want applied.
If you have questions about pasture fertilization, soil and tissue testing, or the soil test report recommendations, contact your local UF/IFAS County Extension Agent. Make sure you clearly understand the options, before making an investment of this magnitude.
Commercial cow grazing at the North Florida Research and Education Center, Marianna. Credit: Doug Mayo
Marcelo Wallau – UF/IFAS Forages Extension Specialist, Caitlin Bainum – UF Agronomy Department MS Student and Marion Co. Agriculture & Natural Resources Extension Agent, and Liliane Severino da Silva – UF Agronomy Department PhD Student
It is never too early to start planning. As summer approaches, our main forage growing season in Florida, there are a few steps to be taken to ensure you have a great season and get the most out of it productively! Stuth et al. (1991) divided resource planning for grazing lands into long-, medium- and short-term plans. Long-term is the strategic planning, defining objectives, goals, focus animal category, markets, policies, financing and land improvement investments. The medium-term is the tactical planning, where we define the forage budget, needs and supply of forage, stock adjustment, nutritional balance and health management. Last, is the day-to-day, the short-term, the operational planning. At this point, we assess forage supply, identify needs for restocking or destocking, or supplemental feed for nutritional mediation, and health treatment. Flexibility is the key word for this level, so we can easily correct eventual problems. Here, we will focus on medium-term planning that can help you get the most out of this next grazing season.
First, evaluate your pasture conditions – Think about the history of your pasture, how productive it was last year, the challenges faced, how was the management in terms of grazing, fertilization, weed control, etc. If you encountered problems last year, more likely they will repeat this year, unless you mitigate them. Last year was quite challenging for most parts of Florida, starting with a drought over spring and summer, then with excessive water leading to flooded pastures for the remaining of summer and into early fall. Those disturbances could have imposed significant stress to your pastures, leached nutrients and even reduced persistence by reducing the amount of energy reserves for the plants. All of this could mean that you are in for a late start this year. Overgrazed pastures will have a similar effect, with reserves depleted, they will take longer to start greening the following spring. This can result in higher weed pressure and further delay grazing. Thus, soil test and check what nutrients are missing, and plan your applications for early in the season, when plants are starting to grow, so they can use the nutrients, especially nitrogen, better. Many problems on pasture persistence, disease or insect susceptibility are linked to deficiency in potassium (K), for example. Talking about weed pressure, was there any weed problem last year that could be addressed now? For some weeds, hitting them in the beginning of the season can result in better control and less expense. Scout for weeds, ID them, and consult your extension agent on which is the best product and strategy that suits your needs.
1 – Calculate your forage budget
Like your bank account, you need to have a balance between resources available and demands. If you need more forage than you can produce, then you are in the red, which will cost you money in importing supplies. So, first, calculate your forage supply to learn your carrying capacity. Create an excel spreadsheet, map your areas, evaluate the conditions of your pasture and calculate how much forage you can produce. Figure 1 provides some general values for daily herbage accumulation rates (lb of dry mater [DM] per acre per day) that some of the most common species in Florida produce. Those values change according to fertilization rate, water availability and grazing management, but are a good reference for starting a forage budget. Remember to always leave 1200 lb of DM/acre as stubble, in other words, use only 50 to 60% of the accumulation rate, to ensure that you have enough forage for your cattle as well as the plant’s demands for surviving. Another way to look at it is to always offer 2 to 3 times more than the animal needs to consume per day.
The second step is to determine your demand both in terms of quantity and quality of forage needed. This way you can adjust your management practices, use techniques to enhance the nutritive value of forages produced, and finally, see if there is need to reduce or expand your herd accordingly. Take into consideration that your cattle need to eat around 2.7% of their body weight in dry matter per day (between 2 and 3%, depending on forage quality and physiological stage), and that dry cows need significantly lower quality forage (8% crude protein) as compared to lactating cows and growing animals (12 to 16%).
The third step is to calculate the balance between supply and demand for forages. In many cases, demand for forage exceeds supply, requiring destocking, or finding extra sources of feed in the form of supplement, hay, or extra pasture. If you have extra supply, then there could be an opportunity to retain or purchase more animals, or harvest for hay or haylage. Nitrogen fertilization can increase the quantity and quality of forage produced. But remember, no management practice for the pasture (fertilization, rotational grazing, etc) will overcome overgrazing.
Figure 1. Herbage accumulation rate (lb of dry matter [DM]/acre.day) for bahiagrass and limpograss (Gainesville, FL) and bermudagrass (Marianna, FL) (data courtesy of Drs. José Dubuex and Lynn Sollenberger).
2 – Plan your pasture utilization strategically
Think about your farm as a mosaic of different soil patches and pasture types, and plan forage management to match your property to optimize pasture use along this mosaic over the year. Some forages, like limpograss, for example, are more adapted to lower areas susceptible to periodic flooding. Those areas are also generally wetter in the spring. This means that limpograss could be an early starter and also a late player, with possibility for stockpiling forage for fall use. Protein, however, is very low, so factor in using this with mature cows and the need for protein supplementation. Bermudagrass has production more concentrated in the summer months, and is an excellent forage for growing animals, like weaned calves and replacement heifers, for example. For summer pastures overseeded with cool-season forages, remember to reduce competition (graze down the cool-season forage) towards the end of the spring, so you can reduce competition for your bahiagrass or bermudagrass. Also think about the areas that could be used for cool-season forages next fall, and manage them accordingly. When you start thinking about the farm as a whole, with different forage species and management strategies, it becomes easier to fit the different pieces together and make a system.
3 – Keep it simple and flexible
Simple strategies can solve many problems! Before implementing more advanced management techniques, do the simple steps first. Again, no management practice can overcome excessive grazing, and any applied management will have the response limited by the lack of forage. So, start with the forage budget, then think about fertilizing your pastures, supplementing your cattle, and then move on to more complex management systems. And, always keep it flexible, leave room for error and unexpected events. Expecting too much or working close to the limit of forage availability can be risky, any change in weather or market prices that requires you to retain cattle longer can have some serious implications in your system. Different than cattle, pastures don’t have compensatory gain, and mismanagement can set you back half a year or more.
4 – Assess, evaluate, and re-assess
You can only improve what you can measure, so take notes, measure your pasture productivity and animal performance, record and evaluate that in comparison to your goals. Those notes will help you for next year’s planning. Make sure your goals are in accordance to your production capacity.
Reference: Stuth, J.W.J. R. Conner, and R. K. Heitschmidt. 1991. The decision- making environment and planning paradigm. In Heitschmidt and Stuth, eds. Grazing management. 201-24.
Cows gathered around a hay feeder in Washington County. This has been an all too common scene this winter while cattle and cattlemen alike wait on cool-season forages, which have gotten off to a slow and rocky start this year. Photo credit: Mark Mauldin
Cool-season annuals (ryegrass, small grains, clovers, etc.) are a vital part of our forage systems here in Northwest Florida and throughout the Southeast. Generally speaking, cool-season annuals are the highest quality forage we are able to produce. The significance of these forages is evidenced by the fact that many producers time their calving seasons so that the herd’s period of peak nutritional demand coincides with the peak production period of cool-season forages.
A tough season for cool-season forages
The recommended fall planting window (October 1 – November 15) was abnormally dry, forcing most producers to plant later than recommended. Later plantings force seedlings to emerge to colder temperatures (soil and air) and shorter days, with fewer hours of sunlight each day. Both of these factors cause forages to get off to very slow starts. Even ambitious producers that planted early, before the drought set in, faced significant challenges. Worst-case scenario, early plantings germinated and then died during the prolonged dry period. Best-case scenario, plant growth was so limited by dry conditions that expected plant performance advantages associated with timely planting have only recently become noticeable.
To further compound the situation, when the rain finally came, cold conditions (brutally cold by Florida standards) came with it. Keep in mind, the forages in question are referred to as “cool-season” not “cold-season.” While we generally are not concerned about Florida winter temperatures killing these plants, truly cold conditions can damage them, and will certainly prevent them from peak performance. In other words, forages that got off to a slow start from limited moisture were further delayed by the extended cold weather this year.
As growing conditions have improved in recent weeks the significance of planting date has become more evident in this Washington County ryegrass. These images were taken on 2/15/18, all within 10 minutes and 100 yds. of each other. None of these fields have been grazed. Photo credit : Mark Mauldin
Finally, growing conditions have improved considerably recently. Moisture has been adequate, even excessive this past week, and temperatures have warmed considerably. These factors combined with the lengthening days have really kicked forages into gear.
Key Forage Management Considerations
- Be patient; don’t graze your forages too soon. Let forages accumulate adequate leaf area/height before grazing. Ryegrass and small grains need have 8 to 12 inches of growth before grazing.
- Don’t graze forages too close. Removing all or nearly all leaf area greatly reduces the plants’ ability to regrow after grazing. The more leaf area left the faster the plants will regrow. The concept of “Take Half, Leave Half” is good to keep in mind when determining grazing height. Never graze ryegrass or small grains shorter than 3 inches, if regrowth if desired.
- Maximize forage utilization by implementing some form of controlled grazing. When cattle are allowed continuous access to forages, they will graze preferentially and trample more forage. When access is restricted by space, time, or both, cattle will graze more efficiently and forage utilization will increase.
- Allocate forages strategically. Cool-season annuals have a very high nutritional value. When they are in short supply, reserve them for animals that have the highest nutritional demands; lactating females and/or growing animals. This practice can greatly increase the value cool-season annuals bring to your operation, but it requires the ability and willingness to sort and manage cattle in different groups.
- Don’t forget about soil fertility. Maintaining adequate soil fertility will bolster plant performance. In many cases the performance of under fertilized forages will not be sufficient to warrant the initial establishment cost. Additionally, stressors, like nutrient deficiencies, can prompt annuals to forgo vegetative growth for reproductive growth, and set seed earlier than they otherwise would have.
- Maximize the growing season of annual forages. When annual plants make seed they stop vegetative growth. If conditions remain favorable and forages are able to “get ahead of the cows” be prepared to adjust stocking rates and/or controlled grazing practices to delay seed production for as long as possible, by allowing cattle to keep forages “toped-off”. As we get later into the spring, consider stockpiling forages planted on prepared ground and grazing over-seeded forages harder to prevent damage to the underlying perennial forages as they break dormancy.
[important]I understand. You’re tired of feeding so much hay, you’re past ready to turn out onto some grazing, your cows are tearing through the fence to get to something green, but that doesn’t mean you can throw open the gate and walk away. Years with poor growing conditions call for better management than years when conditions are optimal. The financial investment associated with establishing forages is the same regardless of the production; do what you can to maximize your return on investment.[/important]
Distribution of cool-season forage growth during a “normal” year. We are just entering the major growth period for the majority of our cool-season forages. Don’t give up on management; take full advantage of the remainder of the growing season. Image from: Forage Systems for Stocker Cattle, UGA Extension Bulletin 1392.
We don’t know how long growing conditions will remain favorable. Take steps now to ensure that your cool-season forages are able to bring as much value to your operation as possible. Even if it seems like your forages are really under-performing this year, don’t give up on management. Well managed cool-season annuals still have several months of growth left. There is still time to produce a substantial amount of nutrition for your herd. The considerations listed above are general guidelines. Every operation has different challenges and opportunities. Consult with your county’s UF/IFAS Agriculture Agent for assistance implementing strategies that can help you get the most out of your cool-season forages, this year, and in the future.
Cheryl Mackowiak, UF/IFAS NFREC Soils Specialist
As producers near the end of cover crop and cool-season forage planting in the Southeastern U.S., it is time to focus on fertilization. Depending upon your state, extension professionals have establish guidelines for how much and when to apply nitrogen (N), phosphorus (P), and potassium (K) fertilizers to meet crop demands. For example, annual ryegrass and small grains (i.e., wheat, oat, rye, triticale) planted on tilled land often benefit from split N rates such as 30 lbs N/acre at or near planting and another 40 to 50 lbs N/acre after establishment. Overseeded pastures may get by with an initial 30 lbs N/acre, but often 50 lbs N/acre is applied once the cool-season grass has emerged with another 50 lbs N/ac applied after repeated grazing to help support regrowth in spring, when winter forage is the most productive. In comparison, P and K applications are based upon soil sampling and your soil report recommendations. These nutrients are typically applied only once in the fall (if needed), and combined with your first N application.
Frequently, a call comes in that a farmer’s winter grass forage does not seem to be responding to N fertilizer. They have met or exceeded the N fertilizer recommendations and yet, the plants remain faded looking and stunted. The first question I ask: “How much sulfur (S) was applied?” Sulfur deficiency can often be mistaken for N deficiency in both, summer and winter grasses. We typically see more problems in winter grasses, because of where the grasses are planted and the previous season land-use. If none of your N fertilizer was applied as ammonium sulfate, or your K fertilizer did not contain potassium sulfate, SolPoMag, or a similar sulfate fertilizer, your grass may be suffering from S deficiency. The good news is that many grass species respond quickly to S fertilization, and an application rate as low as 10 lbs S/acre is often all that is required for recovery. An application of 10 to 20 lbs S/acre will hardly be noticed in your fertilizer bill.
Fig. 1. Nitrogen deficiency due to a faulty fertilizer applicator. Areas of stunted growth are relatively large and plants in the deficient areas appear more uniform than under S deficiency. Credit: Cheryl Mackowiak
Fig. 2. Mechanically induced N deficiency (strips of ample growth alternating with growth suppression). Credit: Cheryl Mackowiak
Both, N and S nutrient deficiencies will result in stunted growth, and a yellow color. However, if it is N deficiency, it is more typical that the field canopy will appear uniformly yellow over large areas, or you will observe straight line streaks where the fertilizer truck may have overlapped with the previous pass (Figs. 1 and 2). Upon closer inspection, the lower (older) leaves of N deficient plants will be lighter green or even yellow (Fig. 3).
Fig. 3. Close-up of N deficiency, with older (lower) leaves lighter or sometimes yellow, compared to more recently emerged leaves. Credit: Cheryl Mackowiak
With Sulfur (S) deficiency, the field will have a splotchy or mottled appearance, and sometimes the affected plants are intermixed with healthy looking plants (Fig. 4). Upon closer inspection, the newer leaves on individual plants may be lighter green than the older, or more basal leaves (Fig. 5).
Fig. 4. A small grains study site displaying classic S deficiency symptoms. Credit: Cheryl Mackowiak
Fig. 5. Individually affected plants will appear uniformly lighter green, or younger leaves may be lighter colored than older leaves. A visually healthy plant may grow adjacent to an impacted plant. Credit: Cheryl Mackowiak
Conditions that may lead to S deficiencies include, the lack of at least 10 lbs S, in sulfate form, as part of your fertilizer blend (elemental S will not provide a quick enough response), planting on row crop land, or planting on new land that had been forest or pine plantation (often locations for wildlife food plots). Well-managed pastures are less likely to suffer from S deficiencies, since livestock excreta contributes S to the soil. Not all labs analyze for soil S, so the safe bet is to include a small amount (10 to 20 lbs S/acre) of sulfate S in your fertilizer blend. Check the fertilizer label if you purchase bags, or make the request when you hire custom fertilizer spreading. If you have to apply the S fertilizer yourself (small areas), you can purchase SulPoMag, potassium sulfate, calcium sulfate (i.e., gypsum), or magnesium sulfate at many feed and seed stores. Remember, cool-season legumes (clovers, vetch, peas, etc) benefit from 20 lbs S/acre fertilization, as well!
For more information related to this subject, use the following UF/IFAS publication links:
Jose Dubeux, Liza Garcia, David Jaramillo, Erick Santos, UF/IFAS North Florida Research and Education Center
You might not be familiar with the term “Ecosystem Services,” but putting it simply, these are the benefits obtained from ecosystems (interactions between living organisms in a particular environment). These services benefit both people and the environment. Ecosystem services (ES) provided by grasslands include not only products such as beef and milk (provisioning ES), but also biological nitrogen fixation (N2-fixation) and nutrient cycling (supporting ES), carbon sequestration and greenhouse gas mitigation, water capture and purification, shade, windbreaks, habitat for pollinators and wildlife (regulating ES), and finally cultural (e.g. habitat for wildlife), and aesthetic ES.
Grassland managers are providing all these benefits to society, and they ought to receive compensation for that. Payment mechanisms might work in various ways, including tax breaks, direct monetary compensation, and cost-share programs. The first step, however, is to quantify and assign a monetary value to these ES. Researchers at the University of Florida are trying to accomplish this through a USDA-funded project currently being conducted in Marianna and Gainesville, Florida.
Figure 1. Honeybee on white clover flower in Citra, FL (left) and on rhizoma peanut (perennial peanut) flower in Marianna, FL (right). Photo credit: Jose Dubeux
When legumes are integrated into grass pastures, the potential to provide additional ES is increased. Legumes are able to fix atmospheric-N2 by associating with soil bacteria (reducing N-fertilizer input as a result), provide flowers for pollinators (Figure 1 above), and improve forage quality. Preliminary data indicate that 12 different bee species benefit from grass-legume pastures in Marianna. Adding legumes might also increase primary productivity in low-input systems, with grass-legume mixtures outperforming monocultures, enhancing nutrient cycling and carbon sequestration.
Figure 2. Typical in vitro organic matter digestibility (IVOMD) and crude protein (CP) of bahiagrass and rhizoma peanut.
Forage legumes are often more digestible and have greater crude protein than grasses (Figure 2 above). This often results in greater livestock performance when grazing on grass-legume pastures as opposed to grass monocultures (Figure 3 below).
Figure 3. Livestock performance (average daily gain – ADG) on unfertilized Bahiagrass, N-fertilized Bahiagrass (100 lbs. N/acre), and Bahiagrass-rhizoma peanut pastures (Dubeux et al., 2016).
Currently researchers at North Florida Research and Education Center in Marianna are assessing the ES provided by N-fertilized grasses and grass-legume systems . Grass-legume systems of Bahiagrass-rhizoma peanut pastures in the summer are overseeded with cool-season grasses (rye and oat) and clovers (crimson, red, and ball) over the winter (Figure 4 below).
Figure 4. Grass-legume pastures in Marianna, FL. On the left, warm-season mixture with Argentine bahiagrass and Ecoturf rhizoma peanut; on the right, cool-season mixture with cool-season grasses and clovers. Photo credit: Jose Dubeux
Preliminary results indicate similar livestock gains for grass-legume systems fertilized only with only 30 lbs. of nitrogen per acre, compared to grass only systems fertilized with 200 lbs. N/acre (Table 1).
Other ecosystem services are currently being assessed in the same project. A multidisciplinary team is working on different aspects of grassland ecosystems, including soil, vegetation, livestock, bees, water quality, and economics. At the end of the project, the hope is to provide comprehensive information on all these aspects.
Take Home Message
Grasslands produce far more than beef and milk. They provide additional ecosystem services (ES) that benefit society. Integrating forage legumes into grasslands enhances the capacity to provide these benefits. In Marianna, researchers are assessing an array of ES provided by N-fertilized grass and also by grass-legume pastures. Preliminary results indicate the possibility to produce similar livestock gains in grass-legume pastures using only 15% of the N-fertilization typically used in grass monocultures. Other ES such as presence of bees, carbon sequestration, and mitigation of greenhouse gases are also being assessed. The goal is to quantify the economic value for these different ES provided by grazing systems. Public policies could then be established to provide financial incentives to livestock producers through conservation programs. Hopefully these incentives would at least offset some of the cost of establishment for grass-legume systems on farms. With ES benefits more clearly defined, this could become a win-win situation, both for society and for the land owner.
Dubeux, J.C.B., Jr., L. Garcia, N. DiLorenzo, C. Prevatt, A. Blount, C. Mackowiak, E. Santos, D. Jaramillo, M. Ruiz-Moreno. 2016. Reduce your N fertilizer cost and maintain cattle productivity by planting forage legumes. The Florida Cattlemen and Livestock Journal, December 2016, v.81, n.3, p.94-97.
ARS agronomist Haile Tewolde inspects cotton fertilized with chicken litter near Coffeeville, Mississippi. Photo by John Brooks.
Dennis O’Brien, USDA ARS Office of Communications
A USDA Agricultural Research Service (ARS) agronomist in Mississippi has found a way to help cotton growers in the Southeast maximize profits when they use poultry litter as fertilizer.
The practice makes sense. Poultry litter (chicken waste, spilled feed, excess feathers, and other poultry-house materials) contains nitrogen and phosphorus, both important crop nutrients. Applying it to the soil recycles tons of litter generated annually by poultry operations throughout the United States, says Haile Tewolde, an ARS agronomist in the Genetics and Sustainable Agriculture Research Unit.
More farmers are using poultry litter these days, but some apply more than they need. The excess nitrogen and phosphorus can dissolve in storm runoff and pollute surface and ground waters. Farmers who raise cotton and other row crops wanted guidance on how best to use it.
Previous studies have determined profitable rates for commercial fertilizers, but there is little information about how much poultry litter cotton growers should use to maximize profits. “We thought the economic implications for growers were worth exploring,” Tewolde says.
Cotton boll ready for harvest. Photo by Haile Tewolde.
Tewolde and his colleagues used a commercial fertilizer spreader to apply poultry litter to cotton at seven different rates on two farms. They measured cotton lint yields for three years at one farm and five years at the other. For comparison, they also measured yields where they applied standard rates of synthetic fertilizer. They also factored in litter costs and cotton’s market price to determine optimal rates for profitability.
The researchers found that the most profitable rate differed from rates that produced the highest yields, because of the current low market value of cotton. Maximum yields were achieved with 9,000 to 12,000 pounds of litter per acre, but profits were highest with only 7,000 pounds per acre. They could achieve slightly higher yields only by adding considerably more litter. “If cotton prices were to rise significantly, they could reach a point where it would pay to apply more litter. But cotton prices have stayed low in recent years,” Tewolde said.
The results give cotton growers specific recommendations that should help them avoid applying more litter than they need. They also highlight poultry litter’s capabilities as a fertilizer. Growers who use poultry litter were unsure if they could meet their nitrogen targets with poultry litter alone. The results show that they can, and they spell out how to provide the right amount of nitrogen and no more.