Fertility

Pasture Fertilization

Illinois

Introduction

Pastures respond to a fertilization program like any other crop. However, in designing a pasture fertilization program, the producer must consider the productivity of the grazing animals, the plant species present, and the management level and goals for the pasture. Fertilizing pastures is different than fertilizing for hay. Research data and farmer experience has shown that pasture productivity can be increased two to three times with a well-planned and managed fertilization program.

Starting Point

A current and accurate soil test is the best guide in designing a pasture fertilization program. Collect one composite sample per 2 ½ acres in late summer or early fall. Ideally, each paddock should be sampled separately. Slope and aspect should be sampled separately. Avoid sampling where livestock tend to “camp” (near water and shade).

Soil samples should be analyzed for pH, available phosphorus (P1), and potassium.

For existing pastures, sample to a 7-inch depth and collect a few samples (maybe 20% of total), in a separate container, to a 2-inch depth for pH only. Where lime is needed, adjust the rate to account for surface application (lime rate dependent upon the volume of soil neutralized). Some testing laboratories make lime recommendations based on sampling depth.

When planning to establish a new pasture in a prepared seedbed, plan ahead. Sample 6 months to a year before seeding, to a 7-inch depth and incorporate needed lime with tillage at least 6 months before seeding.

Species and pH

Pasture grasses can grow over a wider range of pH than legumes. As a general guide, soil pH for cool-season grass pastures should be 6.0 to 7.0 and 6.5 to 7.0 for legume pastures. A minimum pH of 6.5 is suggested for legume/cool-season grass mixtures.

Legumes "make" N

Legumes “fix” atmospheric nitrogen and make it available for plant growth. If legumes comprise 30 percent or more of the sward, do not apply nitrogen fertilizer since an adequate amount will be contributed through fixation. If the legume portion is less than 30 percent, grass will probably respond to nitrogen fertilizer.

Studies have indicated that a legume-cool season grass mixture produces more than a nitrogen-fertilized grass pasture.

Legumes should be properly inoculated when seeded to assure good
nodulation.

Impact of P and K

Phosphorus (P) and potassium (K) are essential nutrients for plant production. Once the soil is corrected to optimal soil test levels (P1 of 40 to 50 pounds per acre and K of 260 to 300 pounds per acre) for these nutrients, monitor their status by soil testing every 4 years. Optimal levels will vary by soil type, area of the state, and to a certain extent by the species grown. Once these optimal levels have been reached, additional P and K fertilizer is not considered economical nor does it provide for consistent yield responses.

Grass Needs N

Nitrogen is essential for the formation of protein and thus stimulates production. Nitrogen fertilizer should be considered for a grass dominant pasture. Research indicates that the first 30 to 50 pounds per acre of nitrogen are used most efficiently and that split applications of this amount generally maximize yield.

Grass pastures will respond quickly to nitrogen-make sure you can utilize the forage produced.

The first application should be made in late summer to stimulate growth for fall production (for those utilizing deferred grazing or stockpiling, an early August application is suggested). The second application should be made in early June when the spring flush of grass growth is over. Since early season growth is generally excessive, an early spring application is not suggested unless the first harvest can be efficiently grazed or will be harvested as hay or silage. Nitrogen application early in the season can make the grazing management of the spring flush more difficult.

Source of nitrogen is important for summer application. Urea or UAN solutions are easily lost if a 0.5-inch rain does not occur shortly after application. Ammonium and nitrate forms of nitrogen are non-volatile and can be applied without significant loss.

Nutrient Cycling

Sixty to 80 percent of the P and K removed by grazing is returned or recycled on the pasture in the form of manure and urine. Grazing animals also recycle a significant amount of N from consumed pasture forage. Nitrogen in urine is quickly converted to available ammonium and nitrate. Nitrogen in dung is slowly released and utilized by surrounding grass.

Manure distribution is greatly affected by grazing management. Manure and urine distribution is more uniform on rotationally grazed pastures since animals spend less time in any one site and forages are grazed more evenly. A high stocking density and short grazing period will also improve the uniformity of manure distribution.

Manure as Fertilizer

In addition to the nutrients distributed during grazing, some producers spread manure on pastures. This is an acceptable practice but needs to be done with caution. Manure should be applied shortly after a grazing period. It should be applied first to grass pastures. Manure can make the forage less palatable. There will be volatilization loss of nitrogen from surface applied manure. One should monitor P and K soil test levels. To minimize P and K runoff, do not apply to sloping, frozen ground.

Plant Analysis

Tissue analysis can be used to diagnose forage production problems (especially status of micronutrients), to check the nutritional status of the forage, and to fine-tune fertility and grazing management. Tissue analysis should be used with, not instead of, soil test results.

For More Details

Additional information is found in the Illinois Agronomy Handbook available at Extension offices.

Summary

Fertilization, along with well-managed livestock and forage, is key to an efficient pasture program. Pasture fertilization management is a continuous process.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audio tape, etc.) should contact USDA’s TARGET Center at 202-720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, 1400 Independence Avenue, SW, Washington, DC 20250-9410 or call (202) 720-5964 (voice and TDD). USDA is an equal opportunity provider and employer.”

Fertility

Soil Sampling and Testing

Illinois

Introduction

This fact sheet is designed to complement “Pasture Fertilization” dated November 2000. Soil sampling and soil testing is the first step in planning a pasture fertilization program. This fact sheet provides guidelines to help maximize the value from soil samples.

Depth of Sampling

Sampling depth is very important to avoid over-predicting (result of shallow sampling) and under-predicting (result of sampling too deep). Seven inches is the suggested sampling depth for both established pastures and new plantings. Sample to this depth for phosphorus (P) and potassium (K) recommendations, and for soil pH in new plantings. In an established pasture, also collect a few samples (maybe 20 percent of the total) to a depth of two inches for pH analysis.

Number of Samples

The number of samples taken from a pasture is a compromise between what should be done (information) and what can be done (cost). It is suggested to sample at the rate of one composite sample per 2½ acres, no more than one composite sample for every five acres. A composite sample is comprised of at least five sub-samples, as shown below. A sub-sample would be taken at each spot marked by an “X”. Crumble and mix the sub-samples together, remove one pint and this represents one sample. Record where samples were taken in the pasture.

Where to Sample

Each paddock, different topography (hilltop, bottom ground, etc.), and aspect (direction of slope) should be sampled separately. Avoid sampling within 100 to 150 feet of shade trees, watering points, and other areas where livestock congregate.

How to Sample

A one-inch soil probe is the preferred tool for taking soil samples, but an auger or spade can also be used. See below figure.

Be sure to sample to the correct depth (see above) and collect all of the sample (don’t let soil drop out from the top portion of the core).

Number of Samples

When to Sample Pastures should be sampled every three to four years. Late summer and fall are the best seasons for sampling to avoid the cyclic nature of nutrients, especially potassium. Always collect subsequent samples from the same location and during the same time of the year. When planning to: establish a new pasture in a prepared seedbed, or interseed, or frost seed, sample at least six months before seeding.

Where to Have Samples Tested

Local University of Illinois Extension offices, Natural Resources Conservation Service offices, and fertilizer dealers can provide information on soil testing services available in your area. The Illinois Soil Testing Association, http://www.soiltesting.org/index.html is an organization that represents about 30 laboratories.

Submitting Sample

Most soil testing laboratories will provide bags for soil samples. Samples can be mailed to the laboratory. Be sure to label bags clearly (name, address, sample number, etc.) and indicate the sampling depth and that the sample represents pasture. Indicate if the pasture is grass, legume, or a grass-legume mixture.

Summary

Soil sampling, done correctly, is a best management practice and is the first step in developing strategies for a pasture fertilization program.

Where to Get Help

For more information contact the local office of the Natural Resources Conservation Service or University of Illinois Extension.

Acknowledgements

Information in this fact sheet was adapted from a number of sources, but primarily the Illinois Agronomy Handbook, 23rd edition. It is available at University of Illinois Extension offices and on the Internet at http://iah.aces.uiuc.edu/

Prepared by

Jim Morrison, University of Illinois Extension, Crop Systems Educator.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audio tape, etc.) should contact USDA’s TARGET Center at 202-720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, 1400 Independence Avenue, SW, Washington, DC 20250-9410 or call (202) 720-5964 (voice and TDD). USDA is an equal opportunity provider and employer.”

Fertility

Nutrient Cycling in Pastures

Illinois

Introduction

Many of the nutrients consumed by grazing animals are returned to the soil in the feces and urine. These animals also import nutrients to the pasture after consuming feeds purchased by the producer. This fact sheet addresses the importance of understanding and managing nutrient (mainly nitrogen, phosphorus, and potassium) cycling in pastures. It complements fact sheets titled “Soil Sampling and Testing” and “Pasture Fertilization”.

Essential Mineral Nutrients

Sixteen elements have been determined to be essential for growth and function of all plants. Carbon (C), hydrogen (H), and oxygen (O) are termed organic elements and are obtained from atmospheric carbon dioxide and water. Nitrogen (N), phosphorus (P), and potassium (K) are called primary nutrients. Calcium (Ca), magnesium (Mg), and sulfur (S) are referred to as secondary nutrients. Chlorine (Cl), boron (B), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), and molybdenum (Mo) are termed micronutrients-required but in very small quantities.

The goal of soil fertility management for pastures is to maintain the plant available pool of nutrients at a sufficient level to support quality forage production while protecting the environment.

Nutrient Cycling

TA nutrient cycle describes the flow of nutrients into, out of, and within a pasture.

Export (hay, meat, milk, soil erosion, nutrient leaching, and ammonia nitrogen volatilization) of nutrients from the pasture lowers the plant-available nutrient pool in the soil by moving nutrients out of the pasture instead of recycling them back into the soil pool.

Typically, hay and row crop fields have a high nutrient export while pastures are low-export systems for most nutrients. See Table 1.

Table 1. Estimated removal of nitrogen, phosphorus, and potassium from a field under two different management systems.

University of Missouri-Columbia, Dairy Grazing Manual, M168

Phosphorus and Potassium Cycling

Grazing animals will retain less than 15 percent of the phosphorus and potassium they ingest. The balance is excreted.

Since grazing animals are attracted to water, shade, and higher ground, these areas typically have higher concentrations of excretions, compared to where animals ingest the forage. Thus, a nutrient redistribution occurs in the pasture. For livestock manure to be effectively utilized, nutrient redistribution by grazing animals must be as uniform as possible.

In most cases, the distribution of feces and urine by grazing animals are independent of each other. This further reduces the evenness of redistribution since most phosphorus is contained in the feces and most potassium is contained in the urine.

If manure is well distributed in the pasture, there will be little loss or even an increase in soil test phosphorus and potassium values. Soil testing every three to four years will monitor the level of these two nutrients.

Nitrogen Cycling

Benefits of Management Grazing

A goal of a managed grazing system (grazer decides when, where, and for how long animals will graze a pasture/paddock) should be to enhance the uniformity of manure distribution. High stocking densities and short grazing periods are two ways to encourage uniform manure distribution. As grazing intensity increases, the time needed to have complete coverage of the pasture by manure decreases.

Summary

Grazing systems differ from hay systems and row crop systems in that a large portion of the nutrients consumed by animals during grazing is returned to the pasture in the form of manure. Managed grazing systems improve the recycling of nutrients in a pasture, minimizing but not eliminating the need for nutrient inputs.

Where to Get Help

For more information contact the local office of the Natural Resources Conservation Service or University of Illinois Extension.

Acknowledgements

Information in this fact sheet was adapted from the Missouri Grazing Manual, the University of Missouri Dairy Grazing Manual, and proceedings from the Nutrient Cycling in Forage Systems Conference, March 1996.

Prepared by

Jim Morrison, University of Illinois Extension, Crop Systems Educator.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audio tape, etc.) should contact USDA’s TARGET Center at 202-720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, 1400 Independence Avenue, SW, Washington, DC 20250-9410 or call (202) 720-5964 (voice and TDD). USDA is an equal opportunity provider and employer.”