Most cattle producers view their primary function as that of producing animals – more specifically, beef. However, in most cases the actual role the cattle producer plays is not just that of producing beef. More accurately is a role of turning grass into beef. Thus, the average cattleman is also required to be an accomplished grass farmer. And while a given producer may not provide grass per se to his cattle (perhaps he produces alfalfa, clover, vetch, possibly soybeans for hay) he is still providing a high fiber nutrient source that is the natural feedstuff for ruminant animals and which he can produce on his own land.
Cost effective forage production as it applies to beef cattle nutrition is a factor of two steps. 1) providing the appropriate nutrients to feed the plant to optimize it's growth and 2) feeding that plant to the animal to optimize the animal's growth. So it is necessary to evaluate two phases of the study of nutrition – plant nutrition and animal nutrition.
Of the more powerful tools available to provide information for this process is the analysis of soils and forages. This is especially true as we consider the rapidly increasing cost of fertilization. To best assess which analysis to use, the soil must be tested in order to get the most bang for your fertilizer dollar. So let's start with soils. Soil testing and analysis provides us with a picture of the nutrients available in the soil. More accurately, it is a process by which elements such as nitrogen, phosphorus, potassium, calcium, magnesium, sodium, sulfur, manganese, copper and zinc are chemically removed from the soil and measured for their "plant available" content within the sample. The quantity of available nutrients in the sample determines the amount of fertilizer or nutritional supplement that is recommended to meet the plant's growth needs. A soil test also measures soil pH, humic or organic matter and exchangeable acidity. These analyses indicate whether lime (limestone, calcium) is needed and, if so, how much to apply.
Forage testing allows us to balance rations, reducing costs and improving overall nutritional plane the herd is on, thereby improving performance and profits. It gives us a picture of what the current status of forage nutrient density is and can help the producer improve future crop management if present forage is of unsatisfactory quality. Finally, it can help us evaluate the value of the plant material as a nutrient source and help us determine equitable prices for feedstuffs based on nutritive value.
Why Should a Producer Soil Test?
There are numerous reasons to test and include:
• to optimize crop production.
• to improve the soil's nutritional balance.
• to save money and conserve energy by applying only the amount of fertilizer needed.
• to aid in the diagnosis of plant culture problems.
• to protect the environment from contamination by runoff and leaching of excess fertilizers.
• to identify soils contaminated with lead or other heavy metals.
A soil test can be a valuable tool in assessing and preventing horticultural, agronomic, and some environmental problems. The tests listed above do
not identify plant growth problems associated with soil drainage, insects, plant diseases (whether soil-borne or not), weeds, winter injury and the misuse of pesticides. These issues have to be addressed separately and provide additional management data.
How to Take a Soil Sample
In many states, soil tests such as those conducted in the soil testing laboratories in many land grant universities will help you to develop and maintain a more productive soil and to increase net returns per acre by providing information on the available nutrient content and fertility status of the soil. There are also numerous private and corporate laboratories which will provide an assay on soil samples for a small fee. Irregardless of the testing facility, this can help the producer select the correct kind and amount of fertilizer and liming material.
Taking the sample itself is a critical task and must be done carefully. Remember, a soil sample weighing approximately 1/2 pound is used to represent from 2 to 40 million pounds of soil in the field. Be sure to consider the following:
soil sample should represent only one soil type or soil condition.
Sample different soil types separately. Thus hill slopes, well-drained valley floors, and poorly drained areas should all be sampled separately. Areas producing differenent forages or areas with different management histories, should be sampled separately. For example, a separate sample should be taken from each of the four following sampling areas: forage on poorly drained soil, forage on well-drained soil, wheat on well-drained valley floor soil, and wheat on hill slope soil.
2) A good soil sample should represent the area.
Each sample should consist of sub-samples taken from 10 to 15 locations within the sampling area. If an area has previously had unusual fertilization techniques applied, such as an area where vegetable crops were grown and fertilizer was banded by crop, more sub-samples should be taken, possibly 20 to 30.
3) Avoid small unusual areas.
Take separate soil samples from unusual areas (old cattle traps or other high concentration areas such as where hay was fed and accumulated) that are large enough to fertilize separately.
4) Take soil sample to the correct depth.
Unless otherwise specified, soil samples are taken to plow depth -- usually, from the surface down to about six to nine inches. When deeper soil samples are required, remove then from the bottom of the holes from which you took the surface sample.
5) Avoid contaminating the sample.
•Use clean sampling tools.
•Avoid contaminating the sample during mixing or packaging.
•A small amount of fertilizer residue on tools or hands, for instance, can cause serious contamination of the soil sample.
•Galvanized brass, or bronze sampling tools should not be used for soil samples where a soil test for micronutrients such as zinc is to be run.
6) The soil sample should be carefully mixed and packaged.
Place soil sub-samples in a clean container and mix thoroughly. Fill the soil sample bag with the soil mixture and identify clearly on the bag as well as on a log sheet or map.
7) Mailing the soil sample.
Print the necessary information on the sample bag. Be sure to number each sample and keep a record on the fields sampled. Don't use a paper bag for soil sample. Most labs will provide you with a sample information sheet. Fill out information sheet and mail it at the same time the sample is mailed. In many cases you will need to include payment to cover the cost of the soil test. Recommendations are based on the results of fertilizer experiments, soil surveys, and results obtained by farmers in the state or area in which you reside or where the field or pasture is located.
Once you have received the results, read the assay sheets carefully. Normally these printouts will give you a report on the current status of the soil and the levels of the various nutrients found. Subsequently it will give you guidelines as to the level of the various nutrients needed to promote desired plant production. One thing that we have to remember is that soil testing and subsequent fertilization, while a valuable tool will be of limited effectiveness in the event of very dry weather conditions and low soil moisture.
How Often Should Soils be Tested?
Perennial crops such as alfalfa, grass seed, and permanent pasture, should be tested prior to seeding and subsequently at least every three years. The initial soil test prior to seeding, is particularly important.
For annual crops, the soil should be tested annually before planting.
Soil testing well in advance of planting is important, particularly in the case of acid soils where liming is likely to be needed. Lime should be applied and mixed with the soil several months prior to seeding, since lime reacts slowly with the soil.
We've spent a fair bit of time on forage testing in the past but this is a good opportunity to reinforce what has been discussed.
Production of quality forages is not something that occurs overnight. It takes time and investments in soil sampling as discussed, fertilization and subsequent forage sampling. It also requires timely harvesting and appropriate storage methods. All this said, the emphasis here is knowing what you are starting with and where you are as you go through this process. One of the best investments you can make in a given year is to forage test and use a forage testing procedure which includes analyses for the fiber components discussed above. Many times a producer tests only for dry matter, protein, TDN and maybe a few minerals. This information is helpful but does not provide an indicator of maturity and digestibility of the plant material. One thing to understand is that the values shown in a forage test are not totally available to the cow. As you see the fiber numbers discussed increasing, we can assume that the digestibility and subsequently the availability of the other nutrients such as protein is decreasing.
It is helpful to test growing forages periodically to determine where they stand on nutrient content and digestibility indicators. It can also give us an indicator of how good of a job we are doing in the soil and plant fertility department. Normally, what we see as the spring and summer months progress is an increase in the overall fiber components of growing forages which is less closely related to actual plant maturity as it is to climatic and seasonal conditions. For this reason it is advisable to keep growing forages somewhat shorter and in the growing stage and out of the adult/seed head production stage. Also, as stores of forage are harvested for late fall and winter months, it is good to know how each cutting tests. In this manner, you can determine which stored forage lot is to be fed to which group of cattle and how supplementation levels need to be altered to best match this deficiency. A quick sampling procedure would include the following:
1) Group hay cuttings together so they can be easily distinguished. In other words, if stacking outside or in a barn, keep all the hay from a given cutting in one place. If necessary, identify where the group stops and starts. A given cutting from a given field needs to be grouped in a specific area so you can modify your supplementation program as you change feeding from one grouping or lot to another. Also, if possible, group bales from specific parts of a given field that may have distinctive or different soil characteristics. In other words, if a given field has a section that is very sandy and another that is more clay-based, try to separate these groups of hay. Also, document or map where your groups are positioned to help you remember what is where.
2) Prepare in advance by having the correct tools. You will need a forage probe, pen and paper, clean cardboard box, zip-lock bags and a permanent marker. Several different forage probes exist on the market, each designed to take a 3/4 to 1 inch core, approximately 12 to 18” into a bale. Probe types include those which can be “drilled” in using a brace or a cordless drill, those which are driven in using a mallet or hammer, etc.
3) Sample each cutting of hay shortly after it is baled. Sample at least 10 percent of the bales in a given cutting or group of no more than 80 to 100 bales. Normally it works best when the hay has been moved in to place in your hay trap or in the barn. At this point go through and randomly sample 10 percent of the bales. After each bale is probed, empty the sample into the cardboard box. Once all the samples have been obtained, thoroughly mix the samples and remove enough to fill a quart-sized zip-lock bag 1/2 to 3/4 of the way full. Force as much air out of the bag as possible and seal. Label the sample with the permanent marker listing your name, the date, location and cutting. Once all your samples have been collected in this manner they can be placed in a large envelope or small box for shipment to the lab.
4) With your samples, send along a cover letter listing your name and address along with a list of the samples you are including and include for each sample the same data as written on the sample bag. This simply helps the lab keep track of your samples.
5) Depending on the lab you use, your test results may take ten days to two weeks to get to you from the day you mail them. Once you receive these results, closely evaluate the data. From this information you can determine which forage is of better quality and which hay needs to be fed to given groups of cows at any given point in time. This also tells you that when you start feeding a different grouping or cutting of hay you may have to increase or decrease supplementation.
Soil and forage tests can provide you with a huge amount of valuable data to help in your decision making process and are always a good investment if performed carefully and judiciously. The time and dollars you spend on obtaining this information can save you countless dollars down the road.
Dr. Steve Blezinger is and nutritional and management consultant with an office in Sulphur Springs Texas. He can be reached at CR 4711 Sulphur Springs, TX 75482, by phone at (903) 885-7992 or by e-mail at firstname.lastname@example.org.