Proper Livestock Management and the Importance of Soil Health
Baton Rouge, La. - Grazing lands account for 55% of all privately owned lands in the U.S., yet the research focus on these lands related to soil health has been very limited. While crop lands and forested lands have been studied for their impacts on soil health, the Southern University Ag Center conducted one of the first studies in the U.S. focused on grazing lands. The study was conducted over a four-year period at three privately owned farms in the South Louisiana towns of DeRidder, Palmetto and Norwood. To evaluate the impacts of grazing management systems on forage productivity, pastures at each farm were sampled seven times per year for quality, yield, and botanical composition. Three fields at each farm were evaluated annually for "soil health" improvements twice per year (April and October) resulting from rotational grazing and increasing forage species diversity in the pastures. The grant for this project was funded by USDA Natural Resources Conservation Service (NRCS) with continuing involvement from that agency. Each year at all three farms “pasture walks” were held and open to the public and well attended by local famers and student groups. Over 300 people attended the pasture walks and demonstrations on soil health, forage measurements, and soil health.
A “rotational grazing management system” was employed at each farm and was based on a 30-day rest-rotation schedule. The number of paddocks at each farm were three, five, and 30 paddocks showing the different levels of management. The first farm with three paddocks used each pasture for grazing for about 10 days and then rested it for 20 days while other pastures were grazed. The final farm would graze a pasture for one day and rest the pasture for 29 days in the rotation. A 30-day grazing cycle allows a pasture to recover from grazing, and this schedule tends to maximize total forage yield in a pasture, with forage this age (30 days) still having very good forage quality attributes.
Forage quality is highest when grass is one-day old, but there are limited amounts. As the forage grows and ages, there is more yield, but quality is less. Good quality is maintained in forages until about day 30, so a 30-day rotational system tends to maximize high forage yield and good forage quality. Rotational grazing in this manner will usually allow an increased stocking rate of about 30% due to optimum forage productivity.
But maybe the most important thing to forages is what happens underground. The amount of root mass is related to the amount of top growth. If pastures are continuously grazed as one pasture, grasses stay relatively short as do roots. But in a graze-rotation system, the forages get taller, and the roots increase in mass and get deeper. More and deeper roots increase soil mass, soil organic matter, water holding capacity, and forage roots can reach farther down into the soil profile to capture necessary nutrients for improved forage growth rates. Those root channels also improve water infiltration rates and these pastures that are rotationally grazed usually have increased drought tolerance.
In this study we measured increasing soil organic matter caused by rotational grazing, which is critical to improved plant nutrition and water holding capacity. This study found large rises in soil organic matter which contributes to nitrogen (N) nutrition in plants. Plant growth rate is largely dependent on N as the enzyme system in plants that drive photosynthesis is driven by N levels in the plant. As N in the soil increases, plants take up more N, and more photosynthesis occurs to make plants grow faster. Each 1% of soil organic matter is about 1,000 pounds per acre of N, but much of that is in an organic form and not available to plants. Every 1% organic matter is equivalent to 20 – 30 lbs. per acre of N that acts like a plant fertilizer. With organic matter levels at 3% for many pastures, that is about 60 – 90 lbs. per acre of N, or about 130 -200 lbs. per acre of fertilizer. For plant growth, organic N must be converted into inorganic N, usually in the form of ammonia (NH3). The ammonia goes to the plant to make proteins for photosynthesis, which makes the plants capture more sunlight and grow faster.
As seen in this study, pastures can be easily and cheaply subdivided with inexpensive electric fences. One thing frequently noticed by farmers is that cattle become calmer with electric fences, mostly due to the closer and more frequent human contact they become used to.
Grazing lands are acritical component of the ecosystem in the U.S. Agriculture is the largest industry in the U.S., and beef cattle and calves are the largest agricultural commodity. In fact, of the four largest agronomic crops grown in the U.S., three are primarily grown as livestock feeds: corn, soybeans, and hay. Only wheat (# 2) is primarily grown for human consumption.
The two graduate students who worked on this study became well-versed in forage-livestock agriculture, graduating with M.S. degrees from Southern University. One is now a District Conservationist with the NRCS, the other is working on her Ph.D. at Auburn University in Agronomy.
For additional information on this study contact, Dr. Clyde Bagley, Vice Chancellor for Research at clyde_bagley@suagcenter.com.
