It is not an unusual situation for people to suddenly find themselves the not-so-proud owner or long-term tenant of a previously abused or neglected pasture. In such situations, questions often arise as to what is the best plan of action to bring an abused pasture back to full productivity.
According to Chris Teutsch, a forage extension specialist at the University of Kentucky, there are a number of reasons why previously good pastures can turn bad. This includes too much or too little water; poor fertility or low soil pH; poor grazing or, in the case of a hayfield, cutting management; a poor choice of forage species; and an influx of weeds probably caused by one of the previously mentioned factors. Often a poor pasture is the result of a combination of several negative stresses.
“Pasture renovation doesn’t always mean reseeding,” Teutsch told last fall’s Kentucky Grazing School. “In truth, spraying an old pasture and then reseeding should be considered a last resort option. We can often renovate a pasture without reseeding it.”
Prepare the soil
The first step to improved pasture productivity is to look below ground level. Teutsch defined soil as a dynamic natural body consisting of mineral and organic solids, gases, liquids and living organisms, which can serve as a medium for plant growth.
“Underground, in a healthy pasture, scientists have determined that we should have about a ton of bacteria, a ton of actinomycetes, 3 tons of fungi and over 600 pounds of earthworms per acre,” Teutsch said. “When we manage the aboveground with good grazing techniques, we also improve the underground ecosystem, and this is very important to keep in mind.”
From a soil fertility point of view, Teutsch reminded the participants of Liebig’s Law of the Minimum, which states: “The level of plant production cannot be higher than that allowed by the most limiting of essential plant growth factors.”
“It’s going to take a holistic approach to rejuvenate pastures,” Teutsch said. “Often it will not be enough to identify just one limiting factor.”
A major advantage of well-managed grazing systems is that 80% to 90% of the nutrients applied through fertiliser, manure, legumes and forage are returned to the pasture in manure and urine. “This is a huge advantage compared to hay and other cropping systems,” noted Teutsch.
The feed specialist warned that it is up to the pasture manager to ensure that nutrients are distributed evenly across the pasture to prevent fertility levels from rising excessively in some areas while decreasing in others. This is where rotational grazing systems with multiple sites for water and shade are important to prevent animals from congregating in the same area.
Where hay is removed from fields or pastures, Teutsch noted that potassium levels can be drawn down quickly unless fertilizer is applied or the hay is returned to the same field. Many common hay species remove nearly 60 pounds per ton of potassium as K2O. “It can be a positive situation in the case where hay is purchased and brought to the farm,” he said. “Each ton of hay is going to have about $78 worth of nutrients at today’s fertilizer prices, but it’s important to feed the hay where the nutrients are most needed.”
Soil testing is going to be critical to confirm which nutrients are needed or not needed. This is especially true when fertilizer prices are high, Teutsch claimed.
Apart from documenting fertility status, soil testing is important to determine soil pH. “Improper pH is a major limiting factor in forage production because it reduces nutrient availability and nitrogen fixation by legumes,” Teutsch said. “Calcing of pastures will both neutralize soil acidity and provide calcium and magnesium.”
The extension specialist recommends a minimum soil pH level of 5.8 to 6 for pure grass stands, 6 to 6.4 for grass-clover stands and 6.5 to 6.8 for grass-alfalfa stands. “Right now, if you need lime, it may be your best buy because it will make existing soil nutrients more available to the plant without buying fertilizer,” Teutsch said.
The power of legumes
“Nitrogen fixation is the second most important biological process on earth; it’s just behind photosynthesis,” noted Teutsch. “For this reason, legumes provide significant benefits in grazing systems by providing nitrogen, which improves grass yield, forage quality, summer growth and animal performance. Legumes also help mitigate the effects of toxic fescue,” he added.
Most of the transfer of nitrogen between legume and grass takes place by the animal through the deposition of dung and urine. It can also occur when the legume plant tissues and roots die and decompose. A strong nitrogen cycle in a pasture takes several years to develop and maintain.
Teutsch suggested that legumes should make up 20% to 30% of the pasture. He said to add lime and fertilize according to the needs of the legumes, which can be transplanted in late winter. Frost sowing red clover and white clover generally results in the greatest success. For pastures that are not fertile, Teutsch suggested using annual lespedeza, which is more forgiving of low soil nutrient status.
“How a pasture is grazed can affect the botanical composition,” noted the forage specialist. “If you leave too much residue, it will tend to favor the grass. It is also important to use rotational stock, which makes it much easier to manage through a drought and maintain desirable forage species.”
Pasture renovation does not have to involve a complete kill and reseed. With corrections in soil fertility, the development of perpetual nutrient cycles, the establishment of legumes, and flexible, rotational grazing, poor pastures can be transformed into highly productive pastures.
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