Is it possible to increase the amount of grass produced in the same pasture? The answer is "maybe". Your semi-arid rangeland may have room to improve. But where do you start? A recent webinar by Pat Reece "Herbage Production Potential" outlines principles to understand.
Evaluate what the production potential of an ecological range site is. Soil characteristics, growing season, precipitation, evaporation rates and topography along with an inventory of existing grass species and current plant vigor can give a benchmark for what the production potential could be. The NRCS Web Soil Survey has resource tools that can be used to identify the ecological site and find what potential vegetation production could be. This, along with historical grazing records and on site evaluation, can give an indication of production potential.
Tall grass species are more productive than short grasses in terms of pounds of herbage produced. Sand bluestem and prairie sandreed will produce more pounds of forage than sedges and blue grama. Grass vigor and production will be reduced if pastures experience consecutive years of overgrazing, grazing repeatedly during the growing season at the same time every year, and drought conditions. These circumstances can result in tall grasses beginning to disappear, more "weedy" species being present, and more grazing tolerant short grasses becoming more abundant.
Healthy tall grasses have roots that can utilize water and nutrients deeper down in the soil profile. Stressed tall grasses and short grass species roots are not as deep. When the top soil starts to dry out, the deeper rooted plants have a better chance of surviving.
Herbage production potential is affected by many factors we cannot control. Precipitation, days in the growing season, soil characteristics, depth to water, and evaporation rates all impact how much grass can be grown.
However, we can improve rangeland condition with grazing management, such as how many animals we stock, when and for how long we graze, and providing adequate recovery time for grazed plants.
Indicators of resilient rangelands are the presence of preferred grasses that are diverse, vigorous, and relatively abundant. Residual standing plants include preferred species. There is also a diversity of native species, including grasses, forbs and shrubs.
Overgrazing affects semi-arid grasslands in two ways.
- Plant health. The preferred plant species cannot fully recover before livestock return to graze the pasture again.
- Microenvironment. There is not enough litter and residual herbage to capture rain and facilitate precipitation infiltration into the soil. Soil temperature extremes are greater when litter and residual herbage are deficient.
Deferred or rest rotations are grazing systems that can allow for plants to recover, especially if they have been overgrazed in the past. Grazing systems should change the pasture use sequence to provide opportunities for full growing season deferment from grazing in every pasture once every 3 or 4 years.
Plants also need favorable air temperature and abundant soil water, as well as "rest days" during the growing season, to fully recovery.
Historical data for most areas shows precipitation is below average (drought) for one-third of the years, above average one-third of the years, and average precipitation one-third of the years. Not every year is the same, and your stocking rate shouldn't be the same either. Plan to destock rangeland in the dry years and restock in the wet years.
Herbage production is impacted greatly by events we cannot control, but good grazing management is something we can adjust.