Research adds proof: High stock density builds forage
New data from West Texas adds to the proof higher stock densities can improve soil and forage health.
A seven-year study measuring forage density, bare ground and algal capping, and also declining vs. thriving plant life, has shown higher-stock-density grazing decreases bare ground and improves plant health. The measurements were taken along transect lines in the David West Ranch near Ozona, Texas, which is run by Holistic Management International.
This might not be news to some high-end graziers, who typically keep their own grazing records and may do a good job measuring changes in forage health and plant species shifts. However, not much data of this type is in the public realm.
Specifically, this study measured forage progression along 13 transect lines spread through various paddocks on the ranch. A transect line is typically a permanent straight line from which land managers sample biological measurements and analyze data to determine whether plant species health is improving or declining.
The managers and researchers found that overall, from 2002 to 2008, bare ground on the ranch decreased from 70% of the surface area to 40%. Said another way, grass and plant cover increased from about one-third of the soil surface to nearly two-thirds of the soil surface during the seven years.
The 11,000-acre West Ranch is in a dry, rough and brushy part of West Texas and had been completely destocked for 15 years prior to Holistic Management International taking over.
As the managers increased the number of paddocks and the number of animals through the years of the study, they were able to increase the stock density, or the number of animals or pounds of animals per acre at any given time.
Throughout the seven years the managers varied stocking rate, grazing days and herd size somewhat to match highly varied rainfall. Some years the more typical 8 to 17 inches of rain fell. But two years rainfall hit 41 inches.
Soil capping with algal/lichen growth has declined. Capping makes it nearly impossible for new forage seedlings to establish on bare ground. The hoof action of livestock can break up capping and allow new plants to grow.
In the early years of the study, old capping held on stubbornly with the application of lighter stocking densities, which likely didn’t bunch the animals enough to affect it much. Broken capping seemed to climb a little and then fall back. New, immature capping rose dramatically.
By the last two years of the study — coincidentally with stock densities on the rise — new and old capping dropped toward zero percent and the measurement on broken capping shot up dramatically.
The density of normal, healthy grasses rose from just above 10% to nearly 90%. By 2007, the amount of dying grasses counted in the transects fell to nothing, and the amount of over-rested grasses fell to about 10%.
A graph of the percentage of forage-covered soil vs. algae-capped soil shows a direct inverse relationship. As the capping decreased, the forage increased.
It’s also worth noting this study shows a financial payoff for healthier soil and forage. As the forage got better, the ranch was able to stock more animals. Naturally, the stocking rate was varied to match rainfall, but it began with 270 animals in a 14-inch rainfall year and finished with 328 animals in a 10-inch rainfall year.
This article published in the May, 2010 edition of BEEF PRODUCER.