Use plant vigor as an indicator of pasture performance
Posted on: Sep 26, 2012
Plant vigor provides a quick and easy indicator to evaluate past grazing management. When evaluating plant vigor, an observer asks these questions: Are the pasture plants green and growing relative to recent climatic events? Are plants producing seed? Are plants achieving expected stature? Are plants firmly rooted to the soil surface? If the answer to any of these questions is "no," then resoruce managers must examine their grazing management practices.
Consider the following photo, taken on a Montana ranch in early June 2012. This photo shows a pasture plants whose stature, color, and growth rate are well below historical observations. Further, plant productivity and anticipated stocking rate in animal days per acre is roughly half of long-term expectations.
A review of this ranch's grazing records shows that this pasture experienced long grazing durations and excessive utilization rates in 2011. As a result, this pasture requires much recovery time in the current growing season to allow plants a chance to regrow. Financially, the gains that were realized last year by poor management produced a net loss in income for this year's grazing operation. This example illustrates the importance of good grazing management through time, and plant vigor is a terrific indicator providing insight into corrective management actions.
Likewise, the following photo shows a Wyoming ranch that received nearly an inch of rain in the past two weeks, yet the pasture appears brown. The plants appear as if they are going dormant in the early growing season: they appear to possess low plant vigor. Improving plant vigor and overall plant productivity will require recovery time to be built into the grazing plan. In time, these plants should regain their vigor, and the pasture's performance will improve, but this ranch risks negatively impacting the revenue that may be generated from this pasture by leaving cattle for such long durations.