It takes grass to grow grass
I’ve been working on this grazing stuff for many years. One of the expressions often stated was – “it takes grass to grow grass,” we’d all nod our heads in agreement. In hindsight, perhaps I was too embarrassed to admit I did not understand what that truly meant. It was years of learning and gaining experience and understanding about how grazing research supports that exact notion.
The researcher, F.J. Crider, worked for the Soil Conservation Service and conducted a series of experiments on plant defoliation on both cool and warm season grasses.
In one experiment, with a single harvest, he clipped plants at 10% increments, so clipped 10% and left 90%, clipped 20% left 80% and so on. The results were stunning. At up to 40% defoliation (leaving 60% behind) resulted in 0% of the roots stopping growth.
As soon as more than 50% of the plant material was removed, this level and higher dramatically increased the percentage of roots which stopped growing. When 80% of the forage was removed, 100% of the roots stopped growing. Note: This is also the source of the notion “graze half, leave half”.
It took anywhere from 6-18 days with an average of 11 days, for the roots to begin re-growing and new top growth (leaves) to appear. If we return to a paddock before the plant begins to re-grow (or maybe we have never left the paddock), this implies that the plant never has that opportunity to regrow, nor recharged its’ stored carbohydrates (energy) in the crown. It will become weaker, diminished and less productive. Note that it is 11 days BEFORE the roots START to recover, the plant still has not recovered yet.
In a second similar experiment, he repeatedly defoliated the plants at the same levels to simulate the effect of rotational grazing throughout the season. In this trial, repeated 70% or more defoliation, caused roots to stop growing for an average of 33 days.
We need roots to supply the leaves with the building materials for growth and to support the plant and leaves to capture energy from sunlight and produce the energy in sugars and starches to feed the roots and soil. One is in balance with another.
When we have bare ground, it represents a missed opportunity to capture free sunlight and convert it into something ruminant livestock can utilize – forage.
The leaf is the factory for the plant, a solar panel. If too much of the leaf is harvested, the water and nutrients back up, there’s no place to process them. The plant needs to build a new factory (leaves) before it can process what the roots supply, and the roots are not being supplied with sugar (energy) to work.
When our pasture plants continue to grow vigorously, recovery time is quicker, more forage is grown throughout the season, supporting our livestock and our livelihoods.
Additionally, as plants are actively growing they are also feeding a portion of the sugars they produce to support soil life. How well would we all work, if we didn’t have a good meal for 33 days? When we manage pasture well over time, soil health improves, soil organic matter increases, water infiltration and storage also increase enabling the soil to grow even more forage supporting more grazing, improving profits.
If you would not cut your alfalfa before it has recovered, why would you graze your pasture before it too was recovered?
Always remember – It Takes Grass to Grow Grass.
Gene Schriefer is an Outreach Specialist with Extension, UW-Madison