Tradeoffs in a forage system
Delayed Summer Grass Production in Louisiana
By: Dr. C. P. Bagley, Director
Beef Research Institute, Southern University, Baton Rouge, LA
Many Louisiana producers were concerned about our bermudagrass and bahiagrass delay in May, and lack of forage production this spring and summer 2024. The delayed summer forage production is widespread, but not at all farms. There are no scientific studies designed to demonstrate why this occurred, so we are left to explain this occurrence by observing many fields and pastures in the South.
It appears likely that two forces at work have caused the delayed forage production in bermudagrass and bahiagrass fields this spring and summer.
The historical drought in summer 2023 weakened grass stands across much of Louisiana, one of the hardest hit drought states that year.
The weakened grass stands in fall 2023 allowed ryegrass and clover stands to be significantly more productive over winter and spring than usual. Their prolific growth helped retard the emergence of summer grasses for three reasons: competition for soil nutrients/water, shading out, and an allelopathic effect.
According to the National Weather Service, south Louisiana was one of the hardest-hit drought areas in the US summer 2023, with many other areas of the South resulting in reduced forage growth and almost no hay production. Because of the unusual summer heat last year and record low rainfall, pastures were weakened and plants died, thinning the stands. Several producers knew their hay supplies would be limited, and planted ryegrass and clover to help boost production.
On the Ed O’Neal Farm in DeRidder, red clover was planted (pictured, photo taken 6/14/23) resulting in an outstanding stand of red clover along with ryegrass. One of Ed’s pastures was harvested as ryegrass baleage due to the outstanding forage yields in late spring.
However, this large growth of spring ryegrass and clover forage production can come with a price- -suppression of the emergence of bermudagrass and bahiagrass. All forages require water and sunlight for growth and production. But when you have 15 – 20 inch tall ryegrass standing, how is bermudagrass and bahiagrass supposed to emerge and compete? Nutrients were used up by the flourishing winter forages in March, April, and early May.
We held a Field Day at the O’Neal Farm May 30, and we observed pastures full of mature, brown ryegrass, plentiful green clover, and tiny sprigs of bermudagrass and bahiagrass that were just emerging in the pastures. We believe that the plentiful, thick ryegrass and clover essentially shaded out the later-emerging summer grasses.
There is also an issue with the “allelopathic” impacts of forages. shading out, Simply put, many forages and plants produce biochemicals/ toxins that inhibit the germination and growth of competing plants. For example, one of the worst forages showing this allopathic effect is alfalfa. Established stands of alfalfa produce chemicals that try and inhibit other seeds from germinating. In alfalfa-growing regions, it is common for alfalfa fields to lay fallow for one year and then replant alfalfa stands because of this chemical impact. Conversely, one of the forages least likely to produce these inhibiting chemicals is hairy vetch, which is why it is often thought of as being one of the best cover crops.
In the case of ryegrass, however, the allelopathic effect is also supported by it being an earlier-growing forage crop than bahiagrass in spring. Ryegrass flourishing in Louisiana’s March-April can shade out and “steal” more moisture, soil nutrients, and sunlight than the later-growing bermudagrass and bahiagrass that wants to begin growing in May. On top of that, generally, the larger the plant, the more natural toxins it can produce to suppress other forage crops.
So, the tradeoff was that the abundant production of ryegrass allowed an earlier end to hay feeding, but suppressed and delayed summer pasture growth.
On our three farms in the NRCS-supported rotational grazing study, we found that each of those three farms were able to graze longer during the 2023 drought than other farms in their areas that did not practice rotational grazing. Rotational grazing allows pastures to become taller during the rest periods, which resulted in larger plants and deeper roots. In a drought, those deeper roots allow the plants to reach down deeper in the soil profile and receive additional water and nutrients to continue to grow and be productive. In this circumstance, plant height came at an advantage, as the taller plants provided shade to help lower ground temperatures and keep the plant roots cooler. This double effect allowed these three farms to graze better through much of the drought than neighboring farms. However, in exceptional drought conditions, even rotational grazing cannot take the place of adequate rainfall. Toward the end of the drought, the conditions worsened for summer grazing, but improved for ryegrass and clover fall seeding by providing a naturally cleared off seed bed- a trade-off that resulted in the previously discussed bargain made between ryegrass and summer grasses in the following spring.
No natural event is without consequence, and our job as land managers is to facilitate, observe, and make decisions. Frequent observations and monitoring of pastures and cattle can help productivity. And even with close monitoring, sometimes Mother Nature still lets you know she is in charge! Decision-making from a forage manager often needs to pivot quickly, with close observation and changes as demanded by conditions. The pros and cons of forage grazing days/ longevity and nutrient content of the grasses should be considered. As we can see from the past year, longer ryegrass grazing days must be carefully weighed against the summer forage oppression that can happen, and sometimes there are tradeoffs. *
*Thank you to First South Farm Credit for sponsoring the waters for this pasture walk, and for the O'Neal family for providing lunch.*
-partial edits by Tara Morris, LGLCI-
Louisiana GLCI, Grazing, Grazing Lands, Deep South, Forages, Forage management, beef cattle, ryegrass, Deridder, Ragley,
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