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Challenges to using native grasses for forage production

Patrick Keyser for Progressive Forage Published on 13 July 2022

Despite the many positive attributes of native grasses, these grasses, like all forages, have their drawbacks.

There are four such issues that present challenges to their use for forage production: difficulty in establishment, lost forage production during the establishment year, more attention required for proper management and a shorter production season than some of the dominant cool-season perennials. Each of these challenges is addressed below.

Challenging establishment

Native grasses most commonly used for forage production in the eastern U.S. (big bluestem, eastern gamagrass, indiangrass, little bluestem and switchgrass) are all considered late-successional species within grassland ecosystems. Thus, they are not adapted to rapid exploitation of disturbed sites. Put another way, they are all slow to establish; they are “distance runners” not “sprinters.” Keep in mind though, this is generally true of all of our perennial forage grasses. None of these species are as easy to establish as the annuals commonly used in forage production, such as sorghum-sudangrass hybrids, millets, rye or wheat. And with any perennial, there are some basic challenges to establishment – all require high-quality seedbeds with excellent competition control and shallow seeding depths. All of these are things that farmers can, more or less, control. And, of course, establishment success for all of these species, including the annuals, requires adequate and timely rain, something none of us can control.

Native grasses present an additional challenge though, at least compared to cool-season perennials, because they germinate slowly. Much like seeded bermudagrass, native grasses require 20-24 days to begin to germinate in appreciable numbers. Thus, even where competition control has been excellent, the long interval until seedlings emerge can allow weeds to germinate and once again become competitive. Furthermore, native grass seedlings prioritize root growth over top growth, leaving them vulnerable to developing canopies of rapidly growing annual weeds. Where good agronomic practices are not implemented, these factors can contribute to high stand failure rates. On the other hand, with good, pre-planting competition control, high-quality seedbeds and diligent post-planting weed control, establishment success rates are high – 85%-95% on the initial attempt. Where failures do occur despite good practices, it is usually a result of drought or excessive rain, which fosters rapid development of weeds. Nevertheless, the limited margin of error when establishing these small-seeded species (eastern gamagrass is an exception, having large seeds) makes native grass establishment challenging. One promising development is recent advances in plant breeding that have led to cultivars with substantially improved seedling vigor. These cultivars are expected to be commercially available by 2022.

Planting native grasses also requires an outlay of the producer’s time and labor for implementing the good agronomic practices mentioned earlier. And that clock starts running well before planting season when pre-planting weed control is initiated. There are also inescapable costs associated with a new planting. These may include herbicides, application of those herbicides, seed, drill rental and follow-up spraying/herbicides. A reasonable estimate of typical out-of-pocket costs would be $225-$315 per acre. Of course, actual costs for any particular planting project will vary based on specific circumstances. For instance, the $315 figure just mentioned was based on seed costs of $150 per acre, whereas the $225 figure was based on seed costs of $57 per acre. Both figures include custom application and/or equipment rental as well. Regardless of the actual cost, this investment presents a risk – as do all planting exercises regardless of the species in question. Furthermore, costs and risks associated with establishing native grasses should not be compared to doing nothing, assuming the site needed to be planted or renovated regardless of the species to be planted.

Lost forage production during establishment

Because of the need for newly emerged seedlings to develop their deep root systems and produce enough above-ground growth to be competitive, use of seedling stands for grazing or hay production is not recommended. Even in a best-case scenario, with initial competition control not being implemented until late March and, therefore, forage still available up until that point, there would not be any forage produced until early May of the second year, about 13 months later. For many producers, this is a serious challenge, especially where existing herd size and grass availability leave little management flexibility.

Challenging management

Compared to other commonly used forages such as tall fescue, bermudagrass and bahiagrass (Paspalum notatum), native grasses require more management to maintain vigorous, productive stands. This is largely because of their tall growth habit and how they store energy. Their rapid early-summer growth also contributes to the challenge. Because of their height, the optimum range in which to maintain canopies is considerably taller than what we are accustomed to with other forages that have shorter growth habits. It is important for managers to recognize and become accustomed to these taller canopy height targets. Attempting to graze native grasses as closely as more conventional forages will, over time, result in weakened, less-productive stands and greater weed pressure. Collectively, these factors mean that more timely adjustments to stocking are required for native grasses to ensure appropriate canopy targets are maintained.

However, if some care is taken in monitoring canopies and making appropriate adjustments in stocking, native grasses are not difficult to manage. It is also important to recognize that native grasses are much more resilient to mismanagement than is commonly recognized. Severe overgrazing can be accommodated by simply providing longer rest periods. What is critical, though, is to avoid repeated and/or prolonged overgrazing. Maintaining short canopies for a full season or repeated bouts of excessive canopy reduction over a period of a few years is what leads to more serious problems. Even then, extended rest periods (up to a season long) and perhaps some weed control can be effective in restoring the stand. In situations where the stand has become too tall, either mob grazing (high stock densities for short intervals) or a hay harvest can easily correct this problem. Although rotational grazing has been commonly recommended for natives, they can be readily managed under other approaches including various continuous grazing strategies, management intensive grazing, patch-burn grazing or some combination of hay harvest and aftermath grazing. The point is that as long as appropriate canopy heights are maintained, grazing management can be quite flexible and stands can remain productive for decades.

Short season length

Native grasses, depending on the species in question, can be grazed from as early as late April (eastern gamagrass) through mid-September (indiangrass) in the mid-South, a period of approximately 130 days. That period will be somewhat longer at lower latitudes and several weeks shorter further north. However, toward the end of this period (after mid- to late August), the quantity and quality of forage will diminish. But even with the assumption of a 130-day grazing season, that still leaves 235 days during which no forage is produced. In comparison with tall fescue, this is a considerably shorter grazing season. For some producers, this can be a concern. However, for others the benefit of having a productive warm-season forage within the operation outweighs the shorter grazing season. It is worth noting that the grazing season for bermudagrass in the mid-South is generally similar to that for natives, about 130 days but with the window shifted a week or two later in the spring. Thus, the same question has to be answered regarding use of any warm-season perennial within a forage program, not just native grasses.

Summary

Producers should evaluate each of the issues addressed above as they consider adopting warm-season native grasses into their program. However, each should be weighed in context. There is no doubt that these species present challenges in establishment. It is also true that success rates with good agronomic practices are above 85% and that any perennial grass has many of the same issues. Lost forage production during the seedling year is a serious concern for many producers, but, again, there is such a period for any perennial, albeit a notably shorter one for cool-season species.

Much has been said about the difficulty in managing native grasses once established. However, with some attention to canopies (something we should be doing with any forage) and an appreciation for their taller growth habit, good management can be readily achieved. The trade-off between a productive summer forage and several months where these same stands are dormant must also be weighed. Together, all of these challenges must be considered in making the decision to adopt these grasses.  end mark

This article was derived from Patrick Keyser’s new book Native Grass Forages for the Eastern U.S.

Patrick Keyser
  • Patrick Keyser

  • University of Tennessee
  • Institute of Agriculture
  • Center for Native Grasslands
  • Email Patrick Keyser

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