Using Annual Forages To Beef Up Perennial Pastures

By Jim Gerrish

MAY, Idaho: There has been a tremendous surge in the use of annual forages over the last several years. Part of this has been driven by the increased use of annual cover crops in mixed farming-livestock production systems. There has been a spillover of interest in putting annual forages into existing perennial pastures. I am pretty sure I have received more questions on that topic in the last two to three years than I had in the previous 20-30 years combined.   

As all of you know, the USA is a huge country with a great diversity of environments and climatic conditions. This diversity of growing environments means the answer to the question of using annual forages to beef up perennial pastures has to be “It depends!”   

Part of the USA is dominated by warm-season grasses (The South) and part is dominated by cool-season grasses (The North).  Then we have everything in between where there is a mixture of both WSG & CSG. The most likely scenarios we would be looking at are putting cool-season annuals (CSA) into WSG or warm-season annuals (WSA) into CSG.   

A quick look at pasture use around the country shows us there is a long and successful history of overseeding perennial WSG pastures in the South with CSA.  Thousands of cattle producers across the South routinely interseed Bermudagrass and bahia grass pastures with annual ryegrass, cereal rye, oats, clovers, and vetch every year. This has been going on for at least 50 years.   

The reason this works so well is, throughout almost all the southern states, WSG experience true winter dormancy. That is, they completely shut off active growth in response to cooler nighttime temperatures.  Very few places in the continental USA sustain nighttime temperatures above 50 degrees F throughout the winter months. That means there are times of the year when the perennial sod is not competing for sunlight, water, and soil minerals.  This period of dormancy provides an opportunity for CSA to utilize these resources and dominate the landscape.   

A lot of these areas have a winter wet season meaning there is plenty of water available for the CSA to flourish. As often as not, the limitation for using CSA pasture effectively in the winter or early spring is the soil is too wet for cattle to graze.  Using no-till seeding helps keep the ground firmer and more usable compared to seeding the CSA on a tilled seedbed.   

Winter annuals seeded into perennial warm-season pastures is a proven double-cropping system that works well across the southern USA.  What about going the other way, putting warm-season annuals into cool-season perennial pastures?  

The broad experience is the WSA seeded into CSG is not nearly as successful a program. The answer for the difference is really pretty simple. In much of the USA where CSG dominate, the perennial grasses do not go fully dormant in the summer months. Even though growth may have slowed considerably, the cool-season perennial grasses and legumes are still actively growing. Thus, they are competing for sunlight, water, and soil minerals. WSA Seedlings are at much greater disadvantage in a cool-season sod compared to CSA seedlings in a dormant WSG sod.  Does this mean putting WSA into a CSG is a hopeless cause?No, it just requires a higher level of management and more attention to details compared to the generally successful reverse approach of CSA into a WSG.   

Hey, is everyone getting as tired of all these acronyms as I am?   

Let’s look at some of the keys to success for putting warm-season annuals into an existing cool-season pasture.  

In general it is easier to do an interseeding into a bunch grass stand like orchardgrass or timothy than it is to go into a sod like mooth bromegrass. While tall fescue is a bunch grass, historic severe grazing on tall fescue can make it perform more like a sod former. Even a semi-dormant sod former like smooth bromegrass can suck all of the moisture out of the soil for a depth of several inches making it very difficult for small seedlings to getting essential moisture during the early stablishment phase. When it does rain, the extensive root system of the existing sod is too competitive, especially if it is a light rain.  

If you have some pastures that are more bunch grass dominant, choose those for your interseeding efforts.  Severe grazing of the CSG through spring will lower the vigor of those grasses and reduce the competitive advantage of the existing sod. This is more effective on bunch grasses than sod-formers.   

What’s the downside of seeding annuals into perennial pastures? If you hope to maintain the perennial base that is out there, being really successful with your annual forage interseedings can lead to smothering the perennials. If the annual crops look like they are getting too much of an upper hand, you can use aggressive high stock density grazing to remove the annual crop as quickly as possible.   

Unfortunately, most graziers are a couple weeks too late before they realize the oncoming problem. Just another good reason to have an ongoing monitoring program where you are looking at every pasture on a regular basis. The bi-weekly pasture inventory would give you a better sense of where things were heading before you got to the cliff.  

The bottom line is that annuals seeded into perennials can extend the grazing season and give you more stock-days per acre, but using annuals on top of your perennial grasses successfully requires a higher level of management on an ongoing basis. Attention to the details is critical. It is way too easy to end up spending a lot more money on the annual component to get about the same outcome as the perennial pasture would have given you without the added expense. 

■  Jim Gerrish can be contacted at  www.americangrazinglands.com.<... order his books, click here.To get up close and personal attend theGrassroots of Grazing School in January 2018. Click here for more information. Only 26 attendees a school.