Stale Seedbeds: A Weed-Control Tool When Herbicide Choices are Limited

By W. Carroll Johnson, III, Ph.D., Agronomist and Weed Scientist
Herbicides that are typically used for
weed control in food plots cannot
be used in certified organic production

Interesting questions arise from telephone calls and e-mails. One series of weed-control questions came from a customer who had hunting rights on a certified organic dairy. Herbicides that are typically used for weed control in food plots cannot be used in certified organic production systems, and the customer needed guidance on how to manage weeds without compromising the dairy's organic certification. This is a unique and challenging question that closely parallels my area of research in my full-time job.
This question is equally relevant when multi-species forage blends are planted for food plots and the species have varying tolerance to herbicides. In both examples, the panic-fueled question is the same: “How are weeds managed without herbicides?” 

Forage crop production practices that suppress weeds and encourage crop growth are the foundation for any weed management system, in any crop. In situations where herbicides are not an option, cultural weed control transforms from a foundational practice to the primary means of weed control. A cultural weed control practice commonly recommended is the use of stale seedbeds, also called false seedbeds. A stale seedbed is a seedbed prepared several weeks or months prior to seeding the forage. Stale seedbed weed control works by stimulating the germination of non-dormant weed seed and simultaneously controlling newly emerged weed seedlings before planting food plots. 

There are a finite number of weed seeds in the soil and those that potentially infest crops are present in the upper two to three inches of the soil. Granted, the number of weed seeds may be in the millions per acre and there is no practical way to predict that number. Furthermore, weed seed germination varies according to weed species, soil type, geographical location, and current environmental conditions. As a general rule, repeated shallow tillage of stale seedbeds will stimulate germination of a large portion of the non-dormant weed seed in the upper two to three inches of the soil profile. Repeating shallow tillage at two-week intervals will simultaneously control the emerged weed seedlings and stimulate germination of a fresh batch of weed seed. Continuing this cycle of intermittent shallow tillage of stale seedbeds during fallow periods will reduce baseline weed densities before the forage blend is seeded. This does not deplete all viable weed seeds in the soil since some are dormant and located well below the depth of tillage. However, research has shown this system of cultural weed control is a proven means to substantially lower the baseline weed density. 

Compared to the U. S., Europe has traditionally relied more on cultural and mechanical weed control strategies than herbicides, and much of the useful supporting research is European. Studies conducted in Denmark showed that stale seedbed weed control reduced weed growth up to 84 percent compared to plantings that did not use stale seedbed weed control. It should be obvious that stale seedbed weed control is not a stand-alone weed control strategy. It is simply one tool in the weed control tool box that can be used in virtually every food plot system — a crescent wrench of sorts. 

There are three critical characteristics of a successful stale seedbed weed control program. First, start the process early, several weeks or months prior to seeding the forage blend if possible. Second, shallow-till the seedbeds at two-week intervals. Third, use an implement that thoroughly tills the top two to three inches of the soil. The best implement is a PTO-tiller since it is a shallow tillage implement that pulverizes the soil. However, two perpendicular passes with a disk harrow is an acceptable alternative. Regardless of the implement, repeat the process three or four times for maximum benefit. 

A variation on stale seedbed weed control is the use of a non-selective, broad-spectrum herbicide such as glyphosate (Roundup and generics) to control emerged weeds on the seedbed before planting forages. Glyphosate has basically no soil-residual properties and will not affect forages when applied before planting. The key to using glyphosate as a stale seedbed weed control tool is timing; weeds need to be emerged and actively growing for optimum performance. In addition, time is needed to allow glyphosate to translocate in the vascular system of weeds to the roots for optimum performance; meaning that treated weeds need to remain undisturbed for several days after treatment. 

Glyphosate for stale seedbed weed control is particularly useful where perennial weeds (briars, bramble, Johnson grass, common Bermuda grass, quack grass, etc.) infest the site. Seedbed tillage alone will not control perennial weeds outright, but glyphosate can provide valuable control of perennial weeds. In fact, the tandem system of stale seedbed tillage coupled with an application of glyphosate is probably the best stale seedbed weed control system, with the combination being synergistic to each component alone. 

For the tangible benefits of stale seedbed weed control, there are disadvantages that need to be considered. Frequent and intense stale seedbed tillage in not a good soil stewardship practice, particularly in areas where soil erosion is problematic. When done correctly, stale seedbed tillage eliminates all vegetation (i.e. weeds) short term and creates a condition for erosion. Secondly, stale seedbed tillage alters soil physical structure and can cause soil compaction. The degree to which this occurs varies according to tillage implement, frequency of tillage, and soil type. These are unfortunate outcomes that cannot be overlooked. 

In professional agricultural circles, there are many advocates of no-tillage crop production with a stated advantage of no-tillage being fewer weeds due to non-disturbed soil and weed suppression by cover or smother crops. While research data does not always support their position, they are repulsed by the idea of repeated stale seedbed tillage. I will not use this article as a means of refuting their contention. In fact, no-tillage advocates have legitimate points. 

So, we have a paradox; promote soil health and practice good soil stewardship by reducing or eliminating seedbed tillage; or intensively till seedbeds before planting forages to deplete weed seed. That is a tough choice. I have been beaten senseless by my organic crop production customers with the same argument. My response back to organic growers (and in our case customers who plant multispecies forage blends in food plots): How will weeds be controlled if tillage is removed? Pick your poison. When considered long-term, it makes sense to me as someone who studies weeds and personally struggles with weed control in food plots, that a system built around stale seedbed weed control does not have to be a permanent production practice. It can be gradually transformed into a minimum tillage system once baseline weed populations are reduced to a manageable level. 

This article began with a discussion about food plot management on a certified organic dairy and the need to manage food plots without compromising the owner’s organic certification. This real-world example parallels the constraints of weed control in food plots planted to a blend of several forage species. In both cases, the tools for successful weed control are limited and selective herbicides are not always an option. Study the entire system of forage crop production practices and focus on the weed control benefits that they provide. Stale seedbed weed control is a useful and versatile weed control strategy; a crescent wrench of sorts. While stale seedbed weed control is not stand-alone and certainly has a down-side, consider it to be the ‘go-to’ method to reduce weed populations and stay ahead of weeds in food plots.