How does Integrated Weed Management get less expensive over time?

Reducing Glyphosate Usage: A Cost-Effective Approach Through Integrated Weed Management

The council is looking to reduce glyphosate usage, but previous attempts to simply reduce spraying frequency have resulted in increased weed growth. The assumption is that eliminating spraying entirely would necessitate even more frequent, expensive, and potentially less effective interventions. However, this perspective overlooks the significant benefits of weed prevention through Integrated Weed Management (IWM).

Although this is a common framing of the question, it only accepts reactive weedkilling methods as possible solutions and fails to appreciate the massive benefits of weed prevention in its various forms.

The majority of the weeds we are talking about are occuring on hard surfaces, such as pavements, footpaths and roads.

They grow in the soil which has accumulated, usually at the edges of the surface, as a result of detritus build up. 

Quantifying the effect of soil buildup on the weed burden -

To quantify the effects of this soil build up, lets look at an example;

I just read a post on Linkedin by one of our customers - North Lincolnshire Council. They have been using our weedbrushes to reclaim footpaths that have been neglected for quite a number of years. My most generous guess would be that the footpath in question has not seen it's original edge since 2010 when budgets were cut after the financial crisis in 2008 and the following change in government. Which gives us a timescale of 15 years... in reality, it maybe a quite a bit longer than this, perhaps even as far back as the introduction of compulsory competitive tendering with The Local Government Act in 1988, which extended CCT to services like refuse collection and ground maintenance. Extending the timeframe for this would improve the maths we are about to do in my favour.

The Council just completed reclaiming a 1.11 mile stretch of path, which resulted in the removal of just over 100 Tonnes of soil and detritus. 

This would be equal to about 76 cubic meters of soil in approximate terms. 

If we think about the annual biomass of the weeds generated in that soil -

Gemini estimates a range of between 50 - 200kg dry weight (once the plant matter has dried out) of a typical verge plant such as ryegrass (per cubic meter of soil). So let's assume an average figure in the middle of that range as 125kg of weeds per year for each cubic meter.

Putting these figures together shows us that the council have just removed the potential to grow 125kg of dry plant weight across each of the 76 cubic meters, which is a total potential of 9.5 tonnes dry weight of weeds that would have been treated by weedkiller.

This was a big operation - but here's where some of our savings start to come in...

If we assume an evenly distributed re-establishment of the accumulated soil every year - (which is not the case, it actually snowballs over time, but let's be generous and assume it anyway), then the following year they would only have accumulated about 5 cubic meters of soil along this same mile of road. 

The growing potential of this 5 cubic meters is just 625kg dry weight of plant biomass - compared to the 9.5 tonnes the previous year. 

So, by simply removing detritus and soil from hard surfaces we have reduced the overall biomass of weeds we need to treat in that area by over 90% every year. This alone results in a massive reduction in the amount of weed control that needs to be administered. If we can reduce or minimise the weed burden, then weed control becomes cheaper, because we can treat it with far less weight of chemical if that's how you want to proceed. 

Now going to year 2 - We only have 5 cubic meters of soil to remove from the footpath, which takes a fraction of the time it took to remove 76 cubic meters of soil, there's only 5 cubic meters of soil to dispose of, and far less lorries needed to transport it, far less labour needed to remove and handle it, far less fuel... you get the idea. 

The gains don't stop there...

How soil depth affects the weed burden -

Having removed this much soil from the surface, the soil that returns will generally be much shallower on average than it was after the extended period of buildup, so the types of weeds that are able to grow in the soil will be different. The soil will go from being a great home for fast growing perennials with deep root systems and large foliage to only being suitable for small annuals with shallow root structures. This alters not only the biomass of the weed burden, but its resistance to other methods of weed control too. You can read research on this here if you need to.

This change in the type of weeds that grow will have a couple of benefits which we should consider in our weed management strategy. 

1. Firstly, the weeds in this shallower soil have less biomass than larger plants that grow from deeper soil, so the weed burden will be reduced.

1. Secondly and more profoundly, these smaller, shallower rooted annuals are much easier to treat with alternaitve methods of weed control to chemical, such as hot air or hot water. This means that treating the plants in the shallower soil will require far fewer treatments with heat than killing the weeds in the deeper soil. 

Maximising the benefits of heat to further reduce the weed burden.

Having read our guide on weed prevention, the council in question might now decide to treat the new weed growth early in its lifecycle with a couple of applications of heat. Heat can reliably be used early in the season because it is more impervious to bad weather than its chemical counterparts, enabling you to plan treatments much more predictably.

Heat will not only kill these small young plants quite easily, it can also have the effect of sterylising seeds, killing germinated seeds and preventing the plants from reaching an age where they will go to seed. In fact when weeds are young, they are primarily focused on growth and haven't yet put much energy into reproduction. This means they haven't produced many seeds, or in some cases, any seeds at all. So killing them at an early stage can massively reduce the weed burden going forwards by reducing the seedbank. 

Let's imagine a common weed, like chickweed (Stellaria media).

1. Early Treatment (March): If you treat chickweed in March when it's small, it might only have a few leaves and no flowers yet. You'd prevent it from producing any seeds at all.
2. Late Treatment (May): If you wait until May, that same chickweed plant could be much larger, have flowered, and be producing hundreds, or even thousands, of seeds.

Therefore, later in the season, and into the next year the seedbank is significantly reduced by treating plants earlier. 

By Year 3 you have greatly reduced the weedburden through 2 strategies... Reducing the growing medium and reducing the seedbank. Therefore your regrowth will be substantially less. 

What else can be done to reduce ongoing costs?

With less weeds growing, there is less adding to the soil build up, so this will naturally reduce, but you now understand that the detritus and seeds from adjacent spaces are contributing to your problems. By this time, you have freed up a little time and recouperated a little from the capital expense in the first year, so you decide to replace some of the adjacent areas with slower growing plants which have less leaf fall and are less likely to drop seeds into the area you are keeping free of weeds. 

This will almost eliminate the amount of soil you have to deal with and reduce the seedbank affecting the area - so your weedburden is going to be through the floor. This means less time sweeping and weedbrushing, less weeding intervention and less cost. 

What other benefits does this approach to weed management yield?

Beyond cost savings, IWM offers numerous benefits:

1. Reduced Freeze-Thaw Damage: Less detritus means less damage to surfaces from freeze-thaw cycles, reducing resurfacing costs.
2. Improved Drainage: Fewer blockages reduce flooding and drainage maintenance costs.
3. Enhanced Accessibility: Clearer paths improve mobility.
4. Improved Water and Air Quality: Reduced pesticide runoff and removal of heavy metal particles.
5. Enhanced Aesthetics: Tidier spaces can attract more public spending.

Conclusion: IWM – A Sustainable Investment

IWM is not just about short-term weed control; it's a long-term investment. By addressing the root causes of weed problems, IWM creates a sustainable and economically viable approach. While initial investment may be required, the compounding benefits and reduced long-term costs make IWM a financially sound and environmentally responsible decision for the council. It offers a far more effective and ultimately cheaper approach than simply reducing glyphosate applications without addressing the underlying causes of weed growth.