Key Points
- Anticipated high slug pressure this autumn is exacerbated by leaving crop residues on the soil surface.
- Large amounts of stubble and trash will also compromise residual herbicide efficacy and mineralise soil nitrogen.
- Encouraging soil biology to break down crop residues with tailored inputs like L-CBF BOOST can have a valuable impact on crop establishment.
- Further interdictions, such as light cultivations and pre-emergence applications when the soil temperatures are warmer, will speed up this process.

The quick breakdown of crop residues is critical to maximising the crop nutrition benefits of chopped straw and stubble whilst mitigating increased slug pressure and crop establishment challenges that come with it, says David Maxwell of QLF Agronomy.
The Certis Belchim SlugWatch forecast predicts moderate activity through the middle of October, which could be further increased depending on the specific field conditions. Crop residues will increase slug pressure by providing wet organic matter to feed and breed on the soil surface.
Further to the overall slug population increase, cereal straw’s high carbon-to-nitrogen ratio (80:1) heightens the slug threat to growing crops by creating an environment that encourages slugs to feed on low carbon-to-nitrogen crops rather than the residues.
In addition, according to AHDB calculations, an average wheat crop leaves around 9 t/ha of dry matter behind in the straw, chaff and stubble. With each tonne of straw containing 5kg of nitrogen, 1kg of phosphate and 9kg of potash, considerable nutrient value is locked up for the next crop.

How can we speed up the breakdown of previous crop residues?
Soil microorganisms are the primary mechanism for breaking down crop residues. Light cultivations that incorporate it into the soil will aid this process, as will the addition of nutrition to encourage microorganism populations.
That is where L-CBF BOOST helps. It is derived from molasses, a complex mix of available carbon, yeasts and other microbial growth factors. QLF Agronomy processes the raw material to ensure it is compatible with modern spray equipment and formulates it with liquid nitrogen to produce the finished product.
L-CBF BOOST delivers an ideal 24:1 carbon-to-nitrogen ratio – the perfect microbe food, says David Maxwell.
“Using 10 L/ha of L-CBF BOOST sweetens chaff, stubble, and chopped straw, making it more palatable for the soil’s biology to digest, especially in the presence of microbial inhibitors like late fungicides sprayed on the crop in June.”
“It can be used pre and post-emergence. However, I prefer pre-emergence because it has longer to act, and warmer soil temperatures will further encourage microbial activity.”
For farmers operating a direct drilling system, David says they may want to consider light cultivation to reduce the amount of stubble on the soil surface. This will provide further benefits for slug control and residual herbicide activity.
Applying L-CBF BOOST also benefits early plant vigour also because of the increase in available nutrients, especially nitrogen. David highlights a QLF Agronomy trial in the US (Graph 1), repeated over two years, that showed a 368% increase in soluble nitrogen and an 11% increase in crop residue decomposition from applying L-CBF BOOST on grain maize stubble.

Graph 1: Arise Research, 2016, residue decomposition trial. Improvements in residue recycling and total nitrogen availability were observed.