What gets burnt
A cane crop leaves a large quantity of dry leaf trash at harvest. Burning it clears the field in an afternoon and destroys organic matter, nitrogen and sulphur, kills the surface soil biology, and returns only a small amount of potassium in the ash.
What trash mulching does instead
Spread the trash in alternate inter-rows, or across the field in the ratoon:
- Conserves moisture substantially through the hot months — often the difference of an irrigation or two.
- Suppresses weeds, which in a wide-spaced, slow-starting ratoon is a large saving.
- Moderates soil temperature, keeping roots working through heat.
- Adds organic carbon as it breaks down, which is the one thing cane soils under continuous cropping are most short of.
- Reduces erosion and crusting.
Doing it properly
Spread it, do not heap it. Even coverage between the rows, not a ridge on top of the stubble.
Add a decomposer culture where moisture allows, which speeds breakdown considerably. Dry trash sprayed with a culture and left dry does nothing.
Add a little nitrogen with the trash. High-carbon material immobilises nitrogen while it decomposes, and the ratoon can look pale for a few weeks if you skip this. That temporary paleness is the commonest reason growers abandon the practice, and it is entirely preventable.
Keep it clear of the stubble line where you are applying fertiliser or where sprouting needs light and warmth in a cool ratoon.
Where it does not suit
- Waterlogged fields, where you want the surface to dry.
- Fields with a serious rodent problem, since trash gives cover.
- Where the trash is genuinely worth more as fodder. That is a real trade-off and fodder often wins; it is a calculation, not an assumption.
The ratoon connection
A trash-mulched ratoon sprouts better, holds moisture better and needs less weeding than a burnt one. Since ratoon crops are where cane profitability is made or lost, that is the place it pays most.
Burning crop residue is restricted in many states. That is a poor reason to stop, and it is a reason.
