In article , Michael Percy wrote:
Phred wrote:

One assumes that, given time and the build up of *soil* organic matter
as a result of the trash blankets gradually rotting down, some sort of
equilibrium may be established WRT N availability to the crop.
(Maybe this has already been shown (or not -- I'm not all that
familiar with sugar cane agronomy.)

If organic matter without mixdown is accumulating in the soil profile, it
must be a very? slow process. You produce, meaning you get nitrogen down
there somehow, while building om up slowly, then om in profile must shift
towards the recalcetrend. Not worth waitng for, would be my take, find
better ways to bring in the N. If it is really the best to leave the trash.

Yeah. My thoughts too, hence the "given time". However, given that
(time), there must be some increase in soil OM as a result of trash
blankets. After all, the things usually lie around after each harvest
through several ratoons. Admittedly, most of the litter will probably
simply "evaporate" into water and CO2, but bugs and worms must achieve
something compared with life before green cane harvesting when the
whole lot was just burnt each year. (Now it's usually only burnt
before planting a new crop AFAIK.)

Sounds nice but might be more efficient to feed it to animals. Just my 2p
and I do not know a whit of sugarcane agronomy.

I was going to respond last night, but at 2 a.m. I decided it could
wait. A timely procrastination as it turned out as there was some
discussion of this issue in the news here today, concerning an aspect
I would have overlooked.

The first point is that since the days of draught animals are long
gone, most cane farms around here no longer have fences. In some
districts, and in certain particular situations (e.g. a significant
area of non-arable land [usually due to excessive slope] which was
cleared before world heritage "pristine" rainforest intervened),
there are mixed farms of cane/beef cattle. The cattle typically graze
on exotic pasture grasses, often naturalised rather than sown for the
purpose. _Panicum maximum_ and _Brachiaria_ species dominate (with a
fair admixture of the weedy blady grass (_Imperata cylindrica_) in
most cases .

The second point, which was raised today, is that cane farms were
heavily contaminated by chlorinated hydrocarbons over several decades
in the form of insecticide applied to control the larvae of the cane
beetle. With modern concern and consequent controls over potential
contamination of meat products, cane farmers don't feed crop residues
to cattle.

Given the current serious drought affecting most of eastern Australia,
there have been suggestions for using cane trash as drought feed.
However, for the reason given above, people are being very cautious
about it. Although BHC etc. have not been used now for quite a long
time, these compounds do persist in the environment for a very long
time.

So, before anyone would feel comfortable feeding cane crop residues to
stock, there would need to be some fairly careful testing of material
from individual paddocks. It may not be practical... but it will be
interesting to see how things do pan out if things get desperate.


Cheers, Phred.

--
LID