There are definite downsides to keeping wheat / oat / barley straw on a field
after the grain
has been extracted. One is that if there has been any infection by specific
pathogenic rust
fungi, the life-cycle can be completed through some of the various life forms
ready to attack
the next crop with a vengeance. Tina showed us photos of a kind of species
fungus that
attacks the juniper trees native to her locality. Wheat rusts are not as
spectacular, but are
more deadly to the (wheat) host. NZ cropping farmers usually set fire to the
residual straw to
deal to that problem. Spectacular mushroom clouds of smoke as these controlled
burns take
place.
This reduces the need to use chemicals to control the rust fungus.
Secondly, ploughing the straw under brings a real nutrient problem for the next
crop. The
bacteria which do the decaying of the cellulose straw stems need a LOT of
nitrogen if they
are to do it, and they will absorb any / all nitrogen available in the soil
adjacent, in order to do
the process.
Without specific recognition and action on this score, the next crop can be
very
nitrogen-deficient.. Same applies to corn "straw". Nearly pure cellulose.
However, having read in these pages how much some intensive cropping land
around where
some of you live (Mid-west?) has a vile smell, maybe adding heaps of fertiliser
doesn't bother
some farmers too much ...
Brian Swale
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