Recent mild
temperatures and rain has melted snow cover across central and southern Russia
and eastern Ukraine.
As temperatures returned
to more seasonal averages this week the melt water, which had pooled and failed to
drain through the frozen soil, turned to ice.
Several issues going
on here that are worth noting.
Rain on snow is not
a good thing, it speeds up thawing but it also collapses the structure reducing
air spaces between ice crystals which is what gives snow its insulating
property. A bit like very old loft
insulation that has lost its integrity and is now half the thicknesses it was when
it went in twenty years ago.
There is still plenty of snow on the ground but it is thin and less protective should temperatures drop further although more snow is forecast later this week.
Then there is ice
which has the real capacity to do some damage.
Melt water and rain
collected into low lying depressions and was unable to drain through frozen
soil before temperatures dropped and it turned into ice.
Where snow has
melted completely the ice is obvious but we also are finding ice when we dig through the snow.
Ice that has
formed beneath the snow is, perversely, insulated from any rise in temperature
and in all probability will be around now until the snow thaws sometime in
March.
Ice has a high
thermal conductivity and will amplify the effect of low temperature so it doesn’t
have to get really cold to start doing some damage. It also has low gas permeability
and, in extreme cases, will smother or suffocate plants by depriving them of oxygen
(Poltarev et al., 1992).
Or to put it another
way, plants in which are now encased in ice will start to die very soon.
It’s difficult to
put the level of risk in to context given that much of the problem is hidden under snow
and it is difficult to get out into fields at this time of the year but if pushed we are seeing issues
on 10-20% of the fields we visited and across Moscow, Lipetsk, Oryol, Voronezh, Kursk and Belgorod.
At this time we don’t
have verifiable information for Ukraine but based on what see near the Russian
Ukraine border and anecdotal evidence suggest there is a similar issue in eastern
Ukraine.
We won’t be able to fully
assess the extent of any damage and yield implications until will carry out our
independent Post-Winter Crop Tour of Russia and Ukraine scheduled for late
March, subscription details to follow soon.
(Check my Twitter feed for more pictures)