Minnesota Farmer


From drought to flood
May 8, 2012, 2:33 pm
Filed under: Farm, Minnesota, rain, tillage, weather | Tags: , , , , , , , ,

Our area of southwestern Minnesota has been in a drought since last July.  We have gone months since we had a “normal” rainfall amount.  That has changed.  In the last few days we have nearly erased the moisture shortage, and it has caused another problem, erosion.  In just a few days we had almost 6 inches of rainfall, one event had over 2 inches fall in one hour time.  This is something that tilled farmland cannot handle.

Many fields have water standing in them.  This water ponding came about because the soil could not absorb water in such vast amounts falling so fast.  Even grassland will have water run-off when huge amounts of water fall.  This water then ponds in lower areas to slowly filter into the earth.  Some of this water will go directly into streams and lakes, but most of the water never gets there.  It is held to either recharge the soil water table, or evaporates back into the air.

When you get this much water it will move exposed soil.  In the case of the picture above the soil moved only a few feet.  Most soil erosion is deposited near to where it erodes from.  High areas are torn down and low areas built up.  Areas that erode near streams and lakes will be deposited into the water, but most soil does not move that far.

In some cases the erosion can be both wide and deep, it can tear out even mature crops, a newly planted crop has no chance.  Most areas that are prone to this type of erosion have been converted into grass by farmers.  When there are long periods of light rain and no erosion farm folks start to forget what happens in a large rain.  When these events happen, they remember again, and grassed water ways are planted.  Unfortunately periods of drought tend to cause more erosion, since soil that is dry is easier to move than wet soil.

Roads also suffer when rain falls in large amounts.  Here water could not get through the culverts under the road fast enough and it topped the road and removed the gravel.

Roadway culverts do help to meter out the water.  They will hold it back so only the largest rainfall events cause problems.  The ponded water behind a roadway gives soil a chance to settle out and not make it to a stream or lake.

We can still use more rain to keep our crops growing, we just need it to fall slowly and in smaller amounts until our crops are bigger.

Michael

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1 Comment so far
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Interesting. One extreme to another. Would be nice if it was consistent.

Comment by My Perfect Weather




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