Minnesota Farmer

Green effect

Are the farming practices of today actually lowering temperatures?  That is the question that came up at a recent marketing meeting as we considered the prospects for yields this summer in the face of dry conditions in Southwestern Minnesota.

It’s a known fact that asphalt, concrete and roofs are raising the temperatures in our cities.  There has been an effort made to add green plants to the roofs of our country.  Green spaces and trees are encouraged in parking areas and along city streets.  These efforts are as yet making little headway in the heat dome associated with large cities.  Could the reverse be working in farm country?

We were told that the last time Southwestern Minnesota had a 100 degree day was back in 1983.  I remember from my childhood that 100 degree days were possible, but not abundant.  Still no summer was complete without a few.  Today the carpet of green in corn and soybean country is something that is new in the modern era.  For the 100 degree days to go away in the face of increasing global temperature, something must be happening.

When the pioneers came to this area the hills were covered with the green of the prairie.  The lush green of spring and summer always gave way to a dustier grey green and then tan and brown as the year went on and spring rains decreased.  Late summer temperatures could build up as the browns of autumn allowed the earth to hold heat.

Then the farmer broke the prairie and planted mostly wheat and oats.  These crops, like the prairie grass before them used the rains of spring and summer and then were harvested leaving fields either black or brown from late summer into the winter.  Farmers needed the wheat for a cash crop and the oats to feed their horses.  Corn was rare here although present, wheat gave a better yield.  Livestock was still a major part of the landscape and pastures were needed to feed a few cows and the horses.

As corn yields increased, wheat became less popular as a cash crop.  Corn had previously been a crop for human consumption, now it fed an increasing number of chickens and pigs, both animals that thrived on seeds.  As modern machinery moved in, we learned how to chop up and store the whole corn plant making it feasible to use as a winter feed source for cattle.  The production of young cattle moved to river valleys and western, drier areas where cultivated crops had a hard time growing.  To ready cattle for market, they were moved to corn country, or the corn was moved to them.

A major change in technology, the tractor, made further changes in the way farming was done.  16,000 plants per acre was an incredible population in corn fields of my youth.  There was no way to keep the weeds out of the field short of manual labor, and many corn rows were still planted far enough apart so you could get a horse between the rows, 38 to 40 inches.

With todays modern machinery, the use of herbicides to reduce weed competition and careful use of fertilizer, farmers are planting over 30,000 corn plants per acre in 30 inch, 22 inch or even 20 inch rows.  Even soybeans are planted in narrower rows, between 7 and 15 inches, to shade the dirt between the rows and hold the moisture and keep weeds down.  Both corn and soybeans stay green longer into the fall than did wheat and oats, thus reflecting heat that otherwise would reach the ground.  The result is a steamy jungle in the fields.  The plants are drawing moisture from the soil and “sweating” it out.  This moisture seems to be holding down daytime highs and raising night time lows.

To show you what difference green plants can make, just look to our deserts.  With no plants to cover the ground, daytime temperatures can soar over 110 degrees, even in northern deserts.  At night temperatures drop dramatically, sometimes approaching freezing.  Add green as in our forests, and daytime temperatures are decreased and night time temperatures increased.  One of the major factors used to slow desert growth is the introduction of trees.  It has been proven that deserts increase where trees are removed.

So are todays farming practice actually lowering temperatures?  It sound possible.  Perhaps we can look to farmers, ranchers and foresters to help us hold off global warming.



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