Wednesday, June 9, 2010

Racing to Conserve on Artificially Drained Land

I love the Indy 500. I’m a born and bred Hoosier with a hankerin’ for racin’ and a need for speed, ! I probably haven’t missed the Greatest Spectacle in Racing for over 15 years and every year it still amazes how fast those cars make it around that 2.5 mile track. This need for speed is a common trait among many people and it seems to creep into almost all facets of life; sometimes that’s good and sometimes not so much!

For example, good - fast food, eating your lunch 30 seconds after you order it …….. not good - fast food can taste like it was prepared in under 30 seconds; good – roundabouts, help traffic move more efficiently and reduce 4 way stop delays…… not good…….have you seen the movie European Vacation?(“look kids, Big Ben… Parliament”).

For agricultural example, good – bigger/faster tractors can get across the fields quicker, pull larger equipment, and potentially spread out compaction with distributed weight over larger tires/tracks……not good – corn planted too fast can make the planter bounce and leave a very inconsistent stand which means a likely reduced yield.

As for this blog entry’s specific ag/conservation example, good – agricultural drainage, gets the excess wetness out of the farm fields quick and in Indiana, and much of the Midwest, this is absolutely critical to crop production on most of our farm ground and without it we would not enjoy the strong agricultural presence that we do today…. not so good, altering the natural drainage patterns, water tables, etc. can speed the transport of pollutants to surface waters as well as some other environmental concerns that this modified drainage can exacerbate.

Let’s trench in to this agricultural drainage topic some more, what’s the story??

Much of Indiana’s ag land is drained with ditches or an extensive subsurface drainage system, otherwise known as tile, and many times a combination of both. Without this drainage network, which quickly sends rainwater and excessive moisture from the soils downstream, many of our fields would be too wet to farm or would grow poor stands of crops. So, over the last century or so farmers have invested in these systems to improve their efficiency, boost yields and continue to feed the world’s growing population.

The unfortunate side of these improved drainage systems, as with most anything with nature, there are and have been lots of adverse effects to the aquatic ecosystem that come from moving the water away from the fields quickly. Here are just a few of the general effects associated with increased drainage:

1. Excess nitrogen being transported to surface waters. Nitrogen, which is applied to cropland and is essential for plants, is very water soluble and easily leaches down through the soil to the subsurface drains. Once in the subsurface drain, nitrogen is then quickly transported to the nearest surface water/stream/lake. Excess nitrogen in surface water can significantly boost algae growth or a bloom. Once the algae use up that nitrogen they begin to die off and decompose which uses up the dissolved oxygen in the water. The dissolved oxygen can drop to a point that the area is no longer viable for many aquatic organisms. This lack of oxygen is commonly referred to as Hypoxia. Hypoxia in the Gulf of Mexico at the mouth of the Mississippi River is a well-documented concern.

2. Potential for increased flooding. The rainwater that once used to be soaked up by the land or temporarily pond on the surface for days before slowly moving towards the nearest stream, now it gets there much quicker through tile and ditches. The altered drainage of tiles and ditches send higher quantities of water in a shorter interval of time downstream directly following rain events versus the natural groundwater or landscape delivery which will bring water downstream in a more gradual manner comparatively. This can depend heavily on soil infiltration rates, water holding capacity, ground cover, and many other factors.

3. Erosion on ditchbanks. Ditches tend to be dug in a trapezoidal fashion in a profile view which is an extremely efficient design for moving water quickly. However this design historically requires a great deal of maintenance due to the undercutting of the banks from erosion and then sedimentation downstream. Water systems naturally develop stability through the development of floodplains which act as a relief valve if the waters get too high. In a ditched system, the water is meant to be contained within the ditch, and therefore in high volumes the water will tend to cut a deeper channel which brings instability to the whole setup.

Here’s where the agricultural conservation folks come in hopefully with some usable solutions that are currently being utilized and studied for their effectiveness: Two-Stage Ditch, Drainage Water Management, Constructed Wetlands, Denitrifying Bioreactors, and Blind Tile Inlets. Please check out the next Chew On Dirt to learn more about these practices which are aimed to minimize these environmental concerns associated with drainage.

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