Tuesday, May 21, 2013

Spring On The Farm: Black Plastic Mulch and Drip Irrigation


Agriculture is inherently an unnatural process.  It is a division of horticulture, the study of the cultivation of plants.  It's unlikely to find plants naturally growing in perfect, weed-free, straight lines.  Wild plants do not sprout up in raised soil beds year after year.  Human selection has perpetuated and "improved" the development of our food system to feed large populations of people throughout the world.  Since agriculture is not a direct act of nature, it requires outside interaction and when humans get involved, choices have to be made.  As we continue to develop a deeper understanding of the current limiting factors we face i.e. natural resources, we have to decide how to properly manage our means of sustenance.  This includes a balance of environmental, economic and social factors.  

Today we are looking at black plastic mulch and drip irrigation, a great combination involving a balance of time efficiency and environmental...

impact.  Although a solution, the positives and negatives of this choice, as with most in life, lies in the eye of the beholder.

The basic advantages of laying black plastic mulch are...

1.  Dark color absorbs heat from the sunlight adding extra warmth to the base of the plants.
2.  It suppresses weed growth by preventing sunlight from reaching weed seeds in the soil bed.
3.  Helps the soil retain more moisture by inhibiting evaporation by direct sunlight contact.
4.  Maintains the placement of the drip irrigation line.
5.  You can use a tractor to streamline the process, saving labor hours and reducing wear and tear on the body.

While these are all strong benefits, there are many who take issue with the environmental impact of using so much plastic every year.  The plastic gets beaten up, so it is rarely salvageable for a second season.  On large fields or in large quantities, this amount of plastic can add up.  

With about 2,000 pepper plants to transplant and many other acres to cultivate this summer, spending days on end weeding is not an option when it can be avoided.  Peppers are heat-loving crops so they prosper in the added warmth from the black plastic and drip irrigation lines help massively reduce the amount of water needed throughout the season.   

To get started, we first analyze the field and determine which direction our soil beds will be made.

Once the plan is set, the tractor is brought in

and on it, the mulch layer/drip irrigation implement.  By clicking the picture below you can see the roll of drip irrigation tape that is set above the roll of black plastic mulch.  This roll of irrigation is fed through a pipe that buries the irrigation tape to a depth you set depending on your crop needs.  You can also set the irrigation line to fall to the right, left or center.

Get to know your implements.  Since the team I was working with is familiar with this mulch-laying process, they informed me that it's best to start about 8 feet prior to the start of the planting space.  This short distance provides enough time for the depth for the drip irrigation to be buried (~2'' in this case) and for the bed shaper to create a smooth and even bed covered by a tight black plastic mulch layer.

Taking a closer look shows that there is a lot of interesting ingenuity going on here. The black plastic roll is sent through a series of rollers to ensure it comes out smoothly.  The rubber tires press the plastic into the edges of the bed and the symbol-like bed shaping discs cut into the soil, burying the plastic mulch and creating a beautiful, even raised bed.   The two inner guards prevent soil from getting onto the planting area of the plastic mulch.

Here's a quick video of the action, watch it in real time: 

When everything is in position, one person holds the irrigation line and stands on the end of the black plastic, as pictured below, to create some tension and prevent the everything from dragging.  A thumbs up signals it's time to head straight down the bed (Note: A couple shovelfuls of soil can replace the man with the funny hat, but that's up to you).

After some minor tweaks to ensure the bed is exactly how you want it, it's just a matter of setting up at each end and driving straight.

We flew through this acre in just a few hours.

A nice addition, is this bed marker, which provides a mark in the soil for the center of the next bed.  This line is where the tractor driver lines up the center of the tractor with each pass.  It's adjustable arm allows you to create as much distance between beds as needed.

Straight, organized and weed free a little hard work early in the year, makes life that much easier later on.

So all this plastic has to get tossed at the end of the season, but there are alternatives such as BioTelo biodegradable mulch, but as you may have guessed, this material is much less sturdy and can start to decompose right on the field, making it much more difficult to remove at the end of the season.  If left in the field, it could take longer to decompose completely before you need to start working that soil again.  This can cause problems by gumming up your tractor and making it tougher to work the soil for your next round of crops.  These are all just possibilities, some people find it works great.  

These are great innovations and interesting steps in the direction of more manageable, safe, efficient agriculture.  There are a lot of limiting factors when dealing with nature based systems, so it is always fascinating to learn about the engineering and technology that has been developed to help solve this ever evolving puzzle.


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