Element Number Three: Irrigation
A downside to growing in greenhouses and high tunnels is that you have to have access to water and a way to irrigate these crops. That can be a positive, as it motivates you to build a system that you can use for your field crops as well. Even in the eastern U.S. where we farm, our irrigation is used every year. Rainfall seldom comes exactly when you need it, and having a way to irrigate your crops is the difference between being subject to droughts and being able to produce a crop every single year.
For a small greenhouse and high tunnel, you can, for the most part, just run a garden hose from whatever water source you use for your house. If you are dependent on a public water supply, it is a good idea to have a backup system for truly sustainable growing, independent of whatever is happening in the public municipalities. The easiest, and relatively cost-effective, system is to just catch runoff water from whatever buildings you have on your property. If you are in the desert southwest, you may not get enough rainfall to make this work, but even a small rainfall event can produce a pretty good volume of water.
A simple system that we find effective is to use food-grade IBC water containers. These are the big square water tanks with a metal frame around them. They normally have a capacity of 275 gallons, and depending on where you live are relatively inexpensive. I purchased several that had once held artificial flavorings for $40 each. The great thing is that they already have an opening at the top and a water valve at the bottom. This makes them perfect for collecting roof runoff from a gutter with a simple reducing valve. If you elevate them a few feet off the ground, then you’ve got a perfect gravity-fed irrigation system. There is generally enough head to supply a small drip irrigation system if you use low-pressure irrigation tape, which functions fine at less that 7 psi or so. You can always raise the tank or connect multiple tanks to create a larger capacity or more head (equals more pressure). Make sure you set the tank on a good solid base, as these tanks will weigh over 2200 pounds when full. We buy our irrigation supplies locally, as all the material we’ve discussed comes on large, heavy rolls. If you don’t have a local source, Drip Works (www.dripworks.com) out of California is a good mail-order source that has everything you need.
We collect water from our barn roof and even have our high tunnel guttered, which gives us a huge capacity to fill our water tanks. You can even collect water from your greenhouse, which is one reason I like wood framed greenhouses; they are easier to gutter! We have a public water supply, but it is comforting to have the capacity to water many of our crops right from our own property. Strategically placing your garden or growing beds close enough to your gravity-fed water source is an important consideration that will pay you back sooner rather than later.
These tanks are clear, so they will allow algae to grow, which can clog up your drip tape. You can paint these tanks or cover them to prevent algae from growing, but we’ve found that we use the water fast enough that it isn’t a problem. If algae starts to grow, then just empty the tank. You can also get some algae-eating fish and put them inside. We keep goldfish in any uncovered rain catchment to keep mosquito larvae down. Our goldfish survive the winter in the tanks, which suggests a more advanced aquaponics system, which we haven’t tried yet but is a great option for raising protein and liquid plant fertilizer.
If you want to pressurize your system and add the potential for pumps, filters, et cetera, then make sure you’ve got an off-the-grid system that is able to provide that. The time when you’ll need it the most is when it won’t be available, so make it happen now.
Element Number Four: Plastic Mulch
You’ll also need an irrigation system for this next element—plastic mulch. A product that most commercial growers use, but for some reason hasn’t been widely adopted by the backyard gardener, is plastic mulch film. There is a lot of back and forth in the organic/sustainable growing community about the use of plastics in agriculture. Technically, since plastics aren’t all that sustainable long-term many people avoid them. But if the benefits are so great, why not use them while you can? Everybody I know still drives around using fossil fuel and plastics are a part of life. Even battery powered car folks use fossil fuels, as 99% of our electricity in our area is derived from either coal or natural gas. They don’t like to be told they have a coal-powered car, so I just grin and keep my mouth shut! Plastic mulch is just a thin 1-mil film that you lay over your planting bed and plant into. It is a weed barrier as well as a season extender, as it warms the soil, allowing you to plant much earlier and obtain higher yields with less pesticide use. It is a win-win. The fossil fuel you save on tillage and pesticides probably equals what goes into the plastic. Even if it didn’t, it is worth the benefits you get. Plastic mulch is generally black, but comes in other colors for different purposes. For instance, red-colored mulch gives you a supposed 20% yield increase in crops like tomatoes, but it also costs about 20% more than the black, so for the most part it’s not worth it unless you absolutely need the highest yields from the smallest area. Silver or white mulch reflects some heat and can be used in the hottest climates, and gives some insect deterrence. Since this plastic is impermeable to water, you have to lay down drip irrigation tape under the plastic in order to water your plants.
While commercial growers lay this with a machine, it is easy to do by hand. We lay it all by hand in our high tunnels. You just unroll a piece or two of irrigation tape on your growing bed where your plants will be. The edges of the plastic are buried with a shovel or hoe as you go along, which seals the mulch and keeps it from blowing up. This is a process that can be done alone, but iit is easier with a helper or two.
You transplant tomatoes, peppers, eggplants, melons, et cetera directly into the mulch with a sharp hand tool to cut through the plastic. The plastic keeps the produce cleaner, decreasing soil-borne disease and allowing greater yields. Just make sure you water enough, as the only water that makes it under the plastic is what you put there, so you have to check moisture levels frequently. It also works well for potatoes and sweet potatoes, which are harvested by pulling up the plants and plastic, which is done at the end of the season anyway.
If you are careful you can double-crop on this mulch. For instance, we’ll plant early squash on a fresh bed, and when the squash is done in mid-summer we direct seed plant green beans for a fall crop. The extended season and quick growth you get using this mulch makes it possible. At the end of the season you can pull it up and dispose of it or recycle it. There are even organic-approved biodegradable mulch films made from corn starch that you can just till in when you are finished. They are quite a bit more expensive, but as the price comes down they’ll be a useful option for many.
The areas between the rows can be carefully tilled, or mulched with straw or some other material to keep down weeds. For this space we often use another groundcover most often called landscape fabric that is a heavier, woven material. This material is often used as permanent mulch as it lets water through and will last for several years. We use it for applications like this by unrolling it and fixing it to the ground with landscape staples. At the end of the season we roll it back up and store it out of direct light; this process allows us to use it year after year. You can use bleach to disinfect it between crops, if you wish.
Either of these materials can last indefinitely if you store them out of the sun, so it is worth putting a few rolls on the shelf. These products are worth learning how to use for the gardener who wants the best yields in the smallest area with the least amount of work. A few rolls stored up will increase your growing potential and survival potential greatly. While we can and do use organic, all-natural growing techniques on a commercial scale, you may have to boost production substantially, and these materials can help you do just that.