HYDROPONICS VS. SOIL

Wheatgrass Grown in Coco Coir

I’d like to take a moment to address the issue of hydroponics and, why, after 10 years of growing wheatgrass in soil, I have finally given in to the idea that hydroponics is not only a viable alternative but actually a smarter one for some growers, with no loss of product quality.  I will agree that hydroponics has taken a bad rap over the years for producing less tasty, more watery fruits and vegetables, but that was when commercial hydroponics was in its infancy, and growers were essentially just experimenting.  In more recent years, however, it has become clear that hydroponic growers are mastering their craft and producing fruits and vegetables that have surpassed the taste and quality of some of their soil-grown competitors.  I now confess to choosing a particular type of tomato, basil, and salad green over all others at the grocery store, and (with great surprise!) they are all grown hydroponically.   That got me to thinking.  If these growers can produce such outstanding  tomatoes, basil, and lettuce, couldn’t I produce an outstanding hydroponic wheatgrass? 

While I am a strong proponent of soil-grown, it has caused me a fair number of infrastructure problems in my growing operation throughout the years.  Soil definitely has its place, outdoors and in greenhouses, but for an indoor growing operation—in my case, a 300 square foot year-round, climate-controlled growing room akin to a laboratory setting—it wreaks havoc and has caused me innumerable problems in the way of soilborne pathogens, dust, odors, storage limitations, and physical injury.  Even when one works as cleanly as possible, soil has a way of taxing indoor air cleaning systems, which can turn into hundreds and even thousands of dollars in maintenance costs when the system unexpectedly and prematurely fails because of fine dust buildup.

During the years when I was growing primarily in soil, I was also experimenting with soilless media for my floral wheatgrass crops.  Call me crazy, but I just didn’t like the idea of putting soil on a fancy dinner table for the above-mentioned reasons:  pathogens, dust, odors.  Also, soil wasn’t the easiest thing for florists to work with when they needed to cut pieces to fit their decorating needs.  So I began growing in coco coir (ground coconut husks), which turned out to be an exceptional growing medium.  The simple fact that it is not soil is what makes it a hydroponic growing medium, and thus began my journey as a hydroponic grower.  Coco coir looked and acted just like soil, only it was pathogen-free, retained water longer and more evenly, didn’t cast odors, and didn’t present the mold problems that soil seemed to present at times.  Because it was packaged in dry compressed bricks, it was lighter than soil, took up less storage space, and eliminated the issue of frozen soil in winter.  My only problem with coco coir was its nutritional value.  Sure, it produced a nice looking short grass for floral use, but could it possibly provide the same nutritional benefits as soil for my juicing clients?  If not, what did I need to do to bring this growing medium to a place where I could feel good about selling what I was growing to customers who valued product nutrition above all else?

First of all, let’s look at the nutritional needs of the wheat berry as it sprouts, produces shoots, and becomes the grass that is eventually harvested.  Seeds generally do not require any nutritional amendments when they are just sprouting.  That is true of wheat berries as much as it is true of any other seed.  The nutrition a seed requires to sprout into a baby green essentially comes from the seed itself.  It’s when a plant’s second set of leaves begin to emerge that it depends on its growing medium as a lifeline.  At that point, all conscientious growers, whether they grow in soil, coco coir, water, or anything else, take measures to ensure that their growing medium is equipped to support the nutritional requirements of the plant. 

 

After a great deal of experimentation, I have found that wheatgrass does fine in coco coir up until it is time to harvest  and pretty much not a moment more.  Sure, the entire tray doesn’t yellow all at once because not every single wheat berry sprouts at exactly the same time, but the moment each little shoot begins to require more nutrition for its next level of maturity (when the grass begins to form another blade), it no longer has what it needs to thrive in coco coir alone and begins to yellow, much more dramatically than when the grass is grown in soil.  This predictable yellowing tells me that I am working with some sort of nutritional deficiency in the growing medium and that nutritional supplementation is required. 

 

So, let us look at what types of nutrients coco coir has to offer, what types of nutrients wheat requires, and what our options are in terms of healthy organic supplemention to help get us to where we need to be on a nutritional level and feel good about our hydroponically-grown grass in a way that we have come to feel good about our soil-grown grass.

pH.  First and foremost, let’s look at pH.  Exceedingly important to keep that right.  Without the proper soil/water pH, everything else goes out the window.  Wheat grows best at a pH between 6.0 and 7.0, which is slightly acid.  I have personally found that it grows best somewhere around 6.5.  As mentioned in one of my previous articles, the slight soil acidity enables the plant to process all of the required micro and macronutrients most efficiently.  I realize that is tough concept to swallow for some folks who are looking to alkalize their bodies using wheatgrass, but trust me on this one:  soil alkalinity does not equal body alkalinity.  At least not here.  So if you are growing in soil, this means testing your soil supply periodically with a soil testing kit, and also testing your water with the proper metering device to make sure that you are not flooding your wheatgrass everyday with something that is either too acid or alkaline for your grass. 

 

Coco coir itself does not need to be measured with a soil tester.  Its pH is pretty stable at the correct level, between 6.0 and 6.5 straight out of the bag.  It’s when you add that 7:1 ratio of water to your coco coir that everything has the potential to change, so having a meter that measures water pH is extremely important for hydroponic growers as well.  I cannot stress that enough.  My water tends to be very alkaline, close to 8.0, so I add a little bit of citric acid to my water bath before soaking the coco coir.  It only takes a tiny bit to dramatically change the water pH.  Citric acid is naturally derived from citrus fruits and provides a short-term correction to an alkaline growing medium.  For a short-term crop like wheatgrass, citric acid works perfectly. 

Macronutrients.  Next, let’s look at the macronutrients.  All plants need Nitrogen (N), Phosphorus (P), and Potassium (K) to survive, each in varying quantities depending on the plant.  For wheat, higher levels of Potassium are desired by farmers for higher protein content in the grain, but that potassium uptake is not even a factor until the heading stage, and it is irrelevant for the purposes of harvesting wheatgrass.  Because wheatgrass is harvested as a baby green, technically halfway through its first stage of growth, it does not require heavy fertilization.  Suffice it to say, unless your soil is entirely deficient in one of the three macronutrients, your wheatgrass should be just fine, but the only way to know exactly what you are working with is with a soil testing kit.  A simple soil testing kit to tell you if your NPK ranges are high, medium or low is all you really need as a home grower.  A low reading on any of the three macronutrients calls for some sort of soil amendment to bring things into balance (see Simple Soil Chemistry and Organic Amendments for Your Wheatgrass Crop).

 

Coco coir, on the other hand, is a given.  It is naturally high in Potassium, with lower levels of Nitrogen and Phosphorous, which means that the type of natural amendment we are looking for is one that provides Nitrogen (to help give a plant its proper green) and Phosphorous (for strong young root growth) but not as much Potassium (which, in excess, can actually inhibit nitrogen levels).  What I have found to work best for my needs is the addition of spent coffee grounds to my coco coir mix, which gives a nice Nitrogen boost (solving the problem of yellow grass) and helps increase Phosphorous for strong root growth without also increasing Potassium too much.  With the coco coir, I like to keep my amendments plant-based as this presents more immediately bioavailable nutrition for the roots of my short-term crop.  Coffee grounds do not seem to present composting issues that can damage a baby crop, and contrary to popular belief, spent coffee grounds are not high in acid.  The pH of spent coffee grounds measures with some variability in the 6.0 range, which is exactly where we want to be with wheatgrass.  If you choose to use spent coffee grounds, be sure to refrigerate them until use.

Micronutrients.  Coco coir, while not a micronutrient powerhouse, actually does carry with it an array of low-level micronutrients, including iron, magnesium, copper, and boron.  It is not enough to really make a substantial difference in a maturing crop, however, so it is probably a good idea to supplement coco coir with a nice liquid organic fertilizer packed with micronutrients, like liquid kelp, which is immediately bioavailable to the roots of our short-term wheatgrass crop and can easily be added to the coir’s initial water bath.  Remember that wheatgrass does not require a whole lot though, so pour judiciously.  Remember, you just need enough to carry you through those last couple of days before harvest.  Liquid kelp, while lacking in macronutrients, provides an ample supply of micronutrients, trace minerals, amino acids, and natural plant hormones to help stimulate growth and produce a nutritious baby green.  Even folks who prefer to grow in soil find liquid kelp to be a wonderful soil amendment.  

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In summary, coco coir offers growers a sustainable growing medium that is pretty stable from package to package in terms of pH and nutrient analysis, making crop planning more controllable and predictable. Soil, on the other hand, can vary greatly depending on its source and needs to be tested with a soil tester and amended accordingly. Whether growing in soil or coco coir, water pH is a major factor. A device for measuring water pH is a must for any grower. If growing regularly within confined indoor growing areas year-round, coco coir offers many benefits in terms of cleanliness and storage. If growing in a greenhouse or outdoors, soil offers a more complex and often-preferred nutrient base as well as that certain intangible "earth connection." It also offers cost efficiency. Coco coir, unfortunately, requires a fair bit of price shopping and is still slightly more expensive than bagged soil (tray for tray).  The price of coco coir has come down considerably in recent years, however, and will probably equal that of bagged soil as demand continues to increase. It also offers the look and feel of soil for those who are just more comfortable growing in soil.

As a consumer, you should be aware that hydroponically-grown fruits and vegetables have been shown to nutritionally out-perform their soil-grown counterparts in European studies.   In America, the USDA has determined there to be no nutritional difference between the two growing methods.  

As to how you should grow and what you should consume, it’s all a matter of what is practical for the grower and what is preferred by the consumer. The better method, it appears, depends on the situation.

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