Thursday, November 12, 2009

Simple Soil Chemistry and Organic Amendments for your Wheatgrass Crop

by Ellen McGlynn

So you've selected a soil that looks pretty good and now you want to get soaking those wheat berries and growing that wheatgrass. Right? Stop! Chances are, your wheat berries will sprout and grow acceptably well in the soil you've chosen if you've followed the guidelines in my previous post, but it's always a good idea to test your soil first for basic nutrients in order to optimize your wheatgrass' growing and nutritional potential. (Organic soil amendments pictured far left to right: volcanic ash, bone meal, dried blood, lime).

As I’ve mentioned before, when purchasing your soil, make the effort to buy all of your bagged soil from the same pallet. This logic extends now to the second phase of the testing process, where you will want to test for macronutrients only once with a genuine soil testing kit and be pretty sure that the same test results can be applied to all of the soil in your new stock.

Now, with so many basic soil testing kits on the market, which one should you choose? If you recall back in one of my earlier posts, I waxed on about a certain EPA issue in my back yard. Well, I used my time well with those folks and had a nice chat about what they considered to be a good quality soil testing kit for my growing ambitions. Their recommendation was La Motte. La Motte kits are more expensive than the Rapitests you’re likely to find at your local garden center, but an impressive little soil testing kit from La Motte can still be had for under $70 online. I bought mine from the Biocontrol Network website. Complete with two highly informational soil manuals and a companion CD, this little recipe box full of test tubes and solutions to measure your soil’s pH and macronutrients is a must for any serious gardener's greenhouse.

Starting with the pH, a measurement of your soil’s acidity or alkalinity, you will want to make sure that your wheatgrass soil measures on the slightly acid side. Every plant has its optimal growing pH, and wheat’s optimal pH is between 6.0 and 7.0. I once had a client who followed a strictly alkaline diet and was very reactive to even slightly-acidic foods. She was not too pleased to learn that I grew my wheatgrass in a slightly acid soil despite my justifications for doing so. I lost the customer, but my position on soil acidity still stands strong. Wheatgrass grows best in a slightly acid soil measuring around 6.5. I know this from growing thousands of wheatgrass trays. Without a proper soil pH, even the most nutritious soil will not live up to its full potential. This slight acidity is necessary for the grass to assimilate not only the macronutrients in the soil--the potassium, phosphorous, and nitrogen--but also the micronutrients such as iron and zinc. If your soil is too alkaline at 7.0 or greater, you will want to add peat moss to lower the pH. If your soil is too acid, measuring below 6.0, you will want to add pulverized lime to help “sweeten” it. Lime is typically a slow-acting soil amendment, so the more highly pulverized, the more fast-acting it will be, which is what you want since tray-grown wheatgrass only has about nine days of soil contact. One level teaspoon per 10” x 20” tray should be sufficient.

Next on the importance scale is Nitrogen. Nitrogen is responsible for wheatgrass’ notoriously green color. My favorite choice for greening has always been to mix my deficient soil with one part bagged composted manure—NOT fresh manure. Adding fresh manure will “burn” your grass, and it's just not an acceptable practice to add fresh manure to low-lying edible crops in the same growing season. For nitrogen-deficient soil, you may alternately want to consider adding a level teaspoon of dried blood per tray or, if the thought of adding dried beef and pork blood to your wheatgrass turns your stomach (as it does mine), a teaspoon of alfalfa meal. Suffice it to say, simply substituting composted manure for one-fourth of my regular soil mix has always provided an ample nitrogen fix.

Next we move on to Phosphorous. Phosphorous promotes strong root growth in your wheatgrass and helps it grow quickly and with vigor, ultimately resulting in good crop yield in a reliable time. Two words: bone meal. If your soil is deficient in phosphorous, add just a teaspoon per tray to help make the correction.

Potassium. This macronutrient actually has a lot to do with how your wheatgrass tastes. A nice sweet wheatgrass is probably rich in potassium. While potassium is not the only contributing factor toward a wheatgrass crop’s sweetness, it is a major player, so keep your soil levels in check. It’s hard enough to drink wheatgrass juice, let alone bitter wheatgrass juice. Potassium is also responsible for maintaining water pressure within a plant, making for a more plump, strong grass. This is especially important as your crop nears its harvest. Trust me, when you are responsible for harvesting dozens of trays in a single day, you notice how convenient it is to have a crop that isn’t keeling over.

Now, while that is basically it for the major players, I must confess to also giving my wheatgrass a boost in the micronutrient department by adding a teaspoon of volcanic ash per tray. I’ve been lucky enough to find a fairly local bulk supplier, and I happily make that 60-mile pilgrimage to Vestal, New York, every year to stock up on what, to me, has become my own wheatgrass recipe's not-so-secret secret ingredient. I cannot state exactly what volcanic ash does for my grass since I do not have the sort of soil testing capabilities I need to manage that process, though I can say that volcanic ash is known to impart a whole host of micronutrients and trace minerals to soil, and the look of my grass has improved since incorporating it into my soil recipe. While the product I use is not available for retail sale, you may wish to use a volcanic ash product called Azomite to add trace minerals to your soil.

Keep in mind that the organic amendments I’ve mentioned in this article, aside from the volcanic ash, are perhaps the most easily-found organic amendments in your local garden center or hardware store, but there are also many more options out there that can be easily found online at any number of organic gardening websites-- items such as bat guano and fish/sea fertilizers. There are many ways to attack your fertilizing situation organically, and I haven’t even touched on composting yet, so if you have the time to experiment, I highly recommend it. Some organic fertilizers are fast-acting while others may take a whole outdoor growing season (or even years!) to realize maximum soil benefits. Sometimes the amendments I choose only impart modest benefits to my immediate wheatgrass crop but provide tremendous long-term benefits to my overall outdoor compost. You be the judge as to what you are comfortable using and what your ultimate goals are. I have often considered “making soil” to be like making a cake; therefore, I tend only to use ingredients I am mentally comfortable with. I’m not comfortable with the idea of using bat guano. Yet.


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  2. I have read the post and the information which you have shared that is really good and useful.

  3. Hello,
    I have just read your post and am a grower of wheatgrass in Edinburgh (Scottishwheatgrass dot co dot uk) and just discovered that PH tests of the same batch of soil turn out slightly more acidic after 24 hours. I tested my soil yesterday and then re-tested the same batch this morning (after letting it sit overnight) and it turned a shade lighter. That makes me think that the acidity probably increases as the trays go through the growing cycle, also considering that I use tap water for watering them. I cannot complain as the wheatgrass turns out ever so potent, but I guess that the soil has a tendency to turn the acid way rather than the alcaline way. Do you think that's right?