The Benefits of Organic vs Chemical Soil Treatment

Posted on Tuesday, February 14, 2023 · Leave a Comment 

On a cold and snowy day I paused to think back a few years to a conference I attended run by the Ecological Farming Association in Pacific Grove, California. There were several sessions by scientists presenting research confirming what organic gardeners have always known: organic techniques yield plants that resist disease and insects better, and produce better quality and healthier vegetables. There was even data presented indicating that organic practices can reduce weed pressure! I dug out my notes, and would like to share some of what I learned.

 

Dr Larry Phelan, a research scientist at Ohio State University, explained that he wanted to see if organically grown plants attracted insect pests differently than those grown using conventional techniques. He collected soil from two farms that were across the road from each other. The soils were identical except for how they had been tended for the past several years. One farm was organic, the other conventional.

 

Organic corn from my garden never gets treated with chemicals

To reduce other variables, Dr Phelan brought the soil to his greenhouse, and potted it up in large containers. He then grew corn in containers, adding chemical fertilizers in some, fresh cow manure in some, and composted manure in others, using both types of soil for each method. When the corn was at the appropriate size, he released corn borers into the greenhouse, and watched what happened.

 

Not surprisingly, the corn borers preferred the corn grown conventionally. Not only that, the long term history of the soil mattered. The soil from the organic farm had higher levels of organic material in it, and consistently was less attractive to the borers – even if used with chemical fertilizers.

 

Why should this occur? Dr Phelan explained that plants evolved over the millennia getting their nutrients through the soil food web, depending on the symbiotic relationships between plants and microorganisms. Chemical fertilizers are imprecise, providing nitrogen for fast growth, but often giving too much nitrogen, or providing it all at once. Soils rich in organic matter provide nitrogen and other needed nutrients in a slow, steady stream – the way Mother Nature does it.

 

He said that when a plant gets too much nitrogen, the excess is stored in the form amino acids, the building blocks of protein. For insects, this is like candy for kids or drugs for addicts: they can detect it, and go to the source.

 

This artichoke from my garden was grown without chemicals

In another experiment, Dr. Phelan grew soy beans hydroponically, varying the amount of nutrients present. The soy bean loopers preferred plants that were out of balance nutritionally. But not just nitrogen mattered. Iron, boron and zinc levels were important, too. And of course, those elements are not present in conventional fertilizers. Chemical fertilizers only offer nitrogen, phosphorus and potassium. Good soil enriched with compost should have everything your plants need.

 

Dr. Autar Mattoo of the United States Department of Agriculture Research Station in Beltsville, Md., also presented some very interesting findings. He compared the health of tomatoes grown with chemical fertilizer on black plastic versus that grown organically using a mulch of hairy vetch, an annual cover crop. He found that tomatoes grown with hairy vetch was dramatically better at resisting fungal diseases, especially those that cause blackening and dropping of leaves, which is often the bane of gardeners.

 

Dr. Mattoo explained that the vetch fixes nitrogen when growing. Which is to say, it extracts nitrogen from the air and turns it into a form that plants can use. It was mowed down before flowering and allowed to stay on the surface of the soil, producing a considerable biomass to nourish soil microorganisms.

 

Compared to chemical fertilizer and black plastic, Dr. Mattoo found a 25-30% increase in yield using vetch. He explained that eventually the organic tomato plants would develop fungal diseases, but that for the first 84 days after transplant (late August for us), there was virtually no leaf blackening. At the same time, the tomato plants grown conventionally were severely damaged.

 

A selection of my homegrown tomatoes

He attributed much of the difference to hormone signaling. Anti-fungal proteins can be produced when specific genes are activated, protecting leaves. He explained that depending on the environmental conditions specific genes are turned on or off. He was able to show this by photographing specific genes in the leaves of the tomatoes to see their size and thus their levels of activity. It appears that something in the vetch stimulated the tomatoes to produce those anti-fungal proteins.    

 

What does all this prove?  Being an organic gardener has many benefits, and scientists are just catching up with us! So as you plan your garden projects for the spring, think about giving up your use of chemical fertilizers. There are plenty of organic fertilizers made from natural, biologically-created ingredients like oyster shells, peanut hulls, cotton seed meal and naturally occurring minerals like rock phosphate and green sand. And of course, compost is a terrific way to increase biological activity in your soil.

 

Many thanks to all you readers who have donated to support Notes from the Garden. If you have been enjoying the column, learning from it and wish to donate, please go to my website, www.Gardening-Guy.com and go to store/donations and follow the prompts. Or do it the old fashioned way, and mail a check to Henry Homeyer, PO Box 364, Cornish Flat, NH 03746.

Filed under Article · Tagged with chemical soil amendments, growing organic vegetables, organic soil amendments

More on Growing Great Veggies

This year Mother Nature, if she were a middle school student, would be at best a tease, and at worst a bully. Or maybe the Wicked Witch of the West. She gives us warm and sunny – then threats of snow or hail. Come on, Spring, let’s get with the program. We have veggies we want to plant!

Corn seeds planted in plug tray indoors

Recently I wrote a column that promised tips on growing vegetables “A to Z: Artichoke to Zucchini” – but didn’t finish the B’s and skipped to zucchini. Huh. Today I’ll be less ambitious: The last of the B’s and most of the C’s. There really are a lot of great veggies we can grow.

Beets are best started outdoors once the soil temperature has warmed to 60 degrees or even warmer. Yes, they grow well in cool temperatures, but are slow to germinate in cold soil. Plant 2 to 3 inches apart, and be prepared to thin them in a month to 3 to 4 inches apart. Each “seed” is actually a seed capsule containing 2 to 6 seeds. They like soil that is near neutral in pH, so if you have acidic soil, add a little limestone. And they are deep rooted, so plant in fluffy soil for best results.

Hoping to jump the gun this year, I planted some beets in flats indoors on April 10. I started them on an electric seed warming mat but only got 20 percent germination, and the plants have long stems and are flopping over – even with bright fluorescent lights over them. I won’t do it again. I’ll plant mine outdoors this week.

Carrots also want fluffy light soil – and few if any stones. Comb through the soil carefully to get out rocks – I use a CobraHead weeder for that. Add lots of compost and some bagged organic fertilizer at planting time and again in early July.

Carrot seeds are tiny, but it’s worth your time to plant them individually, or nearly so. It will save a lot of time thinning them later on. Put seeds in the palm of one hand, and push one away from the rest with a pencil or pocket knife. Pick it up, plant it, and repeat. Tedious, yes. I like to plant them about an inch and a half apart, and thin to 3 inches when the thinnings are big enough to be worth eating.

Cauliflower is fussy. If it gets too hot or too cold it will “button” and not form a proper head. And unlike broccoli, cauliflower makes no side shoots (with rare exceptions). There is a purple one that I have grown, gorgeous in the garden but it turns gray when cooked.

Likewise, I don’t grow celery. It attracts slugs, gets woody and tough if the soil dries out, and is generally unsatisfactory. But I’m a serious cook and often need that celery flavor. Instead, I grow celeriac, also known as celery root. This is a great root crop that is pest free and stores for a long time. It’s funny looking with lots of roots that I cut off the bulb. Then I chop or grate it.

Celeriac

Celeriac, unfortunately, is not often sold in 6-packs at the garden centers. But it’s worth asking for it as the seeds germinate slowly and take a long time to get big. I planted mine on April 10 and they are just an inch tall 5 weeks later. Still, it will grow well into the fall so you could try planting seeds. Celeriac needs soil with plenty of moisture all summer.

I avoided growing corn for decades, instead I bought just a couple of ears at a time. I’m a bit like a raccoon: I tend to glut on it when there’s plenty in the garden ‘cause it’s so darn tasty! But for the past 2 years I have grown it. Here’s what I have discovered: you do need to plant it in blocks of 4 rows to get good pollination. And it needs plenty of supplemental nitrogen to do well. Last year I ran out of fertilizer and thought that since the soil was good, it would do fine. But corn in that section was short and spindly.

Fencing is probably the best to keep out coons, but I also used some solar powered blinking red lights that are said to scare them off (www.niteguard.com). Those are touted as deer repellents, too. I had some raccoon damage, but I probably needed more of them as the corn patch was very long. You need a minimum of 4 units to point in every direction.

Cucumbers are a summer favorite of mine, and I’ve already started some seeds indoors. They’ll go outside in mid-June after frost and when the soil is nice and warm, say 65 degrees. I used to plant seeds outdoors, but the plants were often killed by striped cucumber beetles that would strip off all leaves in a single night. Now I plant them when they have vines 6 to 12 inches long with some nice big leaves.

If you have had trouble with beetles but want to direct-seed your vine crops, you can cover the hills with row cover, also called Reemay. It is a thin agricultural fabric that breathes and lets sunshine and rain through. But sometimes the beetles, which emerge from the soil, are already waiting for you before you put it down. Be sure to rotate your planting sites for vine crops like cukes.

Mother Nature, if you’re listening: I’ve had it with this weather. Don’t make me release the flying monkeys.

Henry is now blogging twice a week. See the blog at https://dailyuv.com/henryhomeyer. You can sign up to get an e-mail alert every time Henry posts something.

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