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Plant Roots: Are Some Slow on the Uptake?

The mycorrhizae linkage between plants and soil fungi varies greatly. Some types of plants do not use the fungi for nutrient uptake while other plants have trouble even surviving without mycorrhizae. Clearly, the evolutionary process over millions of years has led different plants down differing paths, and bio-growers should be aware of their plants’ needs.

Based on our company’s experiments, grower feedback and published research, some of the most dependent plants are (in no particular order): Grapes, roses, melons, potatoes, beans, squash, cherries, plums, peaches, alfalfa, oaks, pines, blackberries, onions, garlic, citrus, chrysanthemums, lilies, asparagus, bananas, strawberries, turf grass, eggplant, peppers, and tomatoes.

Some plants that seem to be in the “only somewhat” category of fungi-dependence. We have observed or heard of only minor differences between inoculated and non-inoculated plants are apples, pears, rice, and somewhat surprisingly, peas.

Members of the cabbage and mustard families apparently do not use mycorrhizal fungi, although there are reports of the opportunistic fungi attaching to Brassicaceae roots when the plants go into decline - most likely to scavenge nutrients!

As with every issue involving soil biology, the sorting of plant types into fungi-dependence categories is not as simple as it might seem, particularly with plants that have been subjected to “improvement”.

Our experience with tomatoes is a good example. We were puzzled at first when we observed major differences between some varieties of test and control plants and nearly no differences between others. In time, we figured out that heirloom types and early hybrids were the most responsive, leading to the speculation that fungi-dependence has been largely bred out of newer varieties. Through careful selection, “modern” tomatoes have been developed for direct-feeding of synthetic fertilizers and can therefore be successfully grown in lifeless soils, while older varieties still retain their need for beneficial soil organisms, particularly mycorrhizal fungi.

One of the tomato varieties that we have found most responsive to inoculations is the old Beefmaster, which sets nearly every blossom when grown in good biologically active soil. It’s quite a sight to see big beefsteak tomatoes growing in crowded clusters. I also have a letter from a Master Gardener (who had been chemically-oriented) who tried a little test-versus-control experiment in his garden with two Roma tomato plants. The non-inoculated plant produced 48 full-size tomatoes - a decent yield and typical of what he had harvested in previous years. His non-fertilized inoculated plant produced 183 tomatoes. To me, this illustrated the principle that bio-dependent plants show their full genetic-potential yields only when grown in “living” soils.

For those of you who might be interested, Clear Pink Early, Pineapple, Big Girl, Lemon Boy, Burpee’s Supersteak and Park’s Whopper are others that perform much better in bio-active soils. (From a flavor perspective, I suggest any of these for your personal gardens. We look mostly at growth, yields and disease-resistance in our tests, but unscientific taste-testing does occur from time to time.) To grow fungi-dependent plants, inoculation with dormant spores at planting time and avoidance of high-analysis fertilizers are both important.

I would like to invite any of you who may have made your own observations about differences in fungi dependence to send them to me for possible inclusion in future newsletters. I think we have barely scratched the soil surface of this topic.

Cheers, and good growing, friends.

Don Chapman
President, BioOrganics, Inc.

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