Posted 11/12/2012 14:33 (#2693122) Subject: Some thoughts on fungi and nutrients
I kind of had an AH HA moment recently. I add this to contribute based on the recent discussions on adding Fungi of some name brand as a root growth promotor or for whatever reasons they are sold, and apparently have quite a following lately. As you learn, it is important to understand that there is more to science than just buying cleverly marketed inputs.
Well in January, one of the funniest things at National No-till Conference, was Gabe Brown (look up on youtubeif you want) picking on Dave Brandt (also check youtube) that he needed to "take out the pacifier" if he wanted to get his soil biological system working correctly. The scenario is that Brandt uses 60 lbs of Nitrogen to grow his corn crops that are otherwise grown with legumes/cover crops/organic fertilizer etc, and that he obviously sees a positive net return to this (60 lbs) input. Gabe is saying, that he has learned, the addition of this fertilizer, is really holding back the biological soil/plant/microbial system from its potential. Or that the "cost" is greater than the nitrogen alone. So, lots of people don't "see" or believe what Gabe is saying, that is fine. It is what he has been taught/believes/is selling/whatever.
More recently, I am currently in a Soil Microbiology class (PhD). We had a guest lecturer, who specializes in mychorrizal fungi (those that operate as root extensions, they use the plant for Carbon, and contribute other nutrients to the plant). I took some bullet notes and will share those, they are something that is definitely worth thinking about. Much of this is economically irrelevant in times of high grain prices, or low fertilizer prices, as profit trumps science every time. But if you are interested in the soil as a biological system, some good points.
-Phosphate critical for living cells. ATP
-Mychorrizal associations contribute 20-80% of P needs.
-Plants w/o mychorrizal association explore 1-2 cm3 of soil around roots.
-Plants w/ myc ass. explore 12-15 cm3 of soil around roots.
-When P or N is limiting, plants support mychorrizal assocation.
-High concentration of P or N in plants create more demand for Carbon. Then plants reduce C contribution to mychorriza or eliminate association.
-Plants spend less energy in the mycorrizal association than producing root mass for nutrient uptake.
-Hyphae (structure) reach up to 10 cm from roots.
-Phosphorus is largest nutrient uptake by myc fungi to host.
-Other nutrients taken up N, K, Mg, Ca, Mn, Zn, Cu
-Increase plant tolerance to water stress. Hyphae extract water from small pores.
-Supress root disease, improve plant health, mechanical resistance.
-Produce Glomalin to bind soil particles.
-Excess fertilizer leads to less myc association. 45 lb/A/Yr reduced colonization by 50%
-Negative correlation to high P
-Plants depend on myc to different level. Flax 90%, Corn 80%, Sorghum 60%, Wheat 30%.
-Brassica are non-host of myc fungi.
The speakers belief or prediction also included that political tensions will build over phosphate rock. The world would move from an oil economy to a phosphate economy. That is worth a whole discussion itself, as I have seen several scientists present that same view with hard data.