Grass farms its own microbes
OPINION
The Grass is Greener on the Udder Side
Reprinted From : http :// bit . ly / 2Os2KZU
I
once came across two studies that stopped me abruptly in my cognitive tracks . Both studies showed that plants were not just passive recipients of the multitudinous goods and benefits that soil microbes provide to promote their growth ( most importantly , nitrogen ) and general health .
Figure 1 : Poa pratensis
Rather , plants are active cultivators of the microbial communities in and around their roots ( their rhizosphere ), tending them carefully to ensure they thrive and provide the plant just what it needs .
The first study was on , Poa pratensis , a grazing-tolerant grass common in the Yellowstone National Park where bison and elk graze the grassland heavily in places , at times .
The
study by Hamilton and Frank done in 2001 measured the effect on soil microbes and plant growth of exudates produced by roots of Poa pratensis plants that were clipped ( to simulate defoliation ) compared to unclipped control plants .
In short : when grasses plants were clipped , they released extra , hardearned , carbon-rich exudates from their roots , which greatly stimulated the microbial community in their rhizosphere to break down organic nitrogen to a form that could be taken up by the plant .
As a result , the clipped ( grazed ) plants grew back faster and had higher nitrogen ( better forage quality ) in their leaves than uncut plants - a virtuous positive feedback cycle which probably enables Poa pratensis to tolerate chronic heavy grazing .
The second study ( by
Zhalnina et al . 2018 ) carefully tracked changes in the kinds of chemicals exuded by roots of Avena barbata ( slender oat ) into the soil over its annual growth cycle , in California .
Figure 2 : Bison grazing at Yellowstone National Park
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