A recent review article in the publication “Trends in Plant Science” caught my attention and to be honest I have read it several times. The title is, “Building soil sustainability from root-soil interface traits,” and is written by several authors all from wonderful universities or institutes throughout the world. The title tends to overwhelm you until you read the first couple of sentences, “By reversing our thinking of how root-soil interface traits affect the function of the rhizosphere (the area around a root where microbes survive) there is considerable opportunity to restore degraded soils, mitigate greenhouse gases, and enhance biodiversity. Breeding crop varieties with the target of improving soil health and reducing soil degradation will produce better condition for crop growth through more efficient resource use and stress tolerance.”
The authors propose that plants are known to have a huge impact on soil properties, but these plant properties are generally ignored in plant breeding in favor of yield. They say, “with the shift towards reduced tillage and smaller input of both fertilizer and chemicals that a plant’s capacity to alter soil structure and the rhizosphere microbiome will become increasingly important.”
In this article they estimate that under the soil under a small grain crop is 2% roots but 50% rhizosphere and this could be even more with better breeding. The properties of the rhizosphere influence both plant growth and the soil environment and form the place where the plant gets nutrients from the soil. Also, a huge amount of microorganisms’ cycle nutrients and compete against plant pathogens in this rhizosphere.
Breeders’ may now have new tools because Quantitative Trait Loci (QTLs) related to this entire concept of improved rhizosphere and rhizosheath (area around the root and the soil that adheres to the root) have been found, and because they are known, breeders can select for plant varieties with these traits. For example, they have found that different varieties of barley can vary by over 500% in rhizosheath size. A larger rhizosheath means great resistance to stress including drought with a direct benefit to the improvement of soils around the root rhizosheath.
I really appreciate this last paragraph! “A genotype’s capacity to engineer favorable soil properties at the root surface could enhance its fitness under variable field conditions. We have shown evidence that selecting genotypes for favorable root–soil interface traits can also improve yield with minimal metabolic cost. The impact of plant roots on soils has been appreciated for centuries, but it is only now that new emerging technologies are unravelling the mechanistic processes of how plant root traits form the rhizosphere and impact both plants and soils. We are only at the beginning of understanding whether rhizodeposition and root hairs could be selected for more sustainable soils, but the emerging evidence is positive and compelling.”
If this is interesting to you the full article can be accessed here: https://agrilifeorganics.files.wordpress.com/2022/06/great-building-soil-sustainability-from-root-soil-interface-traits.pdf