Usually this implies genetic improvement through selective breeding, hybridization or gene tweaking but another sometimes overlooked enhancement is inoculation with beneficial microorganisms by the seed vendor, assuring that each seed will have an opportunity to quickly associate with these microorganisms and get full benefit, including some protection from harmful microorganisms that can otherwise associate with plant roots.

Perhaps the most common inoculant is rhizobia, a nitrogen fixing bacteria that nodulates on the roots of legumes and lives in symbiosis, bartering nitrates for carbohydrates. Legume growth is reduced by the amount of carbohydrates paid to the bacteria, but increased by the extra nitrate when that is the limiting nutrient, which is often the case. The net effect is most often positive for the legumes. There are many strains of rhizobia and it is important to use the proper strain for each legume to get full benefit.

Other inoculants are on offer, such as the bewildering variety of mycorrhizal fungi (endo, ecto, yada yada), but one that is increasingly interesting to grass farmers (which includes most of the grains that feed the world as well as graziers) is Azospirillum brasilense, a free living nitrogen fixing rhizobacteria long valued for its beneficial effects on root growth. Inoculated plant roots lead to an enhancement of water and mineral uptake due to increased density and length of root hairs, and so increased root surface area. The effect arises form secretion of plant growth promoting substances such as auxins, gibberellins, and cytokinins by the bacteria. The nitrogen provided by the bacteria is considered to have a lesser effect than the root growth enhancement, but it can be very helpful in initial stand establishment.

Some studies have found Azospirillum brasilense inside roots, apparently infecting them, similar in some ways to the way rhizobia infect legume root nodules. Azospirillum has also been found infecting fungi and even human wounds. This ability to associate with a variety of hosts makes me wonder if this might not be an excellent candidate as an inoculant for biochar. The thinking is that since char provides good habitat for bacteria and fungi that benefit plants it would be a good way to introduce beneficial microorganisms to deficient soils. Mycorrhizae have been suggested as a good inoculant due to the beneficial effects in phosphorous transport, making otherwise immobile nutrients more plant available. Azospirillum would further enhance the effect by promoting root growth and providing some nitrate. And if the Azospirillum can associate with mycorrhizal fungi too the effects might compound.

The use of such inoculants might be a very cheap way to improve yields that is available to any grower no matter where they get their seeds. Even seed savers could dose their seed before planting.