Mid-spring 1977, in my role as agronomy cooperative extension agent for Otsego County, I attended a field crop demonstration at one of Cornell’s off-campus research facilities. Several agronomy professors were stationed at their own demonstration sites. These educators would explain the details of their experiments to guests, mostly farmers. The presentation that I remember best was given by Robert Seaney, PhD.
Seaney explained how alfalfa that’s part of mixed hay stand is much more likely to survive cold weather freezing-thawing-based heaving than a pure alfalfa hay stand. The reason for this, he explained, was that the fibrous root networks of the timothy, orchard grass, fescues, etc. function as a shock absorber. The alfalfa’s nitrate-forming root nodules are much less stressed… and stretched… imbedded in the root system of companion forage grasses…. compared to clear-seeded alfalfa’s root system absent such padding. Seaney showed heaved-out alfalfa plants… in the clear-seeded plot… that were flopped on their sides, dead or at least comatose.
I don’t recall whether Dr. Seaney used the term “symbiosis” in his talk, but that phenomenon is what was taking place with these forage species. My Eco-Farm, An Acres U.S.A. Primer (Charles Walters, C.Z. Fenzau, 1996) defines symbiosis thusly: “Life together of two dissimilar organisms with resultant mutual benefit, each depending on the other.” With the alfalfa and its grassy companions, here’s what was taking place: the legume was pulling the nitrogen (N) out of the atmosphere (atmosphere including air vacuoles between soil particles). The N is crafted into nitrates by the nitrogen fixing bacteria (NFB) colonies (nodules located on the legume’s roots). The legumes make the nitrates into their own tissue protein (sort of an oversimplification), with enough nitrates left over to share with their grassy companions (so they can make their own proteins). In return, the grasses form fibrous mat-like roots that help absorb the shock caused by frost-based freezing and thawing. Grasses lack classic NFB colonies, although there are some other bacteria that exhibit limited nitrogen fixing skills.
We can expand “symbiosis” into the concept of “biodiversity”. That’s simply defined by Oxford’s on-line dictionary as “the shortened form of two words ‘biological’ and ‘diversity’. It refers to “all the variety of life that can be found on Earth (plants, animals, fungi, and micro-organisms)… as well as to the communities that they form and the habitats in which they live.” A simple, fairly well-known, example of biodiversity is referred to as the “three sisters”, a cropping practice long-established by Native Americans. Southern indigenous peoples planted climbing (pole) beans, winter squash, and maize. Northern indigenous peoples grew similar beans, maize, and pumpkins. The leguminous beans do the nitrogen-fixing thing, having enough nitrate formed for themselves as well as their maize and cucurbit neighbors. The pole beans climb up the maize (which was first cultivated in Central America). “Sister Squash” shades the ground with its large leaves to provide a good growing environment for itself and the other two “siblings”… including helping retain moisture.
Another cropping team that I’ve had good luck with… this time just a pair… is millet and buckwheat. This last crop can tolerate lower pHs (mid- to low 5s), too little water (and sometimes too much). Millet was (still is) an “easy keeper”. Millet needs the least amount of precipitation to form a pound of forage dry matter, compared to all other forage crops and is also tolerant of mid- to low-5 pHs. My initial fear regarding planting buckwheat with any other crop was spawned by that broadleaf’s allelopathy (natural herbicide) trait. Even though buckwheat strongly discourages nutsedge, it appears to be at peace with millet. Buckwheat also boasts acidulation. This means that its root tips secrete their own organic acids to liberate soil-complexed minerals, particularly phosphorus. As non-legumes, neither millet nor buckwheat boast nitrogen-fixing capabilities, but often, planted on a plowed-up sod, enough N is kicked loose… by the decomposing grasses and legumes… to satisfy these two crops.
Another unexpected peace treaty exists between buckwheat and tillage radish. The tillage radish has been bred to produce a large tap root, which penetrates compacted soil layers, so as to increase soil aeration and water infiltration. This, in turn, decreases compaction and increases rooting depth opportunities for successive crops. Any potential allelopathic issues appear to be successfully deflected by this deep-rooting distant cousin of cabbage and kohlrabi. A good seeding rate (drilled) is 25 pounds per acre of buckwheat, and five pounds per acre of daikon. Plant the last half of August, the earlier the better in that time window. Planting after Labor Day may short this duet on growing-degree-days.
My most recent addition to the novel forage seed blend portfolio centers on another pair: namely forage oats and winter rye grain. Following any crop, plant 50 pounds each of oats and winter rye per acre, drilled. If broadcasting seed, increase rate by 25%. Aim for the third week of August. Rye boasts moderate allelopathy, but such does not appear to threaten oats at all. These two small grains come on very nicely, and offer the possibility of a forage harvest in mid- to late October. But do not leave a stubble shorter than four inches, since such will drag out the recovery period, impairing rye’s ability to build up root reserves to make it through winter. Oats will die when temperatures dip down into the teens. Rye will just rebound after that first real cold snap that killed the oats. Spread manure on the rye throughout the fall; if it hasn’t gone totally dormant, rye will metabolize 50-75 pounds N per acre. This will spur on rye’s reawakening, hopefully in mid-March next year. This past spring, winter ryes, wheats and triricale—despite a slow cold spring—kicked into high gear a little later than normal, but much, much faster than perennials.