Legumes are an amazing family of plants. The ability to take up atmospheric nitrogen and fix that element into root nodules with the symbiotic help of bacteria — straight up miraculous. A single cow would need a few acres — incredibly dependent on the fertility of the soil. The magical thing with a cow is that after a while, the cow (or small herd, more proactively) will began to build up that soil fertility. Hummus levels need to be increased in order for the soil economy to have capital to spend. Cow pies began that process. Management practices decides whether or not that herd of cows on a few acres will be regenerative or degenerative.
Alfalfa is a well-known crop, originally cultivated in Iran, now widely known and grown across the planet. Deeply rooted, it brings water up from lower in the soil horizons then many other legumes. A mixture of alfalfa and oats as a parent crop is commonly used to began a field of alfalfa for baling. I think alfalfa is a beautiful and useful legume. Do I want to eat it? No, although I believe they use the sprouts in Indian dishes.
No, Instead of the fossil fueled processing of other shallow rooted legumes, I would rather plant a field of alfalfa for livestock to harvest and process themselves into incredibly delicious and nutritious food. That is one discing and planting. Then, year after year, that nitrogen fixing plant and grazing animals fertilize the soil and build the humus level, increasing the cation exchange rate and water retention levels.
So, there are many factors within this topic that warrant concern, and I believe the regenerative capacity of the landscape itself is the most important, for the future of the planet overall.