The Plant Biology of Cover Cropping

"Rhizobium is a Bacterium" ...or so says Inge Eley, my 'plant biology coach' here where I live in Upstate New York..

We were talking about plants, and the value of cover cropping. And I had asked a question knowing l'd get a set-you-back-on-your-heels kind of answer.

My question to Inge was, "How do certain plant species set nitrogen in the soil?" I've heard about this for years of gardening, living in a farming community in Rensselaer County. She told me that the roots of plants of the Legume species, for example, develop nodules in which Rhizobium lives. This is the stuff that absorbs nitrogen from air -its most plentiful component - (78% N2, 21% 02).

So, what is there about good garden soil that we "pop-in-the-car, toss-in-the-trash" beings need to know for planetary survival? And how can Rhizobium be of any use to us in this epic struggle???

She continued to explain that Rhizobium is a beneficial bacterium. Roots of legume species left in the ground decompose leaving nitrogen for the next crop to feast upon. She further explained that nothing happens with the collected nitrogen until bacteria chemically transforms it into useable nitrogen; just what new plants need. It's like baseball: short stop scoops up the ball, but no points scored till the ball gets to second baseman, who steams it over to first baseman, each with their respective foot on the base. It's nature's high-calibre teamwork; ruthless efficiency - common in nature, rare in baseball.

So, I wonder, again looking at Inge, if the roots attract nitrogen from the air, and the roots are underground, where does the air come from? The answer says a lot about the difference between good garden soil and just plain old dirt.

It's called Diversity. Clay is hard and dense. Maybe good for roads and tennis courts, not for garden. But add ingredients like peat moss, animal manure and composted vegetation and clay becomes lighter, looser, more friendly for air and water. This time good for garden, not for roads or tennis courts.

Good soil needs to be maintained. Centuries of gardener/farmers have successfully practiced replacing soil nutrients that their crops have used up. When your plants dry up at seasons end, sow a cover crop and get out of the way. Your hard-working earthworms and bees will rejoice at the new diversity in the neighborhood, and your soil will be anxious to greet your next season's plant decisions.

"Rhizobium!" - Cute name for something so basic to survival on the planet!