The nitrogen bar

Because humans need it to breathe, I assumed for much of my life that the principal gas in the “air” was oxygen. School science classes didn’t clear up this misconception; only after I’d studied plant science on my own did I learn that oxygen accounts for about 20 percent of the earth’s air, and close to 80 percent is nitrogen. Talk about putting things in perspective! This single piece of information altered my whole human-centered view of the world, because nitrogen is a plant thing. Our precious oxygen is a mere byproduct of plant respiration (something we would do well to remember as, parking lot by parking lot, interstate by interstate and development by development, we defoliate the planet).

Plants evolved in a nitrogenous atmosphere. In illustrations depicting the imagined beginnings of life on earth, great bolts of lightning flash. Those electrical explosions, which must have been frequent and powerful, infused the surface of our planet and its atmosphere with nitrogen. After a big lightning storm, all the greens in the landscape deepen, and plant growth is almost perceptible to the naked eye — sure signs of a nitrogen rush.

Vegetables need nitrogen for lush, strong growth — but a constant supply of it, not just a lightning jolt now and again. In my small potager garden, I use several organic strategies to create nitrogen-rich soil that delivers this steady stream of grow power to my vegetables.

One of these is worm manure — lots of it. I want to be sure my manure source is organic — almost impossible unless you control the diet of the animals producing the manure, which means raising them. But most animal husbandry is too expensive, time- and space-consuming, labor-intensive and travel-restrictive to be an option for me. At my small garden parties, worms work. They are awesome decomposers and nitrogen producers.

My gardener-granddaughter, Ivy Rose, is a walking encyclopedia of worm trivia. According to her research, worms have been in the nitrogen-manufacturing business for 120 million years. Soil nourished by worm castings contains up to five times as much nitrogen as wormless soil. One worm can produce eight pounds of castings a year. 2,000 worms can enrich the soil they live in to the tune of seven pounds of castings a month.

The population of microorganisms increases 50 percent in worm-turned soil: the worms’ burrowing puts more air in it, creating an environment in which microorganisms thrive. These tiny creatures play a key role in the nutrient cycle (the transformation of dead stuff into fertilizer). When they die, micros release nitrogen in a form plants can use. And when a blend of dead micros and plant material passes through the gut of a worm, the result is super compost.

Best of all, worms are perfectly capable of “raising” themselves. Rather than farming them in bins, separating them from their castings, and hauling the worm manure around the garden, I put my energy into enticing worms to take up permanent residence right in the garden beds. Mulching, for example, is a key way to create a worm-friendly habitat.

The slowly decaying mulch, which almost always covers any area of my beds not shaded by a “living mulch” of closely spaced plants, gives the little wrigglers a steady food supply; maintains the cool, damp soil temperatures they need; and protects them from the sun’s ultraviolet radiation. (According to Ivy Rose, even mild sunlight will paralyze an exposed worm in an hour and kill it in two.) Chlorinated water also kills worms. Fortunately for my worm population, my water source is a pure Southern Appalachian spring. Mulch also reduces the need for any kind of water by at least 50 percent.

During the planting season, I mulch with old hay, bought in square bales from neighboring farmers. In winter, my raised beds rest under blankets of partly composted leaves hauled in from a nearby leaf dump. Dead leaves are a preferred food of wild worms, which is one of the reasons all those millions of leaves that fall in autumn disappear by the following summer. Worm castings are full of digested leaf particles. My granddaughter, who enjoys snooping around the garden at night with her flashlight, claims she once spotlighted a night crawler in the act of pulling a dead leaf into its burrow.

Many worm farmers feed their “stock” cornmeal as a protein supplement. Whenever I mulch a bed or part of one, I first sprinkle a little organic cornmeal on the surface of the soil. Cornmeal attracts worms in droves. Sometimes I sheet-compost first with a layer of kitchen waste, then sprinkle on the cornmeal. I keep citrus and onion waste in a separate pile outside the garden, because worms don’t fancy either one.

Plants are also part of my nitrogen-renewal program. My sources of “green manure” are few and simple. Whenever a crop of beans or peas is finished, I cut it off at soil level, leaving the roots of these legumes, which have been a habitat for bacteria that take nitrogen from the air and fix it in the soil. (“Micro-magic,” Ivy Rose calls this awesome trick.) When a legume dies, so do its colonies of bacteria, releasing nitrogen to other plants. I follow a nitrogen-guzzling crop like broccoli with peas or beans. Alfalfa is the queen of legumes, but I prefer not to grow cover crops in the garden beds. Turning them under is too much work, and it disturbs both the soil and the resident worms. My solution is organic alfalfa meal from my local nursery, sprinkled liberally on all the beds when I close down the garden in the fall.

Comfrey is one “green manure” plant I do grow around the edges of the garden, both for its appearance and for its nitrogen-rich foliage. I harvest only the big leaves, not the whole plant (which is a perennial), laying the freshly cut foliage right on the garden beds or compost pile. Comfrey is so fast-growing and prolific, I can harvest it twice a season, in midsummer and again in fall.

At the end of the fall gardening season, I prepare all the beds the same way. First I blanket each one with composted hardwood leaves and sprinkle it with cornmeal. A layer of fresh, green comfrey leaves comes next, then a generous application of organic alfalfa meal, which not only boosts soil nitrogen but accelerates the decomposition of the other materials. Finally, each bed is topped off with hay to keep everything else from blowing away. Whenever I have a bucket of kitchen scraps during the winter, I pull back the hay mulch on a bed, spread on the food waste, sprinkle it with a little cornmeal and cover it up.

I rarely get my soil tested. The size, intense green color and strong growth of my crops all assure me that the nitrogen supply in my soil is adequate. The recipe is simple: year-round mulch and a synergy of legumes, comfrey, microorganisms and free-range worms … plus a lightning bolt every now and then.