In part 1 of our deep dive on legumes, we looked at how the powerful proteins of the families Fabaceae and Leguminosae can replace animal-derived products in our diet. But did you know legumes are just as powerful in the fields as they are on our plates? They are the gift that keeps on giving. While modern industrial agriculture is based on extraction — taking more from the land than it returns — legumes make both a powerful agricultural ally and a seasonally appropriate blog.

There’s a Party in My Fields, and Everyone’s Invited

Since the holiday season is upon us, let’s give this topic a more festive theme. Like many children of the 70s, my memories of holiday gatherings feature a big bowl of Chex Party Mix on the buffet table. The Mix always suffered the same fate: First, guests would pick out the tastiest ingredients, most likely a chip with all the fat and salt you could hope for. Next, they went for the less zesty but easy-to-grab pretzel sticks. Nuts were the healthier third choice. After that, only a pulverized pile of Chex bits remained in an otherwise abandoned bowl, subject to the basic equation of cold and flu season:

Total surface area of Chex remnants  X number of hands that picked through the bowl  = germapalooza

Few were brave or desperate enough to dive in for leftovers.

Modern agriculture is, in this metaphor, the saddest of holiday party mixes. While regular soil contains the stuff most crops need to grow big and strong, Chex Mix has what your average partygoer needs to snack one-handed while holding a drink. But, like those party-goers, crops are choosy. Nitrogen is the most sought-after ingredient: without it crops will be yellowish and stunted. Phosphorus and potassium are your pretzels and nuts. The practice of growing a single crop year after year is like inviting the same guests to your holiday party and serving them the same bowl of snack mix. Each year, they pick out their favorite foods and leave behind the dregs. The next year you send out the invitations and top up the bowl, just as fertilizers are added to depleted soil to get through another harvest. Each year, the party, not to mention the Chex Mix, gets a little more stale.

The Fabulous Fixation of the Fabaceae Family

What if you decided to shake it up? What if you broadened your social circle, and new attendees brought side dishes of their own? The buffet is replenished! Guests are nourished, invigorated, and happy! On a farm, “shaking it up” translates to a myriad of options. A farmer might plant a cover crop to guard against soil erosion over the wet winter months. Legumes are a fabulous choice because of their unique ability to pull nitrogen from the air and turn it into plant food, a process known as “nitrogen fixation,” reducing the need for synthetic nitrogen fertilizers. Synthetic fertilizers are extremely energy-intensive to produce, transport and apply, and their solubility causes leaching into streams and rivers, leading to algae blooms and dead zones. One of the more famous examples of this phenomenon is in the Gulf of Mexico, where the Mississippi River releases fertilizer run-off from thousands of miles of riverbank. Nitrogen that is fixed into the soil by legumes, on the other hand, doesn’t leach away. It stays in the soil for the next crop.

Mix It Up!

What if our savvy farmer steps it up another notch, rotating crops in different areas of the farm, year over year? Well, this is even better. Just like everybody has a favorite snack, each crop has different priorities when it comes to nutrients — not to mention different pests that come looking for them. Rotating crops to grow in different areas of soil year after year keeps the plants happy and the insects confused, which any farmer or home gardener will tell you is much better than the other way around.