Healthy Soil Converts Nutrients Efficiently

When the soil biota are healthy, a veritable jungle thrives underfoot. Some critters are easy to spot: the beetles, worms, ants, and maggots. Yet, a host of others indiscernible to the eye live in the soil. All these – the viruses, bacteria, algae, and fungi – are hard at work helping to feed the bigger soil critters and, most importantly, the plants.

"Biologically active soils provide the nutrients needed by the plants, including nitrogen," says Kristine Nichols, formerly a USDA-Agricultural Research Service soil scientist, now serving as the chief scientist for the Rodale Institute in Kutztown, Pennsylvania.

"Such soils also have the internal mechanisms needed to resist pests, so farmers can reduce pesticide applications," she adds. "This benefit, combined with the reduced need for fertilizers while maintaining or even increasing yields, offers huge economic gain for the producer."

The Brown Revolution
Farming and ranching with the purpose of feeding and building life in the soil is what Nichols calls the Brown Revolution. "It's all about recognizing soil as an essential, living resource and focusing on feeding the soil biota first and letting crops and forages grow from this life in the soil."

Active soil biota process into a plant-available form all the nutrients residing naturally in soil, in root exudates, and in residue. This work decreases the need to supplement with commercial fertilizers.

In the absence of active soil life, nutrients must be supplied primarily through fertilizers, with often-escalating inefficiencies.

"Nitrogen-use inefficiencies have been increasing since the 1960s, even though our yields have increased," says Nichols. "The amount of N needed to produce a bushel of grain is increasing, but we're losing more N from the system than is actually being used by the grain."

The inefficiencies resulting from inactive soil biota originate, in part, from man-made plant laziness. Because of precision application of fertilizers, plants don't need to work with soil biota to track down nutrients in the soil.

"By finding ways to encourage plants to work with the soil biota, soil nutrients can be put into a plant-available form during the growing season," says Nichols. "One way to do this is to keep living plants growing in the soil as much as possible in order to feed the soil biota through the roots. The growing of cover crops, for instance, can extend the time that living plants are growing."

Maintaining surface residue by reducing tillage also helps. "The biota will process some of that residue into plant-available nutrients," says Nichols.

Reducing tillage also preserves soil aggregates, which are the microbial habitats of the fungi and bacteria that are essential to the plants' assimilation of nutrients.

Adding livestock to a cropping system further increases biological activity in soil. "The livestock bring in other micro-organisms," says Nichols. "They also help plants give off exudates, and their hoof action incorporates residue into the surface of the soil.

"There are a lot of different approaches to renewing soil biology, which serves an end goal of improving productivity and sustainability," she says.