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Five innovations that boost soil fertility

Farmers and scientists are going beyond the massive use of chemical fertilizers to find innovative methods to improve soils and yields.

By Joseph ZaleskiNourishing the Planet / November 30, 2011

A farmer threshes maize (corn) in Abay, north of Addis Ababa, Ethiopia. Techniques from applying "green manure" to "microdoses" of fertilizer are being tried to improve degraded soils around the world and boost agricultural output.

Barry Malone/Reuters/File


Crops need air, sun, water, and soil to thrive. When it comes to soil, however, quality usually trumps quantity. Rich and fertile land boasts a healthy mixture of phosphorous, potassium, and nitrogen, along with water, air, and soil micro-organisms that break down organic matter.

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But what happens when these elemental building blocks are disrupted? The Green Revolution of the mid-20th century implemented a variety of practices, including the widespread use of pesticides and fertilizers. Yet, improperly applying the Green Revolution’s principles can sometimes do more harm than good.

Overfertilizing and destructive land use practices, including deforestation, can deplete vital nutrients in soil, and no amount of inorganic fertilizer can replace fundamental topsoil. In addition, higher annual temperatures, more extreme weather events and persistent droughts, and increasing population are also exhausting the land. These conditions are creating a cycle of soil degeneration which is stunting agricultural yields and presenting farmers with a new crop of concerns.

Today, Nourishing the Planet provides five methods that farmers and scientists are using to combat rising soil infertility.

1. Cover Cropping / Green Manure: In our State of the World 2011 report, agroecologist and author Roland Bunch defines cover crops / green manure as “any plant, whether a tree, bush, or vine, that is used by a farmer to … improve soil fertility or control weeds.” In practice, cover crops are planted alongside or interspersed with other crops to cut soil-eroding wind, prevent overexposure to the sun, and stimulate a healthy soil system. Just as farmers will turn to manure to bolster the soil, they can also clip and spread cover crops’ leaves as organic green manure.

Cover Cropping / Green Manure in Action: According to Roland Bunch, there are more than a million farmers now actively using cover crops / green manure worldwide. In Africa alone, there are over 120 plant species that are being used or could be used for this purpose. One promising example is the cowpea (also known as the black-eyed pea). This legume is both a nitrogen-fixer, which means that it takes nitrogen from the air and replenishes it in the soil, and deeply rooted, which makes it resistant to drought. Furthermore, the cowpea itself is a nutritious staple food for both people and animals.

2. Microdosing Fertilizer: According to the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), microdosing is defined as “the application of small, affordable quantities of fertilizer with the seed at planting time or as top dressing 3 to 4 weeks after emergence.” This precise process stands in stark contrast with the field-wide fertilization used by many farmers. Fertilizers are often very expensive for farmers in the developing world, particularly in sub-Saharan Africa. Microdosing can help reduce fertilizer costs, while also targeting the seeds farmers want to cultivate.

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