Showing posts with label Three legumes. Show all posts
Showing posts with label Three legumes. Show all posts

Wednesday, February 5, 2014

Legume Trees Fix the Soil

By Liliana Usvat

Question: what can be done to reverse the loss of the soil on large area due to deforestation and desertification?

Nitrogen-Fixing Trees Help Tropical Forests Make a Comeback

Some species of trees can restore lost nutrients in deforested areas, helping other trees to grow.


Denuded forests were efficiently restored in a few years, mostly with the help of leguminous plants that fix atmospheric nitrogen and pump it into the soil.

Nitrogen-fixing trees helped secure a large amount of carbon in just 12 years. In just about a decade, the new forests had accumulated 40 percent of carbon found in old, mature tropical forests. Legume trees contributed to nearly half of the carbon "sink.

Trees turn nitrogen fixation on and off according to the need for nitrogen in the system.

Legume trees accumulated carbon nine times faster than non nitrogen-fixers during the early stages of forests' comeback. These trees even provided enough nitrogen for other trees to grow. The legume trees' secret lies in their relationship with a kind of bacteria known as rhizobia, which help the trees fix nitrogen. Tropical forest soil is often low in nitrogen.

Leguminous trees are essential for a forests' recovery and so their loss could lead to long-term problems for many species of trees, researchers said.
"Diversity really matters. Each tree species fixes nitrogen and carbon differently so species important at 12 years drop out or become less common at 30 years.

Pods of carob (Ceratonia siliqua)


Pods of carob (Ceratonia siliqua), an ancient Mediterranean crop. Great livestock fodder and edible for humans as well. Courtesy Wikimedia Commons.
These trees are providing more than just food for animals. Livestock enjoy the shade they provide, especially in the tropical sun. Many of these trees fix nitrogen. Some even have pods edible for humans.

 The pods of Acacia nilotica



The pods of Acacia nilotica, from African semi-arid savannahs. Courtesy Wikimedia Commons.

Cassia grandis

 

Cassia grandis, from the humid tropical Americas. Courtesy Wikimedia Commons. 

The North American honey locust (Gleditia triacanthos)

 

The North American honey locust (Gleditia triacanthos), a good choice for cold temperate climates. Courtesy Wikimedia Commons.

The sweet pods of honey mesquite (Prosopis glandulosa)



The sweet pods of honey mesquite (Prosopis glandulosa), a North America nitrogen-fixing tree for cold, arid landscapes. There are mesquites throughout the dry Americas as well as native species from Africa and Asia, for highlands and lowlands, arid and semi-arid climates. Courtesy Wikimedia Commons.


Locust Tree


Locust trees transformed the ecosystem by adding nutrients. The soil analysis revealed that locust trees increased soil organic matter and nutrients, nearly doubling local nitrogen levels. 

Leguminous Tree Kowhai



Flowers of the leguminous tree, Kowhai, the national flower of New Zealand

Nitrogen Fixing Trees for Permaculture


Nitrogen fixation is a pattern of nutrient cycling which has successfully been used in perennial agriculture for millennia.  importance in agriculture.

Three legumes (nitrogen fixing trees, hereafter called NFTs) are especially valuable in subtropical and tropical permaculture. They can be integrated in a permaculture system to restore nutrient cycling and fertility self-reliance.


On unvegetated sites, "pioneer" plants (plants which grow and thrive in harsh, low-fertility conditions) begin the cycling of nutrients by mining and accumulating available nutrients. As more nutrients enter the biological system and vegetative cover is established, conditions for other non-pioneering species become favourable. Pioneers like NFTs tend to benefit other forms of life by boosting fertility and moderating harsh conditions.

Nitrogen fixing trees are often deep rooted, which allows them to gain access to nutrients in subsoil layers. Their constant leaf drop nourishes soil life, which in turn can support more plant life.

The extensive root system stabilises soil, while constantly growing and atrophying, adding organic matter to the soil while creating channels for aeration.

There are many species of NFTs that can also provide numerous useful products and functions, including food, wind protection, shade, animal fodder, fuel wood, living fence, and timber, in addition to providing nitrogen to the system.

Nitrogen: From the Air to the Plants
Nitrogen is often referred to as a primary limiting nutrient in plant growth. Simply put, when nitrogen is not available plants stop growing. Although lack of nitrogen is often viewed as a problem, nature has an immense reserve of nitrogen everywhere plants grow – in the air.

Air consists of approximately 80% nitrogen gas (N2), representing about 6400kg of N2 above every hectare of land. However, N2 is a stable gas, normally unavailable to plants. Nitrogen fixation, a process by which certain plants "fix" or gather atmospheric N2 and make it biologically available is an underlying pattern in natur.


How to Use NFTs in a System

In the tropics, most of the available nutrients (over 75%) are not in the soil but in the organic matter. In subtropical and tropical forests, nutrients are constantly cycling through the ecosystem.

Aside from enhancing overall fertility by accumulating nitrogen and other nutrients, NFTs establish readily, grow rapidly, and regrow easily from pruning.

They are perfectly suited to jump-start organic matter production on a site, creating an abundant source of nutrient-rich mulch for other plants. Many fast-growing NFTs can be cut back regularly over several years for mulch production.

From Desert to Oasis in 4 Years (Jordan)

Geoff Lawton’s  video in his ever-expanding lineup takes you to Wadi Rum in Jordan where he consulted on a 10 acre organic farm and rebuilt their failing farm into a commercial success.

Wadi Rum looks very much like your classic inhospitable desert region. It was used in the early 1960s as the backdrop set for the David Lean’s masterpiece, “Lawrence of Arabia.”

If you’ve ever watched the movie as Geoff had, you’ll be greeted with a sense of déjà Vu. The place looks familiar and intimidating. Geoff says it still has access to water in the dry Wadi canyons and aquifers.

Geoff Lawton takes you to Wadi Rum in Jordan and shows you how he transformed 10 acres of hostile desert into an abundant oasis, now producing food as a successful organic farm located in the Middle East.
Geoff reveals his design process and explains the steps needed to create a paradise on earth.  
“If we can do it here, we can do it anywhere.” he says.

Geoff Lawton reveals his little known secrets of soil fertility capture using a succession of plants and succulents.

See the amazing results in this 13 minute video. Don’t miss it!

http://www.geofflawton.com/sq/35684-desert-oasis
 


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