Nitrogen is colorless, odorless and tasteless, but all life on earth depends on it. Without it, our bodies cannot synthesize the nucleic acids that make up our DNA, or the protein-forming amino acids that are the very building blocks of our cells. Problematically, atmospheric nitrogen is relatively inert or nonreactive.
Growing maize crops alongside legume trees has been shown to naturally fertilize fields and increase crop yields in many parts of sub-Saharan Africa. As a region known for its extremely volatile climate and it’s population facing global hunger issues, this discovery is extremely important for the future of agroforestry in the area.
In a study published in the Agronomy Journal by researchers at the World Agroforestry Center, researchers compared yield stability in three scenarios: maize intercropped with the nitrogen-fixing legume tree Gliricidia, continuously cropped monoculture maize receiving inorganic fertilizer, and the typical practice of resource-poor farmers who grow maize without any external input.
Results show that while mono cropping practices produce a high yield crop, it is not the sustainable solution in the long run. Instead, the research suggests that by strategically combining small doses of inorganic fertilizer through an intercropping system, maize yields will be more stable and will not only increase, but will lead to other ecosystem services like soil stability, water storage capacity and overall fertility.
The increased productivity is due to Gliricidia, which can “fix” nitrogen by taking it from the air and transforming it into a medium that plants can use for their own growth. Once leaves are shed, the organic matter is also released back into the soil. This alleviates the need for manufactured nitrogen fertilizers.
“Growing maize with legume trees has increased yields in many parts of sub-Saharan Africa,” said Gudeta Sileshi, the lead scientist on the study and regional representative for ICRAF’s Southern Africa Program. “Now we know this is not just a temporary phenomenon. For maize farmers who can’t afford fertilizers, agroforestry with nitrogen-fixing trees offers a stable increase in production, allowing them to feed their families and replenish the soil.”
Fertilizers are important to this region because the systems are prone to widespread land degradation and extreme weather events associated with climate change.
Consequently, the research will lead to policy debates about agricultural development in Africa since agricultural policies often emphasize intensification of inorganic fertilizer use. However, without addition of organic matter, the high yields obtained with inorganic fertilizer may not be sustainable.
“To grow their way out of poverty, Africa’s small-scale farmers don’t just need a good harvest for one or two years, they need long-term stable, high-yield harvests,” said coauthor Akinnifesi, former regional coordinator for the World Agroforestry Centre, Southern Africa Regional Programme. “Moreover, they need to know which farming systems will be both stable and sustainable.”
Brown Mang Onwuka
A large-scale research and development project has shown that giving farmers resources and advice on nitrogen fixation through legume plants can double yields and boost incomes in Africa.
Continue reading Nitrogen fixation helps double some African farm yields