Trees in Crop Fields — Boosting a Farm’s Natural Economy

by Laura Crothers last modified Oct 23, 2017 04:09 PM

 

The mid-afternoon sun beats down on the dry earth as Elleman Mumba walks under the cool shade of his musangu trees—tall 8-year-old trees that he has planted in wide rows in the middle of the fields where he grows maize and other annual crops for food and sale.

Mr. Mumba is one of a growing number of farmers across Zambia and other southern African countries who are bucking the conventional wisdom that planting trees in crop fields creates competition with the standing crop for sunlight, water, and nutrients. 

But Mr. Munba’s trees, Faidherbia albida —native plants known locally as “musangu”—are rather unusual in how they fit into the farm.

Not only are Faidherbia trees leguminous, and thus capture nitrogen gas from the air and make it usable for themselves and surrounding plants, they also lose their leaves and go dormant during the summer rainy season, when most small-scale farmers plant their maize crop. They leaf out during the dry season, just when livestock are most in need of precious fodder and when the fallow fields would otherwise be baking in the sun.

Research and farmers’ experience have documented maize yields doubling or tripling underneath the Faidherbia canopy, demonstrating the substantial boost to soil fertility attributable to these trees. This is significant in a country where many farmers cannot afford enough fertilizer and where maize yields average under 1 ton/acre.

What can we learn from the Zambian agroforestry system in California, where farmers can usually afford the fertilizer needed to produce much higher yields, whether they are growing feed corn, vegetables, or perennial fruit crops?

These Zambian farmers are successfully designing cropping systems that are more adept than their previous monocrops at harnessing natural processes that directly benefit crop production. They are putting in place a more complex natural economy where biological organisms—trees, bacteria, and crop plants—do the work of exchanging goods and services like nitrogen and organic matter to the ultimate benefit of the farmer.

This system replaces a simpler one that is more reliant on the work of the farmer and the money economy, as well as on fossil fuels and the pollution inherent in their use, to sustain desired production.  

Such designs are usually not one-size-fits-all. Even in Zambia, farmers with sandier soils have more difficulty establishing Faidherbia trees. 

However, regionally-specific and scale-appropriate systems that accomplish more of the work of farming through natural processes are well worth exploring in all parts of the globe.

 

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