Tania Holembovska is content manager at EOS Data Analytics, based in Menlo Park, California, US. The views expressed in this guest article are the author’s own and do not necessarily represent those of AFN.
Agroforestry is the joint cultivation of trees and crops in the same area. Trees are planted in strictly oriented rows: in the northern hemisphere, along the meridians to minimize shadow; closer to the equator, they’re planted perpendicularly, for additional shade – where it is a valuable resource. Between the rows of trees, crops usually grown in fields are planted – including cereals, herbs, vegetables, and berries, among others.
The effectiveness of agroforestry lies in the fact that trees protect crops from the wind, retain moisture, prevent soil erosion, and provide natural organic fertilizer and mulch when leaves fall. Leaf mulch is true permaculture: mulching happens on its own, and there is no need to import hay, removing organic matter from other places.
On top of that, soil moisture measurement performed on agroforestry sites proves that correct selection of trees stops plants from competing for moisture. This is thanks to the trees’ ability to control soil moisture content naturally. Basically, it comes down to the selection of species with a taproot or fibrous root system.
Microsoft, Rabobank announce first round of carbon credits with agroforestry startup reNature – read more here
Sunlight in agroforestry sites is slightly lower than in open fields, but other favorable factors — and the direct profit possible from trees in the form of nuts, honey, and other produce — increase the yield from the site overall. The presence of trees also multiplies the number of bird species that destroy insect pests.
Here are five of the main ways in which agroforestry can benefit farming operations – and the land they reside on.
1. Recovery of degraded lands
Gradual land deterioration occurs due to unsustainable agricultural practices. The UN Food and Agriculture Organization estimates that over 40% of rangelands and 20% of cropping lands are degraded, with Sub-Saharan Africa having the highest rate of land degradation.
Agroforestry can mitigate this through an increase in vegetation coverage. Trees help hold the soil together, presenting an underestimated but simple solution to the disastrous consequences of soil erosion caused by traditional farming methods. Fallen leaves and bark keep the soil moist by forming a protective layer of mulch and later replenishing the soil with nutrients as they decompose. Controlled pruning of tree leaves can be an additional soil enrichment method. Tree roots remove toxins from the soil and control soil acidity and salinity, balancing them as needed. Nitrogen-fixing trees additionally aid in the growth of food crops by maintaining soil fertility all year round.
2. Soil moisture conservation and water quality enhancement
Trees in agroforestry sites help conserve soil moisture thanks to mulching, leading to higher crop yields. Soil moisture is always higher under trees than in open areas. Agroforestry increases soil infiltration characteristics, trapping water and increasing soil moisture levels.
On top of that, agroforestry enables water quality improvement. Deep-rooted trees used in agroforestry sites act as filters, consuming the excess nutrients applied in the crop field and reducing groundwater pollution.
3. Mitigation of soil erosion
Soil erosion is a natural process. However, agricultural practices accelerate erosion beyond a point where lasting damage is caused.
The rate at which soil erosion occurs depends mainly on vegetative cover. The less vegetation, the harder the soil begins to crumble. And bare soil stays completely unprotected from wind and rainfall.
In agroforestry, forest canopy offers the necessary protection of soil against erosion, stopping wind and rain from adversely impacting the land – while mulch helps conserve moisture, which further protects against erosion.
4. Soil fertility improvement
Soil fertility can be increased by planting nitrogen-fixing tree species between rows of cultivated plants. The foliage of many tree species can be harvested to provide green manure to crops that provide nutrients, prevent soil erosion and water loss, and deter pests.
Agroforestry has already proved its effectiveness in enriching soil organic carbon, and improving soil fertility and nutrient availability, due to the presence of trees in the system which enhance soil microbial dynamics.
5. Improved water supplies
Due to alarming rates of deforestation, land increasingly deteriorates through misuse, which means water supplies suffer. Degradation limits the soil’s storage capacity, leading to decreased water content in dry seasons and floods in wet seasons. When soil is covered with vegetation, as it is in agroforestry sites, it acts like a sponge, storing water that is used by crops and trees or released into lakes and rivers through groundwater, improving water supplies and water quality in general.
Ultimately, the implementation of agroforestry is an excellent approach to improve soil health, water quality, and food security in a world which is concerned with adapting to, and mitigating, the impact of climate change.