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Conservation agriculture with trees increases crop yields, builds soil organic matter, improves farmers’ income and strengthens their resilience to environmental stresses. These factors make conservation agriculture more acceptable to smallholder farmers, especially those in hilly areas, says Dr Agustin Mercado Jr.
Speaking at the First International Agroforestry Congress in Bohol, the Philippines, Dr Agustin Mercado Jr said that in Brazil, Argentina, US, Australia, Cambodia and other countries, flat land covered more than 200 million hectares. Yet in the Philippines alone, sloping land occupies more than 10 million hectares.
Deliberate integration of trees is needed on sloping land, he argued, especially since of the 3 million hectares under corn in the Philippines, 2.6 million are sloping, which exacerbates erosion and ultimately reduces yields. Managing the 10 million hectares of Philippine uplands is a challenging task. The soils are inherently acidic and poor in nutrients, particularly lacking in phosphorus. These areas also experience more than 2500 mm of rainfall per year, thus, soil erosion is high.
Whatsmore, erosion from traditional up-and-down-the-slope cultivation—rather than along contours—is 30 times greater than the generally accepted ‘tolerable’ soil loss of 12 tonnes per hectare per year.
All of these characteristics, combined with inappropriate farming practices and deforestation in upper areas of watersheds, have led to a decline in farm productivity and increases in poverty and malnutrition.
The outlook is bleak not only for the uplands but also for the lowlands, since activities in upland communities affect the lives and livelihoods of the people downstream.
However, Dr Mercado has evidence that conservation agriculture with trees on sloping lands could help. According to him, this kind of agriculture is a dynamic and ecologically-based sustainable land management system that diversifies and increases production while at the same time promoting social, economic and environmental services for all land users.
The five important principles of conservation agriculture with trees on sloping lands are: 1) minimal soil disturbance; 2) continuous mulch or ground cover; 3) diverse crop species; 4) integration of trees; and 5) integrated water, nutrient and pest management.
Minimal soil disturbance reduces, if not eliminates, damage to the soil structure. Continuous ground cover protects the soil from drying and eroding. Integrated nutrient and pest management strategies are better established when above- and belowground resources are optimized through diverse crop species. A study by Dr Paningbatan from the University of the Philippines Los Baños indicated that soil erosion by water and air is eliminated when soil cover is greater than 30%. Farming along the contour produces 40 tonnes of soil eroded per hectare per year. Whilst this figure is a significant reduction from up-and-down cultivation, it is still beyond the tolerable soil loss. Conservation agriculture with trees uses hedgerow intercropping systems and other techniques that reduce erosion and surface runoff while increasing water quality and stream flows.
The Conservation Agriculture with Trees training centre at the World Agroforestry Centre’s research site in Claveria, Mindanao, the Philippines, researches different conservation agriculture systems, rainwater harvesting, vermiculture and rubber agroforestry systems, among others. These provide the basis and evidence for expanding conservation agriculture with trees throughout the Philippines and other areas in Southeast Asia that have similar characteristics.
Dr Mercado and his team hope that the Claveria research site will offer an example of better management practices for the 10 million hectares of sloping land in the Philippines and the 181 million hectares in Southeast Asia.
This work is linked to the CGIAR Research Program on Forests, Trees and Agroforestry