Aguas negras: An agricultural revolutions buds in Mexico

Just outside Mexico City, a group of farmers who grow maize and other crops using sewage water are adopting cutting-edge conservation agriculture techniques to save on irrigation and reduce their costs.

Geraldo Gálvez Orozco is a man with wrinkles as deep as his voice and hair that is decidedly neither gray nor white. After concluding his 40-year career as a math professor Gálvez went looking for a new challenge and found it in farming.

Gálvez is a 79-year-old Hidalgo native who has been farming in the Mezquital Valley for 15 years. The valley is nestled in the rolling mountains of southwest Hidalgo State, situated 60 kilometers north of the country’s capital, Mexico City. It is a region known for many things; the Mezquital trees that canvas its hills, an arid climate, and surprisingly, a thriving agricultural sector. Despite the region’s parched soils—the Mezquital Valley receives an average of only 527 mm of rainfall each year— about half of the valley’s residents are farmers.

Putting waste to work

Since 1789, Hidalgo’s farmers have relied heavily on an unusual form of irrigation—wastewater from Mexico City. The valley’s farmers use the sewage water, referred to as ‘aguas negras’ or black water, to irrigate 563 square kilometers of grain. It is the largest wastewater-irrigation system in the world.

Using sewage water to irrigate food crops may raise the suspicions of some, but 10% of the world’s crops are irrigated using some form of sewage, according to the IRC International Water and Sanitation Centre. Farmers in India, China, Pakistan, Jordan, and Israel apply the practice. Wastewater is spiked with nutrients or ‘natural fertilizers’, so crops are enriched without the added cost of fertilizer. Precautions are taken to ensure the crops irrigated by the aguas negras are of the highest quality. By Mexican law, farmers can only use sewage water to irrigate cereal and fodder crops. Maize and alfalfa are the most popular.

Adopting in the face of change

Today, the farmers of the Mezquital Valley are facing change. Within the next two years, the black water irrigation supply will decrease due to a new government initiative to purify Mexico City’s wastewater and reuse it within city limits.

To reduce their water use and maintain their soils, farmers in Hidalgo are switching from traditional agriculture practices to an innovative way of farming that is used extensively in Argentina, Australia, Brazil, Canada, and the USA.

From arithmetic to agronomy

Gálvez started experimenting with conservation agriculture-based practices eight years ago when he heard of its benefits from a fellow farmer. He began by trying zero-tillage, a practice whereby crops are seeded directly into field residues without plowing, and a key proponent of resource-conserving farm practices. Today, on the three-hectare farm where Gálvez grows maize and oats, maize husks and cobs litter the ground. Husks and cobs that assure any curious passer-bys that Gálvez indeed practices conservation agriculture, as leaving crop residue is another foundational principle.

“Since switching to conservation agriculture, I have noticed a small increase in my yields compared to what I used to produce under irrigation, but I don’t do it for the yields. Living in a climate like this, keeping my soils in good condition is my number one priority,” Gálvez says, “that’s why I practice conservation agriculture.”

According to Fermín Hernández Méndez, a graduate of CIMMYT’s conservation agriculture-certification course and a technician with the Mexican subsidiary of Monsanto, ASGROW seed company, Gálvez isn’t the only farmer in Hidalgo changing his ways. “In Hidalgo, conservation agriculture is a revolution,” said Hernández, “Farmers are adopting the practice because they know that a change is coming— a change that is most likely going to strain their soils.”

For soil’s sake

It can be seen in the Mezquital Valley, as well as around the globe, that farmers who have practiced traditional agriculture for generations are adopting conservation agriculture. This is because today, more than ever before, global changes are threatening agriculture and food security worldwide.

Climate change, drought, soil degradation, and a rapidly growing populace are taking effect, and traditional farming practices can’t keep up. In the face of this adversity, farmers are switching to sustainable farming practices –practices that use fewer resources, facilitate healthy, nutrient-rich soils, and improve farmers’ yields.

Conservation agriculture is a forward-thinking way of farming based on three principles: minimum soil movement, covering the soil surface with crop residues and/or living plants, using crop rotations to avoid the build-up of pests and diseases. These principles are widely adaptable and can be used for a variety of different crops in varied soil types and environments.

Sustainable and beneficial

Mezquital Valley farmers receive record yields due to their nutrient-rich irrigation system. Farmers in Mexico’s highlands – where crops rely on precipitation alone – are not so lucky, but because of conservation agriculture’s water-saving benefits, these farmers have produced acceptable yields in dry years when neighboring fields withered. During the 2009 drought in the Central Highlands, farmers who practiced conservation agriculture harvested up to 125% more maize than those who farmed the traditional way.

Other attractive benefits of conservation agriculture are its cost and labor savings. Reducing or eliminating plowing allows farmers to sow and fertilize a field in a single sweep, rather than multiple passes. Decreasing machinery use saves time, fuel, money, and wear and tear on machinery.

Combining higher yields with lower costs, conservation agriculture allows farmers in rainfed areas to earn more and save more. This meant an average net return that was almost twice as high as the earnings of traditional practitioners. The average net return of Mexican highlands farmers who practice conservation agriculture was more than 800 USD per hectare compared to the approximate 400 USD per hectare that conventional highlands farmers reaped. It is no secret that conservation agriculture is putting more money in farmers’ pockets and more food in mouths around the world.

A smooth transition

Although the benefits of conservation agriculture are numerous, its adoption worldwide faces hurdles. One is the competition for crop residues, which often have great value as forage. Also, farmers are skeptical about shifting from the traditional farming method, including tillage, which they and their peers have practiced for generations.

As a conservation agriculture-certified technician, Hernández works to help smooth the transition. “It’s nothing more than a question of culture,” he replied, when asked why some farmers are hesitant to adopt the new principles. “It’s not that they don’t believe us or think we mean ill, it’s simply that they are afraid of change.”

Yet these hurdles begin to appear less daunting as farmers face rising temperatures, sky-rocketing fuel prices, and looming water shortages, not to mention mounting demands to grow more food grains locally, rather than importing them. To help farmers, researchers are exploring and promoting flexible ways to apply conservation agriculture. For instance, they suggest that farmers keep a minimum of 30% ground cover year-round. The remaining residues can be used or sold as forage. The new system also opens opportunities for more diversified cropping, including growing fodder crops, which can provide additional income for farmers.

Patience paying off

“I’m not worried for myself, I have all I need. I am worried for my children. The land needs to stay healthy and fertile for the future generations,” Gálvez says as his shoes, one step behind his wooden cane, crunch through the corn husks and stalks that blanket his fields. The air is dry and the sun is searing, yet Gálvez’s crops seem at home in their arid environment.