Brazil has been a major pioneer of the technique since the country adopted it in the 1970s. But its small farmers have been lagging behind, mainly hindered by the high costs of specialized planting machines needed for ZT.
Now, thanks to cheaper seeding machines and efforts by farming organizations and individual agronomists, small farmers are spreading the word.
ZT Boom
Essentially, ZT consists of seeding uncultivated soil, as well as rotating crops and constantly covering the soil with crop residues (the parts that remain in the field after harvest).
Preventing the soil from being bare has several advantages. It protects the land from heavy rain, leaves cleaner surface waters and helps recharge aquifers – permeable stone layers that supply much of the world’s water.
It also cuts soil erosion by up to 90%, allowing for 30-60% greater rainfall infiltration so less water is needed for irrigation.
In addition, crop residues boost the soil’s organic content and help fix carbon in it. so that ZT reduces carbon dioxide emissions far more than conventional techniques.
"With the best systems you have over a ton of carbon sequestered [in the soil] per hectare per year. When you consider there are a hundred million hectares under ZT in the world, this is an awful lot of carbon dioxide taken out of the atmosphere," says British agronomist John Landers, who has promoted the technology in Brazil since the 1970s.
Today, after the United States, Brazil has the second largest area cultivated using ZT – some 25.5 million hectares, or more than 60% of the country’s cultivated surface. Although ZT was initially tested in the United Kingdom, it was the United States who adopted and further developed it in the early 1960s.
The practice was first introduced to Brazil to combat soil erosion. In 1972, Herbert Batz was the first farmer to import ZT-adapted seeding machines in Latin America. "He encouraged me and other neighbors to do the same," recalls Manoel Henrique Pereira, a pioneer of ZT adoption in Brazil.
Farmer-to-farmer word of mouth then fueled ZT’s spread throughout Brazil – there was little reliance on government subsidies. In 1979, the creation of a farmers’ club to further the technology was the first step of many. There are now nearly 50 such clubs in Brazil, led by the National Federation of Zero Tillage into Crop Residues (FEBRAPDP).
But the real ZT boom came in the 1990s. The area farmed using the technique reached a million hectares in 1991 – 2.6% of Brazil’s cultivated area at the time – and has been growing exponentially ever since.
Between 1991 and 2004, Brazil increased its grain production from 57.8 million tons to 125 million tons from a cultivated area of 42 million hectares, 22 million of which was under ZT.
This is also the period ZT began to gain favor in the Brazilian central savannahs – the cerrado.
Savior of Savannahs and Forests
While ZT was easy to apply in the humid subtropical southern states, where winter rains allow two harvests a year, the arid cerrado posed a greater challenge. The six-month dry season allows only one annual harvest, which halves the amount of grass and crop residues available to cover the soil.
The problem was solved by growing a tropical pasture alongside the main crop. Following the harvest, this grass is used to feed farm animals. When the rainy season returns, the grass is killed by herbicides and used to cover the soil where the next crop is planted. According to Landers, the herbicides used in ZT (mainly glyphosate) are among the most environment-friendly available.
The result is that soils severely eroded by years of grazing, and usually abandoned, can now be used to grow pasture again – and without any fertilizer.
"We have 16 million hectares of pasture in the cerrado, 70% of which are degraded. Now we can plant good maize or soybean crops on these and go back to top quality pastures after three years, which is a real breakthrough," says Landers, who founded the Zero Tillage Association for the Cerrado Region (APDC).
Meanwhile, in the heart of the cerrado, a team from the French International Cooperation Center for Agronomic Research (CIRAD) has been leading key work in adapting ZT technology for dry regions. The team has, for instance showed the benefits of planting a certain grass species (Brachiaria ruziziensis) alongside the main crop. As well as being easier than other species used as crop residues to control with herbicides, its long roots – up to two meters – allow it to take up more groundwater.
Introducing ZT to the cerrado has also slowed down deforestation, as farmers are less likely to cut down trees to open up new pastures.
"ZT has saved the cerrado," says CIRAD agronomist Serge Bouzinac. "If it hadn’t been adopted, this region would have become a huge pasture and many farmers would have extended the deforestation frontier in the Amazon even further."
Spreading ZT
But ZT requires an investment from the farmer, who needs to buy specialized machines for planting and spreading the fertilizer on cover crops. As a result, small farmers have been left out of the ZT boom, and remain an important challenge for its spread.
In 2005, according to FEBRAPDP, small farmers used ZT on 600,000 hectares, while medium and large farmers applied it to 24.9 million hectares.
This might be changing, however, thanks to increasingly cheaper manual and animal-powered planting machines, as well as projects to train farmers. An initiative by APDC expects to teach ZT techniques to as many as 38,500 small farmers in the cerrado.
John Landers considers the initiative a success, with over 150 field demonstrations and 480 technicians trained so far.
"Farmers are accepting this animal traction technology because they all have horses or oxen, and this makes them independent instead of having to wait for the neighbor’s tractor to prepare land and plant for them," he says. "This way they plant earlier, harvest more, renovate their pasture at the same time and don’t have to pay third parties for tractor hire."
A greater challenge would be to aim for the global spread of ZT. According to data gathered by German agronomist Rolf Derpsch, who has promoted ZT in South America since the 1970s, 47% of the area cultivated using ZT in the world is in South America – mainly Brazil, Argentina and Paraguay. Another 39% is in North America, 9% in Australia and only 3.9% is in the rest of the world.
Brazilian farmers and researchers have an important role to play in spreading the word. People like Manoel Henrique Pereira have done so for years, travelling worldwide to share their experience and technical advice. "I have been to over 20 countries to promote ZT adoption," says Pereira, whose next destination is Laos.
CIRAD is also spreading its technology to small farmers abroad, notably in Cameroon, Cambodia and Vietnam. "Brazil has much to show other developing countries," says Derpsch. "I’m convinced that [ZT] can be very effectively used in South-South cooperation."
The technology is expanding in Bangladesh, India, Nepal and Pakistan where 1.9 million hectares are currently cultivated using ZT – with great potential to save huge amounts of irrigation water.
Africa, however, is another story. The use of crop residues as cattle feed remains an obstacle, as this does not leave enough grass available for use in ZT. This problem will have to be solved if the technique is to be adopted in African nations.
But above all, adopting ZT requires open-mindedness, says Derpsch. "The mindset is the main barrier to no-till adoption in countries where deep-rooted traditions hinder the abandonment of tillage and the plough."
SciDev.Net