MINOT, N.D. – Mention Brazilian agriculture and it likely provokes a mental image of vast fields of genetically modified soybeans and large tracts of cattle pastures.
In reality, however, Brazilian farmers are world leaders when it comes to cover crops and conservation agriculture, says Theodor Friedrich, a sustainable farming specialist with the United Nations’ Food and Agriculture Organization.
“We have sent many (students) down to Brazil, seeing how their entire system, and community, has changed,” said Friedrich, who estimated 70 percent of farmers in southern Brazil practice conservation agriculture.
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“The interlinkage of farming, community and science … is very nicely developed.”
Zero tillage and cover crops such as sorghum and the forage grass brachiaria to rejuvenate the soil have rapidly expanded in Brazil in the last two decades.
Joao Carlos de Moraes Sa, a professor of soil science at Ponta Grossa State University in Brazil, said these techniques have caught on because conventional tillage in tropical climates leads to rapid losses in soil organic matter.
In a presentation at the Manitoba-North Dakota Zero Tillage Farmers Association annual workshop held in Minot last week, Joao Carlos, who goes by the name Juca Sa, referred to test results showing that conventionally tilled soil in Brazil loses 35 percent of its organic matter over a five year period.
In comparison, conventional tillage in the Saskatoon area causes soil organic matter to decline 48 percent over 50 years.
The rates of organic matter depletion are much higher in tropical zones, partly because of double cropping but also because higher temperatures accelerate biological processes.
“In the tropical (zone), the speed is like a Ferrari,” said Juca Sa, who showed a slide that measured the soil temperatures of two adjacent fields on Jan. 14, one of the hottest days of the year in Brazil.
Without crop residue, the soil temperature in the conventionally tilled field rose to 63 C, while the temperature in the field with 3.7 tons of residue per acre peaked at 33 C.
He said cover crops can also restore the amount of soil organic matter, making the land more resistant to drought, improving nutrient retention and boosting agronomic productivity.
Juca Sa said farmers need to recognize the benefit of cover crops.
“I’m convinced that we have to put down this concept that we are corn growers or soybean growers or cotton growers,” he said.
“If you talk about food growing, it means you have to introduce into your system other species … that combine to make a result that benefits the main crop.”
Martin Entz, a plant science professor at the University of Manitoba who also spoke in Minot, appreciated Juca Sa’s focus on the value of integration in farming practices.
“We can talk about diversification, but that’s just, ‘if that fails, well that might help me,’ ” he said.
“But integration is about having the different parts of the farming system synergize with each other.”
