Investigating biofertilizer
by Treena Hein
Ecological agriculture may be the key to reducing reliance on fertilizer
WHAT IF YOU could rely less on costly commercial fertilizer and more on Mother Nature to help make your soil the ideal environment for growing corn?
The solution, says Dr. George Lazarovits a plant pathologist at Agriculture and Agri-Food Canada’s (AAFC) Southern Crop Protection and Food Research Centre in London, Ontario, is “ecological agriculture “ – a fundamental reform of agriculture, moving towards technologies and practices that rely significantly less on fossil fuels and more on naturally occurring solutions.
“Ecological agriculture relies on greater application of place-specific knowledge of soils, microorganisms, weather, water, and interactions between plants, animals, and humans,” he says. “It aims to build soil structure, thus reducing the need for large quantities of chemical fertilizers, pesticides, and water. It also aims to eliminate and even reverse soil erosion and land degradation.”
Ecological agriculture is beneficial for other reasons too. First, it builds up the organic matter of soils, thereby sequestering fossil fuel emissions into the ground. It also creates healthy topsoil rich in beneficial microbes, which in turn provide higher yields with a reduced need for costly inputs such as nitrogen and phosphorus.
Most importantly for Lazarovits’ research, “many soilborne bacteria can fix elemental nitrogen and release phosphorous from the soil, thereby making these nutrients available to roots,” he says. “Such microorganisms have been widely used for a long time in Brazil to minimize fertilizer use while maximizing yield of sugarcane for the ethanol industry.” In addition to reducing input costs, these soil bacteria – also called biofertilizers – provide sugarcane plants with greater stress tolerance and promote lower plant disease pressure.
“In North America, micro-organisms are widely used for legumes but not for other crop species,” says Lazarovits. “We need a greater understanding of how plants other than legumes derive more of their fertilizer needs from
such microorganisms.”
In the case of corn, most of these beneficial ‘endophytic’ associations have likely been lost over the many decades of plant breeding. However, Lazarovits sees great potential for these associations to be recovered, enhanced and used on a large scale if associated research is completed.
“We have identified several root-associated microorganisms from Ontario-grown corn that appear to enhance the growth of corn through nitrogen fixation,” he says, “but the mode of action must be determined.”
Solving this mystery begins with, among other things, a close examination of what’s happening in sugarcane. “Corn and sugarcane are closely related genetically, and may have the same relationships with microbes inside the roots,” Lazarovits says. “Of the four new species of bacteria we’ve isolated from corn roots, two are similar to ones used for growing sugarcane.”
Studies in Ontario and Quebec with AAFC scientist Danielle Prevost are focusing on proving conclusively that nitrogen fixation is occurring in corn at the root level and measuring the extent that this process improves plant growth, says Lazarovits. Soil samples from 24 Ontario and Quebec farms have so far been taken in order to determine what types and how many nitrogen-fixing bacteria exist.
The researchers have been developing genetic probes to rapidly identify the presence of such bacteria on roots so that they can identify the extent of such interactions and what practices promote or deter their activity. Lazarovits anticipates that this technology will significantly increase the pace of development of biologically-based fertilizers for corn. “We intend to collect a consortium of strains that can be used to improve microbial nitrogen fixation in Canadian soils,” he says.
In addition, a collaborative project with Dr. Manish Raizada at the University of Guelph (funded by OMAFRA) is examining whether corn in other places – mostly ancient corn varieties from Mexico – interact with the same soil bacteria as Ontario corn does. Over a hundred bacteria have been isolated from inside such corn seeds, but what they do to plant growth has not
been determined.
The overall research will eventually provide much-needed information to Ontario growers interested in adopting soil microbial inoculants to reduce their fertilizer costs. “We are as yet unsure how these bacteria should be best delivered to the corn plant,” Lazarovits says. “It could be through direct soil application or through inoculating seed.”
Determining which cropping systems and practices (such as crop rotations) promote the presence of large populations of beneficial soil microorganisms is another area that must be researched, says Lazarovits. “Following these recommended rotations should help improve root health and plant performance under stress from climate and disease.”