An Agriculture and Agri-Food Canada researcher has launched a study to find out whether Jumpstart really works.
Ramona Mohr will be examining how the phosphate-solubilizing seed inoculant containing the naturally occurring fungi Penicillium bilaii, will affect growth, P uptake, yield and quality of canola at the MZTRA farm, and a handful of other sites in Manitoba and Saskatchewan.
“This organism releases organic acids that acidify the area around it, and it solubilizes calcium phosphate, for example, and makes it more available to the plant,” said Mohr, adding that past studies have found it to be effective in increasing P uptake, vegetative growth, and sometimes yields.
Although it has been available under various commercial names since the 1980s, very little scientific data is available on its effectiveness with canola.
In areas with a phosphorus response, meaning relatively low P levels in the soil, one study found a five per cent yield boost.
“If they added 10 pounds of P205 plus the inoculant, it was equivalent to adding a rate of about 20 pounds of P205 per acre as fertilizer,” said Mohr.
Three questions arise when considering using Jumpstart, she added. One is based on whether it is better to simply add P to the system, or use the inoculant to free up more from the existing soil bank. Another is related to economic return on investment in either fertilizer or P. bilaii. The other is whether it can work with seed treatments used.
The plots will look at seed row-placed or side-banded monoammonium phosphate with Liberty Link hybrid 5440. As the study is in its first year, no data is yet available.
According to University of Manitoba Professor Don Flaten, Manitoba soils contain a rough average of 1,000 pounds of mineral phosphorus per acre. A high-yielding canola crop may remove up to 40 pounds each year, all of which comes from the very small portion which becomes available to plants via natural biological processes or in the form of supplementary P fertilizer.
At the Glenlea research farm, organic and conventional comparison trials have shown that some organic systems that rely on legumes for nitrogen can exhibit clear reductions in soil phosphorus availability within as little as 10 years.
“We started off in that Glenlea study with very high phosphorus levels, much higher than the average Manitoba farm,” said Flaten. “They are relying on legumes for the nitrogen, but where is the phosphorus supposed to come from?”
P. bilaii may be used to make farming viable at low available P soil test level of 15 ppm, he added, but once it falls below 10 ppm, the shortage inhibits yield.
“If you’re harvesting 40 pounds per acre, you’ll have to put on
40 pounds per acre, otherwise you’re on your way to exhausting the soil,” said Flaten.
The MZTRA study is among several at the farm exploring sustainable nutrient management.
Rhizobia-inoculated legumes are being used to grab nitrogen from the limitless reservoir known as the sky and put it into the soil, and more diverse rotations and grazing livestock are being tested for their efficacy in reducing the need for glyphosate, which for years has been the foundation of no-till practices.
But looming phosphorus depletion is a brick wall in the form of Justus von Liebig’s famous “law of the minimum.”
Way back in the 1800s, the German chemist and “father of the fertilizer industry” showed that plant development is always limited by the one nutrient in shortest supply. Nitrogen can be constantly replenished by adding legume crops to the rotation, but the available phosphorus in the soil is carted away in the grain that is harvested each growing season.
Over time, yields fall, unless the depletion curve is arrested. That’s because the essential nutrient for the development of strong bones and teeth in humans is also required for plant cell walls and energy-capturing processes.
In the Far East, the “Farmers of Forty Centuries” solved this problem by laboriously hauling “night soil” back to their fields from the cities and villages.
While Europeans were emptying bedpans from upper-storey windows into the street, during Japan’s isolationist Edo period from 1603-1867, with virtually no trade with the outside world, landlords in that country regarded the contents of their tenants’ latrines as a valuable revenue stream, and disputes over ownership reportedly occurred.
At present, solving the problem of phosphorus depletion in agricultural soils has been accomplished by spreading livestock manure, and mining and processing phosphate rock deposits into chemical fertilizer inputs.
Municipal sewage sludge is also spread, but there are concerns over heavy metal contamination.
There are obvious problems with those strategies, however. Mining has obvious limitations on a finite planet, and using livestock manure robs Peter to pay Paul, because the hayfields eventually need to be resupplied with phosphorus, too.
Until the phosphorus loop between city sewers and rural fields is closed, achieving the goal of truly sustainable farming is out of reach. [email protected]