As piggery projects are on the rise, some researchers and watershed organizations consider it crucial to review the rules in place to limit damage to waterways. The concentration of farms in the same area as well as the amount of real phosphorus leached – two essential variables – are not currently taken into account by Quebec.
Despite some improvements in recent years, the overwhelming majority of rivers in agricultural areas still have worrying phosphorus levels. Animal manure spread on fields — including pig manure — is the main source of this element.
The duty indeed reported on Saturday that the number of piggeries being created or expanding has increased since 2018, according to the number of authorizations granted by the Ministry of the Environment and the Fight against Climate Change (MELCC).
In return, citizen opposition is also more felt. It often crystallizes around environmental issues, notably the quality of water in agricultural areas.
Pigs produce manure rich in phosphorus, which must be spread on a cultivated area. A certain amount of absorption of this phosphorus is theoretically determined for each field, depending on the soil and the plants growing there.
These quantities are evaluated and monitored in an agro-environmental fertilization plan (PAEF) and in the phosphorus report that farms must submit to the MELCC each year.
But the actual “leakage” to the river system is not monitored. “The problem, when determining the quantity of phosphorus that can be put in the fields, is that we look at the inputs, but we don’t look at what comes out”, explains Stéphane Campeau, specialist in watersheds and aquatic systems at the University of Quebec at Trois-Rivières.
There is therefore a mismatch between what is determined by an agronomist in a PAEF and what actually happens in waterways. “We have to change the paradigm,” believes Mr. Campeau.
“Soils are like sponges, they have a certain capacity to absorb phosphorus. The excess accumulates in the soil and, when this accumulation reaches significant levels, there is an emission,” summarizes Aubert Michaud, now a researcher associated with the Missisquoi Bay watershed organization. He spent 25 years at the Institute for Research and Development in Agro-Environment (IRDA), studying in particular these “flows” of phosphorus from fields to watersheds.
Soils are like sponges, they have a certain capacity to absorb phosphorus. The excess accumulates in the soil and, when this accumulation reaches significant levels, there is an emission.
Poor water quality
“All rural water bodies are vulnerable. There is clearly a dynamic of contribution [de phosphore] supplement in areas of intensive livestock production”, continues the specialist.
The phenomenon greatly contributes to the eutrophication of waterways and the appearance of cyanobacteria.
Quebec is “especially not” in a situation “where we can afford to increase phosphorus in waterways,” says Mr. Campeau.
Certain practices have improved in recent years, such as the addition of riparian strips, a sort of buffer between soil and rivers. The quantity of surplus phosphorus has thus decreased, but “the trend towards accumulation has not been reversed in most watersheds,” points out Jean-Olivier Goyette, postdoctoral researcher at Laval University.
A study he conducted and published in Nature Geoscience in 2018 showed that watersheds in agricultural areas would need 1000 to 1500 years without phosphorus input to fully recover their health, because of this accumulation.
“We are therefore far from having reached a satisfactory level, especially in the small rivers. This phosphorus level is two to three times too high, often even ten times too high in the spring,” says Mr. Campeau.
Quebec recognizes this frankly in its 2020 State of Water Resources and Aquatic Ecosystems Report. From 22 watercourses selected in agricultural areas, the MELCC noted that the vast majority of monitoring stations almost always presented samples exceeding a critical phosphorus level for the protection of aquatic life.
To phosphorus are added nitrates and pesticides: overall, the water quality threshold is still far away, say these three researchers.
Piecemeal approach
It is also the concentration of animal breeding, including pigs, in certain territories that remains in a blind spot. The MELCC evaluates each building or pig project separately: for three buildings of 3,999 pigs presented by the same breeder, for example, the ministry issues three authorizations separately.
“If you just assess what’s happening in separate plots, but ignore the rest, you’re missing a certain picture,” says Mr. Goyette. “The piecemeal aspect of project authorization is indeed worrying,” believes Aubert Michaud.
However, the land is drained towards the same watershed: the most relevant scale for this problem, according to all the researchers consulted.
In waterways that exceed water quality criteria, including 0.03 mg/litre of phosphorus, “there needs to be a moratorium on the development of the hog industry,” says Campeau.
Mr. Michaud proposes that, in the concentration zones, the input into the fields be limited, in particular by requiring the separation of the solid part of the pig manure from the liquid part. This would allow “more à la carte” enrichment and therefore less likely to be in surplus, also notes Stéphane Godbout, researcher at IRDA.
Several technologies, such as “V-shaped scrapers” or centrifuges, already make it possible to separate the liquid from the solid.
The obligation to bury quickly in the ground, by turning it over or by injection, could also be part of the framework measures, he adds.
Soil erosion must also “be absolutely controlled,” says Michaud. Land can be protected by rotating away from the common corn-soybean duo, green manures or winter cover crops. Finally, the land must be developed in such a way that it respects the riparian strips.
Three solutions, three front lines for the environment, “and three support levers” concludes Mr. Michaud. Costs are linked to these measures, but the “externalities on the environment” must be taken into consideration in the price of pork or in financial assistance programs, also suggests Mr. Campeau.