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Maintaining soil productivity during climate change


November 30, 1999
By Dan Woolley

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Attendees at the 2011 Scotia Horticultural Congress received a brief overview of what climate change in the Maritimes could do to their soils and what they might do to adapt.

Attendees at the 2011 Scotia Horticultural Congress received a brief overview of what climate change in the Maritimes could do to their soils and what they might do to adapt.


Dr. Derek Lynch, the Nova Scotia Agricultural College’s Canadian Research Chair in organic agriculture, says soil and climate are intimately linked together as climate is one of the five factors driving the types of soils the Atlantic region has.

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Soil plays a major role in determining climate through the loss of methane and nitrogen to the atmosphere, noted Dr. Lynch, who is predicting warmer, longer growing seasons, greater warming in the summer, and warmer, more open winters.

He also predicts wetter seasons but greater seasonal variations year to year, with a potential for drier summer conditions. There will also be more extreme weather events with greater climatic variability across Atlantic Canada, which will influence the regional distribution of crops, he added.

The greater frequency of weather extremes will impact soil functions, said Dr. Lynch, with more droughts requiring more irrigation and on-farm water storage. More extreme rainstorms will also mean more soil erosion, nutrient leaching and the need to look at planting more cover crops.

Growers will also have to look at improving soil quality and adding organic matter to increase the resiliency of their soils, he said, adding this process is an important component of ecosystem resilience. Soil provides a service to an ecosystem by decomposing dead matter and removing contaminants, said Dr. Lynch. The water supply, therefore, is regulated and protected by the soil ecosystem, which stores water, plant nutrients and carbon.

Warmer conditions, he observed, will increase soil biodiversity, with increased organic matter decay and nutrient mineralization.

A wetter climate will increase leaching potential, said Dr. Lynch, noting more weather variability means more frequent extreme events with more drought and more erosion, including more open winters when most leaching occurs.

Increasing soil organic matter will increase water-holding capacity and the soil’s hydraulic conductivity, he said, thus reducing the risk of erosion and protecting against extreme rainfalls, while removing contaminants from ground water. Composting will also help retain soil moisture.

Climate change, by altering soil temperature and moisture, can result in changes to the crops raised in an area and their productivity, said Dr. Lynch. It can also change the rate of organic matter composting and the quality and quantity of the soil’s organic substrate. These processes combine to alter the rate of organic matter production, he said.

As a result, he believes there will be a greater focus in future on the shoulder seasons of seeding and harvesting. Many of the impacts on soil organic matter happen during the fall as a result of freezing and thawing and nutrient loss in the fall can be prevented with cover crops and increasing organic matter to increase carbon sequestration to reduce CO2 emissions and improve soil quality.

“Eastern Canadian soils sequester less carbon than Western Canadian soil because we lose less organic matter over time … because of our traditional forage based cropping systems and our cooler seasons,” said Dr. Lynch.

He recommends increasing carbon in the soil, increasing forage in the rotations and, perhaps, reduced tillage. Better tools are also needed to monitor the soil’s biological status to determine if organic matter is degrading or aggrading, the rates of nutrient release and if biodiversity is being sustained.

One of the more effective strategies to adapt to climate change will be to increase soil resiliency through increased organic matter and increased carbon storage, said Dr. Lynch.

He also sees a need to promote cropping systems that will increase carbon storage because production systems that sustain soil biodiversity will be more robust and resistant to the impact of climate change.