Sonja Fransen and Patrick Handyside, both with Agriculture and Agri-Food Canada, volunteered to illustrate some of the benefits of soil life activity with these rubber castings of actual wormholes supplied by soil management specialist Anne Verhallen.
Unfortunately, organic matter levels in Ontario soils continue to decline in many areas
By Jeffrey Carter
March 13, 2019 - While there are many benefits to increasing organic matter levels in agricultural soils, promoting the idea can be a challenging proposition.
Anne Verhallen in her role as soil management specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs has been pitching the idea for years, most recently at the Ontario Fruit and Vegetable Convention in Niagara Falls on February 20.
“When I graduated from school, I had the idea you could turn a cover crop over and get organic matter. That’s not exactly how it works. It’s the microbiology that makes the organic matter,” Verhallen said.
It’s not that cover crops are unimportant to building stable organic matter levels in soils. In fact, there’s growing evidence – including work conducted by University of Guelph research Laura Van Eerd – that long-term rotations that include cover crops can lead to small increases of the stable portion of organic matter over time.
However, cover crops are just part of a systems approach which include other practices like no-till, the addition of manure or compost to soils and broader crop rotations.
Unfortunately, organic matter levels in Ontario soils continue to decline in many areas.
Verhallen cited Essex, Lambton and Chatham-Kent as one example. Research shows that from 2002 to 2016, levels fell on average by 0.8 per cent. That’s a decline of 16,000 pounds per acre.
The loss reduces the nutrient recycling ability of soils and soil aggregate stability. Healthy soils with adequate levels of organic matter and aggregate stability are less likely to erode after a heavy rainfall since their capacity to hold water is enhanced. That’s also important during drought conditions.
Aggregate stability is also important in managing compaction. Verhallen said tractors and other equipment used in orchards are often lighter compared to field operations but there’s likely more traffic.
That was confirmed by a farmer in the audience who said each of the alleyways in his orchard likely sees a tractor’s pass 40 to 50 times a year.
Adequate levels of organic matter are also important to soil life, including earthworms. In orchards, earthworms pull fallen leaves into their burrows which can lower disease pressure on the soil surface and recycle nutrients, Verhallen said.
There are often competing interests in primary agriculture. While soil health is an important consideration for farmers, including tree fruit producers, profitability is often the first consideration and building organic matter comes with a cost.
The two speakers who followed Verhallen during the morning session didn’t talk about organic matter but instead focused on labour-saving orchard designs.
“As labour becomes more expensive, we need our management simplified for the labour we have,” Gregory Lang, a researcher with Michigan State University, said.
High-density orchards require less man hours for management and harvest operations. They also involve the use of grown on dwarf rootstocks which, according to Gregory Lang with Michigan State University, require more in the way of irrigation with fertigated water since their root systems explore significantly less of the soil profile where they would otherwise access more of their required nutrients.