Soil is more than just dirt, a place where plants put down roots to grow seeds.
It’s a complex ecology, teeming with infinite varieties of flora, fauna, microbes and minerals that provide both the raw materials and machinery to build crops and livestock. It’s a factory floor with a lot of moving parts and we’re starting to rate its performance as an indication of its health.
“Soil is extremely complex, some argue as complex as the human body,” Mario Tenuta, a University of Manitoba soil ecologist, said during this winter’s Manitoba Agronomist Conference. “Vital signs or indicators of how well soil functions are examined much like a doctor’s checkup.”
Tenuta singled out six vital signs by which we can talk about soil health and how Manitoba farmers are improving it. He started with awareness, then organic matter, biological diversity in farming, cover cropping, 4R nutrient management and the challenges put forth by soil-borne diseases. If these parts are meshing properly, a soil can sustain crop production without degrading or harming the environment.
“Let’s begin with the soil health awareness,” he said. “Lots of great improvement, particularly in farmer awareness of soil health with several workshops and events over the past couple of years, and a lot of information and articles in the farm media as well.”
There’s a new focus on soil health on the research side too. The University of Manitoba recently hired a new assistant professor, Xiaopeng Gao. His field of study is nutrient cycling in cropping systems and sustainability.
“We’re looking forward to great things from Xiaopeng and working with NSERC, WGRF and the Fertilizer Canada 4R senior industrial research chair that I lead,” Tenuta said. “We’ll be looking at ways to reduce nitrogen losses and improve agronomic performance using the 4Rs.”
The next vital sign is soil organic matter which, according to Tenuta, is also improving.
“We’ve had great advances over the past few decades in terms of improving soil organic matter levels throughout the western Prairie provinces and also western Manitoba,” he said. “And this is because of our reduced fallow years and also reduced tillage and direct seeding.”
Having said that, there is room for improvement on the Red River Valley clay soils which seem to be losing carbon. Tenuta said that suggests a need to intensify research on clay soils, reduce the tillage and see if producers can grow more and better crops without working the soils as hard. There’s a need to improve the situation in the Red River Valley to improve the structure of our soils there.
If soil is like a human body then, like the body, it takes a number of different organs to make it work. In this case it takes quite a number of different organisms and that means soil biodiversity. One example Tenuta cited were nematode worms and the number of different kinds found in different soils and different crops.
“Potatoes really have the worst nematode assemblage and it’s related with cutting off the higher organisms in the soil food web,” he said. “It’s because of the amount of physical disturbance to the soil as well as low residue. But counter that with tame hay land or native prairie, the nematode assemblage is quite different and actually is excellent in terms of the food web while grain and oilseed crops are intermediate to that.”
Cover cropping is another way to keep all those moving parts working post-harvest. Roots in the ground mean something to feed the soil biota and build soil carbon during the off-season. Tenuta talked about Yvonne Lawley’s research with fall rye.
“After the oats grown here were harvested, fall rye was planted. It was terminated in the spring but we still retained more carbon in the soil. Great benefit,” he said. “We’ve actually lost carbon dioxide without the fall rye.”
He also suggested the need for more farmer involvement here.
“Farmers can do a lot more than we can as a few researchers,” he said. “More soils, more areas, more ears, more brains.”
Feeding the crop is still a big part of growing it and fertilizers are now being seen as a part of soil health too. A nitrogen application that releases as much N2O into the air as into the soil is not healthy. How can producers reduce the losses of both off-gassing and leaching?
“There are things present and on the horizon; we have stabilized nitrogen, controlled release fertilizers such as ESN polymer coated so farmers are using these more and more,” Tenuta said. “They come with a premium but they have advantages in places, in cropping systems and are being used. We are showing that they do reduce environmental losses.”
The last item in the checkup is soil-borne diseases and there might not be enough emphasis on this one. Pathogens such as clubroot, potato early dying and soybean cyst nematode are relatively new so we find ourselves playing catch-up.
“But there are a few really good things that have improved recently,” Tenuta said. “One of them is our ability to survey and monitor pathogen dispersal and emerging diseases and pests. Through our monitoring emphasis we’re able to catch soybean cyst nematode really early and I think that’s a good thing because we’re able to manage this nasty pest.”