The Agronomists, Ep 3: Christine Brown and Frank Larney on manure management


Some call it stinky, others call it the smell of money, but whatever your thoughts on manure may be, we also know it’s a valuable soil amendment and nutrient source. It’s also a rather tricky one, as manure is highly variable, and requires specific handling to make the most of it.

For this episode of The Agronomists, host Shaun Haney is joined by Christine Brown, with the Ontario Ministry of Agriculture, Food and Rural Affairs, and Frank Larney, with Agriculture and Agri-Food Canada, to talk about how to best use manure, the value it brings to soil, and how to manage losses.

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  • How does one “get into” manure? Well, for Christine Brown, each crop specialist had to have a specialty, Christine was also an animal science graduate, so it just fell into place (she was kind of volun-told)
  • Frank Larney, soil scientist with AAFC, grew up on a mixed (cattle and sheep) farm in Ireland. He has early experiences with cleaning out pens. Background in no-till work, switched to manure management in the 90s
  • Not all manure is created equally. It’s the biggest misconception. Based on livestock type, ration, bedding, storage, water added, age of animals, concentrated rations vs a maintenance diet, determines the quality of manure.
  • Dry, liquid, composted manures: all different as well. Not homogenous. Liquid systems especially rely on the water content. Raw or fresh manure is usually right out of a pen and applied to the field. Compost is a more recent trend, windrowed, composted for 3 to 6 months (a processing step).
  • Testing. Shaun doesn’t remember ever testing manure even though he grew up in a feedyard. TEST!
  • Most of the time, if manure is applied to a field, commercial fertilizer might also have to be applied. There are “book” nutrient values. Don’t underestimate the N content, but there’s most likely more P, and K content. As well as some micronutrients (bonus!).
  • There can be too much of a good thing. Don’t over apply.
  • A composted manure would have more stable nutrient content (varying by livestock species of course). Poultry manure would probably have the most N. Bedding as a factor will also increase the carbon content (the higher the C:N, the longer it’ll take to break down by soil microbes)
  • VIDEO: Jeff Schoenau (cause he also knows his sh$t) Take a number of samples from the manure, preferably before it’s applied, submit to a lab. You’ll get total nutrient content and also maybe a bioavailable nutrient estimate, depending on the lab. Distiller’s grains. Homogeneity when applying. Manure 101
  • Liquid manure is prominent in Ontario. The ratio of ammonium N to organic N in liquid compared to solid is different, says Brown. That changes the way it needs to be managed. If it’s mostly ammonium, and has a high pH, it needs to be incorporated quickly.
  • Here on the prairies, incorporation and no-till don’t really mix together. Maybe on irrigated land. Palliser triangle, manure can be used on that “lighter” (sandier) ground maybe a weight. You will still lose some ammonium through volatilization. Composting can be the solution as the N becomes more stabilized through that process.
  • Most benefit to the grower? Composted or raw manure? Composted has more benefits in the long-term, in terms of stable nutrients, but is more time and labour-consuming. More value in raw, but probably more losses. Economics is probably the biggest reason why someone would apply raw (in Ont.). On the prairies, composted manure can be transported longer distances. Research done at Lethbridge research centre came up with a break-even. Beyond 22 km it wasn’t worth it economically to haul fresh feedlot manure.
  • Quality of compost can be an issue too. Have to be careful with the definition of compost with regards to manure.
  • How effective is lagoon aeration and converting the ammonia to a more stable form? Brown’s not sure about stability, it blows off a lot of that N. Additives to lagoons may only help with odours, but not sure about converting ammonia to a more stable form. Larney deals exclusively with feedlot/solid manure. Liquid systems are a whole other ball of wax.
  • When’s the best time to spread composted manure on hay ground? Springtime between cuts. There’s not really a particular time that’s better than others. Evenness of distribution is important. Have a good spreader. Which fields need it the most? Also have to be careful not to create a compaction issue.
  • anything to watch for when it comes to spreading digestate from a municipal of agricultural digester? Digestate has a high pH. Ammonium will volatilize about ten times higher. Incorporation may be key.
  • High app rates of manure over many years, P will eventually leach (which is kind of shockin, since P is not mobile in soil). Something to be aware of.
  • In-crop applications? Check out this video.
  • Temperature for composting is important, kills off pathogens and weed seeds if temps are high enough.
  • VIDEO: Mario Tenuta. Compost vs raw manure vs liquid and the benefits to farmers. Pasta and a meatball analogy for compost product. Realize that compost addition rates will not meet the needs of N in the crop.
  • Why don’t we see more people composting? Difficult to get numbers, even from Stats Can in terms of how much manure is actually composted. It costs money to turn manure into compost, so economics might be one deterrent. Again, transportation will also be another factor.
  • Does C:N matter for manure? Yes. If it’s solid manure and more than 25:1, that N is not going to be released in time for that crop, and sometimes in the process of breaking down that C, the microbe will “steal” some of that N in the process. Most solid manures in that 15:1 to 20:1. Liquid manures are 3:1, 5:1.
  • How deep should you till in manure? Min till high speed disc or a disc ripper/plow, better to get that manure deep? Get it as evenly distributed into the soil profile as possible, but not too deep. The time of year that manure’s being applied will result in compaction. Even a shallow incorporation will reduce volatilization losses.
  • Adding peat to high carbon bedding? Peat is also high in carbon, so it just adds carbon to carbon, so probably no benefit.
  • Best ROI on solid manure, when deciding which fields to apply to: low fertility, low OM, low CEC? Field with low OM will benefit more. If you can get manure onto eroded knolls, it adds OM. You’ll see a bigger response from (solid) manure by adding to low OM, eroded soils. It comes back to the carbon>microbial activity increasing>better soil aggregates>better structure
  • What if manure is applied in fall compared to spring, does the C:N still have to be close? Solids applied in fall, best nutrient availability in spring. Liquid in the spring, better bioavailability in the fall, but again one more pass over the field will mean compaction (especially in Ont situation)
  • Nutrient value of urine? Ammonium content will be high in urine. Phosphorus is associated with solids, potassium is associated with liquids. Some research done on grazing animals and urine patches and the nutrient release from that situation.
  • What’s the best way to store manure to reduce GHG emissions? When there’s manure or livestock, there will be GHG emissions. Six of one, half a dozen of the other.
  • Separating the N and K (or P) from the manure? The trouble with that is that you’re still left with whatever nutrients are left over. Taking the water out of the manure, concentrating the nutrients might be the best way.
  • In dryland situations (on the Prairies), the opportunities for compaction are quite a bit less, so applying manure and being concerned about compaction might not be such a big issue. Freeze/thaw cycles usually alleviate any compaction issues on the prairies.
  • In Ontario, there’s a lot of interest in trying to reduce compaction, especially early spring. The less wheel traffic, the better.
  • Don’t call manure waste because that has a negative connotation, and manure has value.


Related: In-crop drag hose application gives more bang for your manure buck

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