Getting to know your manure a little better is worth the effort, says nutrient management specialist Trevor Wallace.
And the first thing to know is that no two loads are the same.
“Understand that you’re not dealing with a nice consistent product or a nice standard product,” the Alberta Agriculture specialist told attendees at FarmTech. “This makes it a little harder to work with.”
Fields with low amounts of organic matter benefit the most from manure application, but it needs to be done properly. That means knowing soil fertility levels and the nutrient levels in the manure, which vary with the type of animal producing the manure, their rations and supplements, and even the weather (because rainfall and evaporation rates affect manure stored in lagoons).
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Manure, unlike most fertilizers, contains both organic and inorganic forms of nutrients, said Wallace. Plants can use inorganic forms of nutrients immediately, while organic components must first abe broken down into their inorganic forms. Nutrient imbalances can also be a challenge as crops need five to seven times more nitrogen than phosphorus. However, most manure contains equal amounts of nitrogen and phosphorus, or a double amount of nitrogen to phosphorus.
If straight manure is applied to crops, a producer will often be applying more phosphorus than needed. Wallace advised producers to take a manure sample when they are getting ready to spread.
“Use the sample to plan next year’s application and to supplement the fertilizer,” he said. “You’re always sampling for a year late, but it’s a good way to measure what you’re doing. You can’t figure out how much to apply until you figure out what’s in it. If you know what’s in it, you can plan better. If you know the nutrient content, you know how to manage it.”
Knowing the nutrient content can help target the manure to the crop to be grown.
Another factor to be aware of is that nitrogen loss begins the minute the manure falls out of the animal, and a great deal is lost through spreading. But it’s not hard to know when that happens as ammonia odour results.
“If we can change how we are spreading it, we can save more of the nitrogen and help with that imbalance,” said Wallace.
Timing is important, and manure should be applied as close to when the crop needs it as possible, said Wallace.
“We’d like to spray everything in the spring, but that’s not logistically possible,” he said.
“There are other options, like putting manure on in summer on forages, putting it on in the fall, and putting winter wheat in front of it,” he said.
Application is determined by the consistency of the manure being applied and the type of farming to be done. Solid manure can be applied with a vertical auger, which has an even and consistent spreading pattern to break up lumps.
Liquid manure
There are more options for applying liquid manure. Injecting manure requires a lot of power, which can be a deterrent. This method can involve using a shank injector or a disc injector. A disc injector saves nitrogen and results in less loss compared to broadcast systems.
General surface broadcasting is cheap and fast, but increases nitrogen loss and produces a lot of odour, said Wallace.
“If you put it up in the air in a nice big arc, you get a lot of air moving through it and you get a lot of nitrogen loss,” he said.
Depending on conditions, anywhere from 20 to 80 per cent is lost. When it is warmer and drier, more nitrogen will be lost.
Surface banding is a good compromise between injection and general broadcast because it reduces odour and nitrogen loss, but does not require as much power as injection. Knowing the amount of ammonia can help a producer decide how to spread it. Surface broadcasting, which uses splash plates or hoses, reduces nitrogen loss and uses the nutrients more efficiently. Injectionbased methods are the best for preserving nitrogen content, and can result in only a five per cent loss if the manure is injected properly.
Manure has to touch the soil, said Wallace. Ammonia nitrogen has a positive charge, while soil has a negative charge.
“If we get them to touch, there’s less of a chance that it will gas off or evaporate,” he said, adding plant material is neutral, so nitrogen does not stay bound to it.
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“Understandthatyou’renotdealingwithaniceconsistentproductoranicestandardproduct.Thismakesitalittlehardertoworkwith.”
TREVOR WALLACE
NUTRIENT MANAGEMENT SPECIALIST
