It’s important to evaluate all four Rs of fertility collectively when considering the nutrient requirements of your crop. Changing any one R — right time, right place, right rate and right source — can profoundly alter the management of the others, says Dan Orchard, an agronomy specialist with the Canola Council of Canada.
“Adhering to the four Rs as closely as possible will help with the efficiency, environmental issues and, ultimately, the economics of your farm,” says Orchard. “Once you compromise one, it can sometimes change the importance of the others. They’re all synergistic with each other.” The dynamics of all four Rs should be considered when making decisions about fertility, he notes. Not understanding the long-term effects of compromising one or more Rs can put a producer’s crop — and profits — at risk.
For example, the right source may be ammonium sulphate but elemental sulphur is the only product available. “The farmer has already sacrificed the right source if he needs ammonium sulphate and can’t get it. He must now pay more attention to the right place and right time because elemental sulphur should be broadcast in the fall and not incorporated. He’ll also have to increase his rate if he’s not already on the elemental program in order to get the amount of sulphur the crop needs,” says Orchard.
“All of a sudden sacrificing one R really upsets the whole applecart. Sometimes you need to go back to the drawing board when you have to sacrifice one of the Rs,” he says. Such is the case for phosphate, which can be tricky to put in the right place — growers may have to adjust rates to compensate if placement is compromised. “If there’s no way for your equipment to seed-place that 20 pounds of phosphate that’s recommended, you’ll have to up your rates because the right place isn’t there anymore and the rate has to increase,” says Orchard.
He also warns producers to watch their rates of seed-placed phosphate as higher rates could put seed safety at risk. “We hear many agronomists and growers say they don’t necessarily agree with the messaging of only 20 pounds of actual phosphate with the seed. They’ve been getting away with two to three times that rate and not seeing a problem. I understand that can happen when moisture conditions are really good, and with certain openers and equipment, but I challenge them to make sure they’re not burning the seed,” says Orchard. Generally, plants burned by fertilizer do not emerge and other factors, such as seeding too deep, frost or pests, are blamed.
From the Country Guide website: Make more money from fertilizer
Four Rs in action
Orchard recalls an instance when he was asked to provide advice on plot work being done on 2,000 acres of canola. Twice the number of canola plants had emerged in an area accidently seeded without seed-placed fertilizer when compared with the rest of the field. “They were burning about 50 per cent of the seed,” says Orchard. “The plants that did make it out of the ground had ample fertilizer and the farmers were still getting average to above average yields… They then realized they wanted to get the best of both worlds. They wanted to not burn the seed and to get all of that fertilizer there somehow. It’s sometimes surprising how many plants should be there when everything is managed properly.”
A popular trend across the Prairies is to apply most of a fertilizer blend in the band and the remainder with the seed. Phosphate will be beneficial for the seed if levels are low in the soil. However, there is little to gain from potash being placed with canola seed, which is not the case with other crops, such as cereals, says Orchard. “It is much less likely in Prairie soils for canola to respond to seed-placed potash when compared with cereals. (Canola) can mine it better, is not as demanding early on and potash doesn’t have the disease suppression benefits like it does with cereals. It depends on the crop. The four Rs all intertwine and they vary with every situation in every crop. In this situation, the right place isn’t with the seed for canola,” says Orchard.
Be cautious the rate being applied with the seed is not too high. Placement may be too close to the seed, says Orchard. “We need some separation at those higher rates,” he says.
One nutrient your crop may require at higher rates is nitrogen. “If you’re in an area that doesn’t receive as much rainfall as the next, it may be too risky for you to put on these high rates and you’ll choose not to for financial reasons,” says Orchard.
Next best options
Weather and equipment may limit a producer’s ability to adhere to the four Rs. “If you’re out there combining and you’re planning on banding fertilizer in the fall and it snows, you’ve got to sacrifice your timing,” says Orchard. “It’s not like we can always follow the four Rs optimally every single time because there will be limitations, but you have to realize the trade-offs you’re making.”
When compromises must be made, the next best option may be the only alternative. “You might not have the ability to put it in the right place. Your default should be the next best place,” says Orchard. When the next best place is for the fertilizer to be broadcast, the producer can then evaluate the rate, source and timing. “You need to either compensate with some of the other Rs or understand the drawbacks of breaking that R.”
From the various forms of sulphur to coated, slow-release fertilizers, understanding the available products, how they work, their intended uses and their final application purposes is crucial, says Orchard. “There are a lot of products being put on because a producer is going over the field anyway and it’s only four or five bucks; might as well put it on. But it doesn’t matter when you put it on or what product you use or how much you use or where you put it if the crop doesn’t need it.”
Consideration of the dynamics between the four Rs could make increasing the efficiency and economics of your farm.
“Evaluate all four Rs together and how they interact with every situation. It will vary from field to field and day to day. It’s important not to close your eyes, pick a product and put it on whenever it’s convenient for you. It’s more important to evaluate the synergies and benefits of all four Rs being the best you can make them.”