Farmers spend big bucks on fertilizer — about $3.6 billion on fertilizer and lime in 2010 alone, according to Statistics Canada. With that kind of cash it pays to put those nutrients where they make a difference: the rooting zone of your crops. The key is to remember what the fertilizer industry calls the 4Rs: the right nutrients, applied at the right rate, at the right time, in the right place.
Payoffs can be significant. Using nutrients, including fertilizers, manures and composts, crop rotations and cover crops more effectively will stretch dollars, boost yields, promote more resilient crops from healthier soils and minimize pollution and greenhouse gases.
Careful use of nutrients doesn’t just save money, says Jim Boak, “farmer in residence” with Canadian implement maker Salford Group. “It’s a way to make money — to make you more profitable.”
“We’re talking about (soil) conservation and sustainability, and nutrient management and soil health is part of that conversation,” he adds. “We have the ability and knowledge and resources to be regenerative, to build the soil and improve it considerably.”
The right nutrients
Plants depend on a range of “foods,” the big three being nitrogen (N), phosphorus (P) and potassium (K). Other significant elements include sulphur, calcium, magnesium and an array of “micronutrients” including zinc, manganese, copper, iron, boron and chloride.
Soils differ not only in the nutrients, but in whether the environment is sour (acidic) or sweet (alkaline), as measured in the pH balance. If a soil is too acidic, for example, applying lime will help nudge it towards a more neutral pH, improving its structure and freeing nutrients previously locked away under acidic conditions.
What’s the best way to determine the nutrient profile of your field? Start with a basic soil test. For about $30, a basic test tracks P, K and sometimes N, micronutrients, pH, organic matter and Cation Exchange Capacity (CEC), the soil’s ability to hold and release elements and compounds, including nutrients). As a bonus, the test offers a crop-specific prescription for additional nutrients to optimize yields or build and maintain fertility.
Prepare a sample for testing by collecting 12-15 soil cores per field (more is always better) drawn at random from representative areas. (Avoid oddball zones such as dead furrows, headlands or sandy knolls that give false results.) Break up and mix the cores in a clean, stainless steel or plastic pail, seal a handful of earth in a plastic sandwich bag, and ship it to a lab accredited to provide soil tests in your province or region.
“Soil testing is very regional, with different provinces having different soil test methods,” says Jack Legg, branch manager and agronomist with the SGS Agri-Food Laboratories in Guelph, Ont. Variations in soil type, depth, pH range, climate and farm practices across Canada mean it’s crucial to ensure your lab provides the appropriate test and recommendations for your area.
The gold standard is to test every field, every year, particularly if you’re testing for nitrogen. If that’s too ambitious, try sampling fields at least every three years for more stable nutrients such as phosphorus and potassium, or before rotating into a new crop.
If you’re happy with your lab, stick with it. Using the same lab should mean more consistent testing — and better tracking of fertility trends over decades. “It’s like taking the car to the same mechanic, or always going to the same dentist,” says Mitchell Timmerman, Agri-Ecosystem specialist with Manitoba Agriculture. “They know you. They’ve got your files. They know your history.”
The right rate
There are two main approaches to plant nutrition: “crop sufficiency” and “build and maintain.”
Crop sufficiency applies enough fertilizer to make up for the nutrients the optimal yield of your crop removes in a season. It works particularly well for nitrogen, because N tends not to stick around from one year to the next. A shape-shifter among the elements, nitrogen transforms from solid to gas or leaches away in water as a nitrate. Because N levels can fluctuate over weeks or months, most approaches — especially in warmer, wetter provinces where N is less stable — reflect crop sufficiency.
More stable nutrients, such as potassium and phosphorus can be applied to build and maintain an optimal level of fertility. Ontario, for example, recommends maintaining hayfields and pastures at 12-30 parts per million (ppm) for P, and 120-250 ppm for K. Once you reach these levels, there’s no economic advantage to adding more.
With phosphorus, Manitoba Agriculture’s Mitchell Tim- merman recommends a hybrid approach, building P into a mid range, and then topping it up or drawing it down as finances allow. “That puts farmers in a good place, agronomically and economically,” he says. “The need for fertilizer in any given year is not critical. So, if prices are high, you can back off for a year without compromising yield potential.”
The right type
A Javelin fertilzer spreader offers adjustment options that simpler cone spreaders do not, but they may not be viable for very small farms.
For a small farmer, the most economical fertilizer choice is whatever works with your existing implements (if you have them.) As consulting agronomist Doug Higginson, of Vancouver Island’s Top Shelf Feeds says, farmers tend to “work with what they’ve got.” For most producers, that’s equipment that spreads dry granular fertilizer.
There are other options. Many corn growers favour liquid “starter” fertilizer, or a compressed nitrogenous gas called anhydrous ammonia as a relatively inexpensive source of N. But those products tend to be more for the guys cropping thousands of acres, rather than dozens, or even a few hundred.
While liquid and anhydrous require specialized equipment (and anhydrous is hazardous if not correctly stored and applied) granular is relatively easy to store if it’s kept covered and dry. Granular is readily avail- able, and there’s no shortage of new and used implements to spread it. If you don’t already own a spreader, a few hundred to a thousand bucks at an auction could net you a basic three-point-hitch spinner-type spreader, or a decent conventional seed drill that allows fertilizing with or near the seed.
While you’re fertilizer shopping, consider whether premium-priced “enhanced efficiency” or coated nitrogen products might be worth the extra cash. These newfangled products use inhibitors or coatings to reduce the loss of N, or delay its release until conditions for plant growth are more favourable.
Higginson has seen growers apply coated N with corn at planting time to avoid side-dressing additional nitrogen later. This summer he’ll work with another farmer to broadcast coated N on grass, with the goal of extended fertilization from a single application.
These fertilizers cost more — $946 per tonne for 40-0-0, with 50 percent of the granules polymer- coated, versus $673 for conventional 40-0-0 — but they may pay off in reduced N losses, better yields, and lower operating and labour costs from fewer passes in the field.
When it comes to fertilizing, Higginson says soil health should be the main aim. “The best way to look at chemical fertilizers is as a supplement,” he says. By combining nutrients from different sources to boost soil organic matter and microbial life, commercial fertilizers can be applied “in balance with the organic sources of nutrients you’re bringing in.”
The right time
Feeding a crop is a little like shoveling food to teenager; the best time for chow is when they’re hungry. (Then again, when are they not hungry?) For plants, this comes during the growing season when the soil is warm (or about to warm), soil microbes are active and crops are either actively growing, or on the cusp of germination and rapid growth.
The payoff is better nutrient use, even for tricky elements like N. Manitoba research indicates that when N is broadcast and worked in during the autumn, for example, only 40 percent of it sticks around to be used by the crop the following spring. But if N is broadcast in the spring, at least half is available for crop use. Weather plays a factor, too. Waterlogged soils, floods, and major downpours can trigger nutrient losses. Throwing fertilizer on dry ground during a drought also guarantees it will sit there, rather than reach the rooting zone.
For producers with broadcast spreaders, the best time to apply is with spring tillage, or on the surface, just before sustained and gentle rains. Manitoba Agriculture’s Mitchell Timmerman likens it to watering a fertilized garden. Would you rather use a watering can that breaks the water into drops for a gentle soaking, or just splash a bucket of water on the ground?
The right place
The most efficient place for nutrients is in the rooting zone where plants have easy access to available food. The problem is it’s not always easy to get those fertilizers into the soil in a timely fashion, and without damaging the crops you’re trying to help.
One solution, if you have the right drill or planter, is to piggyback fertilizer application onto seeding, applying at least a portion of the fertilizer with the seed, or “banding” it in the rooting zone near the seed.
But even here there are limits. Germinating roots can be burned by the salts in nitrogen and potash, so farmers must either limit the N and P planted with the seed, or “sideband” those nutrients a couple of inches to the side of the seeds. Ontario, for example, does not recommend planting corn and applying urea N (46-0-0) with the seed. But if you’re banding it five centimeters to the side or below the seed kernels, you can apply up to 40 kg per hectare. (Crops differ in their tolerance, so it’s important to check rates for each crop and soil type.)
Because only limited amounts of fertilizer can be ap- plied at planting, farmers may face the problem of either shorting low-fertility fields, or finding another way to get more fertilizer into those hungry soils. The conventional approach is to broadcast and then incorporate the fertilizer with spring tillage. In other cases, “if you’ve got soils that really need the fertility and you are building it up, then broadcasting into a crop is your safest method” to avoid nutrient loss, says Ontario Ministry of Agriculture, Food and Rural Affairs nutrient management specialist, Christine Brown.
The key is to broadcast during the active growing season, rather than when the crop is dormant, so that rainfall, soil microbes and insects, including earthworms, can team up to shift nutrients towards the roots. “There isn’t one perfect approach that works for every situation,” Brown adds. “But if you know what the intent is — getting the nutrients to the roots and keeping them out of watercourses — you can factor that into your management.”
Spreader calibration and maintenance
When it comes to maintenance, the key is thoroughly washing and then lubricating implements after use.
“There are very few fertilizer products that are not corrosive, and that includes compost, biosolids, bloodmeal, pelletized chicken litter. Even lime and gypsum develop dust and attract moisture and get in cracks and seams,” says Salford’s Jim Boak.
“The very first thing you want to do is make sure that equipment is cleaned right way. Keep it painted. When you’re done, oil it or repaint it. Keep it clean and well maintained. Use lots of water, lots of oil, grease, and paint.”
The other factor is regular calibration. The traditional quick-and-dirty field method involves estimating the application rate from the area it takes for your spreader to apply a known weight of fertilizer. But this is really just a rule of thumb. The best approach is to read the manual and the labels on the implement, and calibrate as per the manufacture’s instructions, including following instructions for ground speed, adjustments for different granule densities, and the degree of overlap suggested for consistent coverage. (As a general rule, air-driven and drop-box spreaders are easier to clean and calibrate than spinner-type bulk spreaders.)
Check spreader width by laying out containers (such as evenly-sized cake pans) in equal increments across the area the spreader can cover, then operating the implement in a pass over the containers. The traditional approach is to lay out pans on both side of the spreader, but BBI dual-spinner bulk spreaders marketed by Salford, for example, require outside-edge testing: the operator lays out the pans on one side of the unit only, spreads into them, and then returns to make a second pass on the opposite side, spreading in the same direction. Emptying each pan into a test tube or graduated cylinder and then lining them up in order provides a visual read on spread width and relative distribution.
“If you don’t calibrate between one product and another you will not apply the correct rate,” Boak says. “If you can’t afford to take the time, you can’t afford to farm. You’re wasting money, number one. And number two: you’re putting the soil health and environment at risk, and that’s a risk to yourself, too."
Reading the fertilizer label
Fertilizer labels feature three (or occasionally four) numbers, representing nitrogen, potassium (listed as phosphoric acid, or P205) and soluble potash (K20). (If there’s a fourth number, it represents sulphur, or S.)
Example: Granular urea, 46-0-0. The product is 46 percent nitrogen by weight, with zero phosphoric acid (P205) and zero soluble potash (K20).
Monoammonium Phosphate (MAP), 11-52-0. Eleven percent N, 52 percent P205, zero percent K20.
Fertilizing for the future
Large farms are already using variable rate technology to precisely apply the right fertilizer in the right area. The key is to combine detailed computerized maps of soil nutrients with GPS-guided equipment to put more fertilizer where it’s needed, while trimming output in zones with higher fertility.
But can this approach work on farms with hundreds of acres, rather than thousands?
The answer is a qualified yes now, and a more certain yes in the future as costs fall and the approach becomes standard, says Jim Boak, of Canadian implement maker the Salford Group. Key components include soil mapping (for $13 an acre, Ontario’s SGS Agri-Food Labs will grid-test fields and generate soil test results and recommendations for each 2.5-acre plot), yield monitoring, GPS guidance, and equipment with hydraulic controls permitting variable rate applications.
The whole package is likely to be in the mid-five figures, but Boak expects prices to fall as the technology becomes more established, and as some pro- grams migrate onto smartphone-style platforms.
For a small spreader that aligns with the new high-tech approach, Boak suggests budgeting about $20,000 for a three-point hitch air-delivered unit with a 15-foot boom, suitable for banding or fertilizer. For a new variable rate bulk spreader, the bill rises to about $30,000.
On the plus side, Boak says precise use of fertil- izer, coupled with other soil-building efforts (manure, good rotations, forages and cover crops) could trim the fertilizer bill by up to 40 per cent. “If you’re a young guy renting land, even with 250-300 acres you can make it pay on that small patch.”
- Ray Ford