Selecting the right nitrogen type, amount, placement and timing is a challenging part of crop planning each spring. When fertilizer prices are a bit lower, as they are now, it may be tempting to just up the numbers a bit without actually knowing what your fields need to maximize crop production.
By putting some thought into your options now and making sure you have the right plan, you’ll fare better come harvest.
Every seed has enough nitrogen inside it to get out of the ground, but soon after it needs help. “When canola germinates it has enough nitrogen to get it to the cotyledon leaf stage. But by the time it starts to capture the energy of the sun, the seed has usually run out of nutrients and it starts to depend on the soil,” says Ross McKenzie, agronomy research scientist with Alberta Agriculture.
When all nutrients are considered, nitrogen contributes the most to yield says Ray Dowbenko, corporate agronomist with Agrium, the makers of ESN. To determine the right rate of nitrogen to apply, start with a soil test. Knowing how much you need will help you maximize yield.
“Usually the first dollar you spend on fertilizer is going to return you at least $10 or $15 in yield. You want to put on enough that the last dollar you spend still returns you $2. It’s a challenge to predict when that will be, because it really depends on moisture conditions during the growing season,” McKenzie says.
TIMING IS CRITICAL
Application timing options include nitrogen applied in the fall, early spring, at seeding or in crop. While the options are pretty broad, picking the right one is really important. Fall banding can be effective and it reduces spring workload. Banding early in the spring is also an option, but with more drawbacks. “When you band before you seed, you compromise seedbed condition and dry out the soil,” says McKenzie.
Putting fertilizer in during the seeding operation is definitely the most efficient option time-wise, but conventional fertilizer has to be placed a safe distance from the seed to avoid damaging it. “The ideal situation is to provide a controlled supply of nitrogen during the period of maximum crop uptake,” says Dowbenko.
To ensure the fertilizer will be there when the crop needs it, look for a nitrogen source that releases in a controlled way. New enhanced efficiency fertilizer products, such as Environmentally Smart Nitrogen (ESN), are safer to apply with the seed. ESN has a controlled release polymer coating that allows it to be placed right in the seedrow in greater quantity than with conventional nitrogen sources.
“ESN allows you to put three to four times more nitrogen with the seed versus standard urea. Normal urea releases quite quickly, and changes into ammonia which is toxic to seedlings. If it’s coated with the polymer coating, it releases much more slowly into the soil,” says McKenzie.
The release of nitrogen from ESN is controlled by soil temperature and moisture level, which also determine crop growth and nutrient demand. “As the soil warms, the nitrogen solution moves through the coating faster, just when the crop’s need for nutrition increases,” says Dowbenko. “ESN maximizes efficiency of uptake by the crop; it can reduce application costs and provide higher yield compared to conventional nitrogen.”
Choosing a controlled release nitrogen source can also prevent environmental losses. Nitrogen is lost when it moves downward through the soil (leaching) or when it converts to gasses which escape into the atmosphere (denitrification and volatilization). Both types of nitrogen loss are potentially harmful to the environment. Enhanced efficiency fertilizers have been shown to reduce losses to groundwater by as much as 50 per cent and losses to the air by 30 per cent to 50 per cent, according to a study published by International Plant Nutrition (www.ipni.net).
There are also ways to boost nitrogen after the crop has emerged, but they’re not highly recommended. “Farmers are always interested in top dressing afterward, but it’s not very efficient,” says McKenzie. “And I rarely recommend foliar application because leaves are designed to take in the energy of the sun, not to take in nitrogen.”
In general, broadcast fertilizer applications are more prone to environmental loss than banded application.
SELECT ING THE BEST PLACEMENT
Fertilizer placement is the biggest single factor in successful uptake of nutrients by the plant. The nitrogen has to be where plant roots are growing when they need it. Yet conventional fertilizer can’t be placed too near the seed except in small quantities.
“Place ESN with the seed or band urea a little away from the seed,” suggests McKenzie. “Ideally, place it a bit lower than the seed — about three inches deep with canola. That way it will stay in moist soil for a bit longer, and the plant roots will find that band as they grow, proliferate around it, and can take that fertilizer up quite efficiently.”
McKenzie and Dowbenko have both been actively researching the efficiency of ESN in a variety of crops over the last few years. “We just wrapped up a three year program with Agriculture Canada at Melfort, Saskatchewan,” says Dowbenko. “We were looking at ESN on canola and wheat, and we had very good results. The ESN has done exactly what it is supposed to over the course of three years.”
McKenzie’s work with ESN in canola is ongoing. A recently completed report on ESN in winter wheat concluded that ESN has excellent potential for seed-placement in spring seeded crops, and results with seed-placed and banded ESN in winter wheat were very positive. “There are two key benefits of ESN,” says McKenzie. “First, you can place more with the seed. Second, if you run into a wet spring it can help reduce nitrogen losses, which are greater in areas with heavier precipitation.”
There are other ways to consider getting nitrogen to your crop, McKenzie says. Some farmers consider incorporating residue, which allows microorganisms to break it down into nutrients. But, says McKenzie, leaving the trash on the surface has more important benefits. “From a soil conservation standpoint, we’re better to leave the plant residue on the surface to protect the soil from erosion. It also provides a mulch layer to reduce evaporation and moisture loss, and helps to reduce the emergence of weeds.”
Adding a pulse crop to the rotation is an effective alternative. Peas and lentils fix their own nitrogen so no application is required. “Even including a pulse crop in the rotation every third year is going to have an economic benefit, so why not take advantage of that free nitrogen?” says McKenzie. Also, the amount of nitrogen applied can be reduced in the crop following most pulse crops, which results in further economic benefit.
A third option is to apply heavy manure every four years. “It can reduce the amount of nitrogen fertilizer we need and may actually eliminate the need for phosphate fertilizer depending on the rates,” McKenzie adds.
Robin Galey is a freelance writer and editor based at Calgary, Alta.