Turf & Rec

Features Agronomy
There is much to keep in mind when choosing a fertilizer type


March 24, 2009
By Mike Jiggens


Topics

thumb_lyonsCHOOSING between a synthetic and organic fertilizer isn’t as simple as merely wishing to take a more environmentally-friendly approach toward turf care.


Dr. Eric Lyons, a plant nutritionist with the University of Guelph, examined the key differences between the two fertilizer types during an address he made in Toronto in January at the Ontario Golf Superintendents’ Association-sponsored Golf Course Management Conference and Trade Show.

When selecting one type of fertilizer over another, it’s important to compare “apples with apples and oranges with oranges,” he said.

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A key consideration to be made is that “nitrogen is king” in turfgrass, Lyons said. “Don’t ever forget that. Nitrogen drives turf growth rates. Nitrogen drives turf recovery rates.”

Most organics, he said, are low in nitrogen yet are high in phosphorus, particularly with hog and poultry manures.

“If you’re putting down as much nitrogen fertilizer as you need with an organic, you’re probably overapplying phosphorus exponentially.”

Too much phosphorus works against the perceived environmentally-beneficial attributes of organics due to the concern that the nutrient can wreak havoc with our waterways. Lyons noted a law exists in Pennsylvania which prohibits farmers from applying manure on their fields based on the nitrogen requirements of the crop.

“Farmers can only apply manures based on phosphorus requirements. If they do it based on nitrogen, they’re overapplying phosphorus.”

About “99.99 per cent of the time,” the plant doesn’t care where its nitrogen comes from, whether it’s from an organic source or one which is inorganic from a synthetic process, Lyons said, adding the microbes in the soil might care as may the golf course superintendent.

“I’m one of the few people who works in turfgrass nutrition who learned it from the plant’s point of view. Most people who work in turfgrass nutrition are soil fertility experts. They study the soil and the nutrients in the soil. I study the plant and the nutrients in the plant.”

If a superintendent is considering the use of an organic fertilizer, it’s up to him to decide whether or not it’s truly in the spirit of organics, suggesting there is no definition for referral.

Organic fertilizers include manures, plant products and mined nutrient sources. The mechanism of release of an organic fertilizer is through microbial activity.

“Microbes in the soil eat the carbon that’s contained. They need it for energy, and there’s more than enough nitrogen around in that compound. So they release that nitrogen into the soil and then the plant can take up the nitrogen.”

The warmer the temperature, the faster the microbes work “which is good because typically you want more nitrogen when it’s 25 (degrees Celsius) out than when it’s 5 out.”

Organic fertilizer use has been deemed a holistic approach to fertilization because it’s the soil that’s being fed rather than the plant itself.

When soil is tilled, oxygen is being introduced, giving microbes a better chance to break down more carbon. In traditional agriculture, soil carbon is something farmers are trying to put back into the soil.

Another reason for organic fertilizer use is that a full nutrient spectrum is covered.

Things that come from organisms are generally considered to be organic in nature. The United States Department of Agriculture defines an organic product as one which is the product of an organic method. The USDA doesn’t consider Milorganite to be organic due to the method in which it’s made because it’s made from human waste or sewage sludge, even though it is a carbon-containing compound and is the product of animal and plant waste.

Organic chemistry is a study of carbon-containing compounds, and most who are employed in that particular field work with petroleum products. Lyons said petroleum products are nothing more than plant products which have been buried underground for a long time. These carbon-containing compounds all used to belong to an organism, and this is where the term “organic” originates, he said.

The carbon-to-nitrogen ratio must be considered in an organic fertilizer, Lyons said.

“If you have too much carbon and you add too much carbon to your soil, now, all of a sudden, the microbes don’t need carbon anymore. They need nitrogen.”

When the microbes have sufficient carbon, they’ll grab up nitrogen, he said.

Leaf litter compost available from municipal sites had typically contained other debris, including twigs and garbage items. It also had a high carbon-to-nitrogen ratio which was usually so high that when applied, it reduced the amount of available nitrogen to the plant. Even though organic matter may be added to the soil, “you’re definitely taking away nitrogen.”

Lyons said that’s usually more of an agricultural issue because, with turf, a little more nitrogen is always being supplemented.

Occasionally, undesirable ingredients beyond debris are found in organic fertilizer sources, including heavy metals. “You can buy manure from the farmer down the road, and you’re not sure what’s in that.”

If one is to choose an organic fertilizer, it’s helpful to buy from a local source.

“If you’re buying an organic fertilizer that was made in Delaware or one made in northern California, and we use fossil fuels to ship it all the way to Ontario, are we really living by the organic mantra? No, we’re not because it’s about keeping nutrients in the landscape that they are. Most people don’t know that.”

Other organic fertilizers, such as corn gluten meal, may contain pre-emergent herbicidal properties. Lyons said it’s probably not a good idea to be using corn gluten meal as a fertilizer when overseeding.

Several advances have occurred with synthetic fertilizers since they first came on the market in the early 1900s. Originally, they provided a quick flush of growth, but slow-release has since been developed to ensure a steady growth rate with better plant uptake and lower amounts of nitrogen needed in a growing season.

Perhaps the most significant difference between synthetic and organic fertilizers is that the percentage of nitrogen in a synthetic is comparatively higher. A 46-0-0 synthetic fertilizer is 46 per cent nitrogen. If a true organic fertilizer hasn’t been “spiked” with a synthetic nitrogen source, “you will rarely see nitrogen levels above 10 per cent.” Anything above 10 per cent likely won’t be a true organic fertilizer, Lyons said.

The cost per bag of asynthetic fertilizer can be relatively high, especially with slow release. With organic fertilizers, the cost per bag is variable and depends on where the organic comes from. A bag packed in Delaware and shipped to British Columbia will be expensive, yet a truckload of manure from a local farmer will be cheap or perhaps free.

The cost per unit of nitrogen in synthetic fertilizers is variable, but the cost per unit of nitrogen in organics is usually high, Lyons said. Even if the organic is free, he added, it can be costly if it needs to be shipped a signficant distance.

Synthetic fertilizers tend to be costlier due to the amount of energy required to produce them. As the cost of energy increases, so does the cost of synthetic fertilizer.

In terms of quality, Lyons said synthetic fertilizers tend to be consistent with guaranteed analysis and all the inert ingredients. Everything that’s in the bag is normally known. With organics, the consistency is dependent upon the product.

“It doesn’t matter if it comes in a bag or has a fancy label.”

In Canada, organic fertilizers must have a guaranteed analysis if they are registered as a fertilizer. Inert ingredients may change, based on the feed of the animal and based on the soil in which the plants were grown.

Environmental considerations must be looked at when choosing between a synthetic and an organic fertilizer. Less energy input is involved with organics, and if a locally-supplied waste product is being used, it is considered to be an environmentally-friendly strategy. A waste product that might otherwise be a pollutant, with a high phosporus content, might be better used in a useful environment, such as a golf course, than in an area which could prove to be potentially hazardous to the environment.

Another drawback associated with organic fertilizers is their distinct smell. 

Lyons said the benefits associated with organic fertilizers are generally environmental in nature and not agronomical.

“Make sure the product is being compared to a comparible synthetic.”

Lyons said a slow-release organic is apt to produce a better-looking turf stand after several weeks than a quick-release synthetic, noting “apples must be compared to apples and oranges to oranges.”

Common sense is necessary when weighing the benefits of organic fertilizers vs. their drawbacks, he said.

“If you’re going to go 100 per cent organic, you’re not going to get enough nitrogen. Your grass is going to be starved for nitrogen. You’re going to have to use some synthetic in a turf agronomic system.”