Lawn Lingo: Fall Lawn Care
04 Sep 2009
Fall is the time to prepare your lawn for spring.
A lawn expert explains why “green” lawns are greener and what you need to do in the fall to get your lawn ready for spring.
Have you ever wondered why some well-kept lawns are greener than others, particularly organically maintained lawns?
Organic products feed the soil, building a strong foundation that over time results in a darker, thicker and more drought-resistant lawn. Synthetic fertilizers primarily feed the grass, which results in depleted, dead soil.
Why are organic fertilizers better for lawns? Besides the obvious answer—plant-based organic fertilizers derive from renewable resources like corn-gluten meal, soy meal, yucca extract and sugar beets, while synthetic fertilizers are petroleum-based products—the best answer is that organic fertilizers release nitrogen slowly; synthetic fertilizers are fast-release. When fast-release nitrogen comes in contact with water, all the nitrogen is available for immediate uptake by the plant. Organic slow-release nitrogen means that soil microorganisms must first break down the fertilizer before the nitrogen is available to grass.
To be honest, a lawn doesn’t care if nitrogen is organic or synthetic. However, organic nitrogen is released only after soil microbes feed on the fertilizer—and it takes time for them to complete their work. Why is that important? Well, plants are old. They’ve been around millions of years, and until humans introduced supplemental fertilization, the only time plants got extra nitrogen was after it rained or snowed. Plants devote nearly all their resources to nitrogen uptake, forsaking other nutrients like iron, potassium, phosphorus, etc., until the nitrogen source is gone. Plants don’t have a shutoff switch that tells them they are full; they’ll absorb nitrogen until it kills them, which is why some lawns die of nitrogen burn.
When nitrogen is overly abundant, as in synthetic fertilizers, grass blades grow very fast, but have poor color because they don’t have a balanced diet of other nutrients like iron, magnesium, calcium, etc. Organic fertilization is like eating three balanced meals a day; synthetic fertilization is like eating one gigantic plate of spaghetti a week.
You don’t have to be a green thumb to know that plants grow better in rich soils than clay soils, but how does fertilization affect that? Rich soils have high humus content and tend to be dark in color, loose, crumbly and full of microbial activity. They’re alive because humus supports beneficial soil microbes. Microbes feed on decaying matter, like leaves and grass clippings, and then release nutrients back into the soil. The more humus in the soil, the larger the microbial population it supports, which in turn creates more humus.
Humus-rich soils retain moisture better, naturally suppress diseases, alleviate soil compaction and sustain good soil structure. Organic fertilizers contain a lot of organic matter, which is food for microbes that will eventually become humus. Synthetic fertilizers are typically petroleum-based inorganic salts, like ammonium sulfate or ammonium nitrate, which can be very damaging to microbe populations. Generally, soils that contain a lot of salt have low microbial activity, which is why synthetically fertilized lawns tend to have depleted, dead soils.
