Fertilizer Facts


The ratio 12-8-10 might sound like the ideal body measurements for today's boyish Hollywood actresses, but it's actually a series of percentages explained by the mysterious acronym NPK.



Plants and grasses need nutrients in order to grow. Some of those nutrients, such as carbon, hydrogen, and oxygen, are obtained freely from air and water. But other nutrients aren't always abundant in nature. Organic fertilizer and synthetic fertilizer are concentrated sources of the chemicals plants require for life, particularly the macronutrients nitrogen, phosphorus, and potassium.


Buy the numbers


Plants require both macronutrients and micronutrients, but fertilizer typically contains mostly macronutrients. Micronutrients such as calcium, magnesium, boron, iron, copper, and zinc are needed in much smaller amounts, and are less important for plant growth than macronutrients.


The macronutrients nitrogen, phosphorus, and potassium give plants the energy they need to flourish. Fertilizer that contains those three elements is sometimes referred to as NPK fertilizer, after the symbol for each chemical on the table of elements (phosphorus got the P, so potassium is known by K). How much of each chemical your plants or lawn require should determine the concentration of NPK fertilizer you buy. This need can be measured through a soil test.


Bags of fertilizer display numbers correlating to the percentage of N, P, and K inside. For example, if you need fertilizer that is higher in nitrogen but lower in phosphorus, you might select a 12-8-10 fertilizer, which is a fertilizer with 12% nitrogen, 8% phosphorus, and 10% potassium. The other 70% is mostly ballast or waste, often limestone.


Special purpose fertilizers have a greater percentage of one chemical than another, such as phosphorous for flower gardens. Fertilizer can also be slow release or fast release. These terms refer to the speed with which nitrogen is released from the fertilizer into the soil.


Organic fertilizer


The term organic fertilizer refers to fertilizers that appear organically in nature, such as manure, peat, or slurry. Organic fertilizer can also be manufactured, as in the case of compost or bone meal.


Organic fertilizer is preferred by some gardeners over synthetic chemical fertilizer because it is natural and releases nutrients at a slower rate. Synthetic fertilizer has a higher density of nutrients than organic fertilizer, but this can sometimes cause plants to burn, a term used for when plants are dehydrated by excessive fertilizer salt.


Lawn fertilizer


Lawn fertilizer tends to contain more nitrogen than general-purpose fertilizer (a standard NPK ratio for lawn fertilizer is 3:1:2 or 4:1:2). The primary decision with regard to nitrogen in lawn fertilizer is slow release or fast release.


Fast-release lawn fertilizer is usually cheaper than slow release, and will likely provide a quick burst of greenery. On the downside, fast-release lawn fertilizer can promote excessive topgrowth, and is more likely to burn the grass. Slow-release lawn fertilizer will cost more and take longer to work, but is the better choice for a uniform, healthy lawn.


Form is also a consideration when buying lawn fertilizer. Some people prefer liquid lawn fertilizer to dry fertilizer, but there's no significant advantage conferred by buying one over the other. Liquid lawn fertilizer can be easier to measure or handle, but dry lawn fertilizer is considered by some to be longer lasting and more reliable.


If you're a do-it-yourselfer or just don't like the idea of adding synthetic fertilizer to your lawn, homemade lawn fertilizer is another option. Homemade lawn fertilizer is also a lot cheaper than buying organic fertilizer.


Homemade lawn fertilizer recipes might appear ridiculous, but they're proven to work. In case you're wondering, ammonia provides nitrates, soap improves spread, and beer encourages microbial activity:


1 cup of beer (regular, not light)
1 cup of ammonia or fabric softener
1 cup of baby shampoo
1 cup of liquid lawn food
1/2 cup of molasses or corn syrup


--Joshua Avram

Back to Copywriting page