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Fertilizers

Fertilizer   is an incredibly complicated topic. Soil fertility is not as easy as "things grow" or "things don't grow." Just like people, plants need a wide and balanced variety of nutrients. After all, fats, carbohydrates and protein may be the three "basic" nutrients for humans, but a human raised on just these three things wouldn't be as healthy as a human with a varied diet. Humans need "micronutrients" like vitamins   and minerals, and plants need many of the same things!

While plants make their own basic food by photosynthesis, they still need a number of other nutrients for growth, flowering, fruiting and other life cycle functions. They get carbon and oxygen from the atmosphere but for most other elements they depend on the soil and, by extension, on you.

Furthermore, the soil environment can affect plants in other ways besides the supply of nutrients. Some plants may prefer a more acidic or basic soil, but most prefer a neutral or very slightly acidic pH. If your soil pH is too high or too low, you should add the appropriate material to balance it out. Soil pH can be determined with an easy-to-use soil testing kit .  Soil pH mainly affects how well your plants can absorb nutrients from the soil and which nutrients are available, so it is important to maintain the right balance.

Plant Nutrition

Just like people, plants need different nutrients in different amounts. Some are readily available from the environment -- air and water provide carbon, oxygen and hydrogen. Everything else comes from the soil and, by extension, from you. This is especially true of houseplants   and container gardens ,  which have only a limited amount of soil   to work with, but all of the plants in your garden from crocus to oak tree need many of the same nutrients.

Natural (Organic) Fertilizers

There are many kinds of natural fertilizers,   These can be divided into three main categories: animal, vegetable and mineral. In this context, "organic" refers to "from natural sources/approved for organic farming and gardening." Note that "organic" fertilizers can be entirely composed of inorganic materials.

Animal Byproducts

Most animal product fertilizers are by-products from the meat, egg and dairy industries. If you are adamant about having an organic and vegan garden, skip this section and read up on plant-based fertilizers. Keep in mind, however, that these fertilizers are made from parts of the animal that would otherwise be wasted anyway, so animal-based fertilizer doesn't necessarily contribute further to the meat industry.

Plant-Based Fertilizers

Mineral Fertilizers

Synthetic Fertilizers and Plant Food

In the last 100 years, our knowledge of chemistry has given us the power to create precise blends of chemicals in labs. Like any technological leap, synthetic fertilizer has taught us that Spiderman   knows best -- with great power comes great responsibility. Synthetic fertilizers can give great results in your garden but they can also be dangerous to your plants, your family, your pets and the environment when not used according to label usage and safetly instructions. Use caution when using any synthetic fertilizer and take appropriate precautions to protect yourself during applications. Use the absolute minimum for your garden; fertilizer runoff is a major pollutant in the ocean, where it can trigger algal blooms that suffocate other ocean life.

Synthetic fertilizers have another downside -- the rising costs of oil. The connection may not be immediately obvious, but it does exist. Nitrogen is not an easy element to "fix" -- that is, to render usable by plants. It takes a lot of energy to fix nitrogen, and most of that energy comes from oil. As energy prices continue to rise, fertilizer prices will rise as well. Composting ,  however, requires very little energy input from humans; the bacteria and other microorganisms do most of the work. Read up on composters   and backyard composting before buying fertilizer, and save yourself a lot of money in the long run.

Fertilizer

There are two kinds of fertilizer: liquid   and granular. Granular fertilizers   can be further divided into slow-release   and quick-release . 

Liquid Fertilizer   Granular Fertilizer  
  • Absorbed quickly and fast-acting.
  • Also washes away quickly; requires reapplication every 2 to 3 weeks.
  • Sold as concentrates; need to be diluted before use.
  • Some brands require specialized attachments that hook up to your hose for easy mixing while watering.
  • Applied dry, needs to be watered to start working.
  • You can see how much is being applied.
  • Applied by hand or with a mechanical spreader.
  • Slow-Release   (aka water-insoluble nitrogen (WIN))
    • Has a coating to slow release of nutrients.
      • Sulfur-coated lasts about eight weeks.
      • Polymer-coated lasts about 12 weeks.
  • Quick-Release   (aka water-soluble nitrogen (WSN))
    • Last three to four weeks.

Plant Food

Plant foods   are a type of fertilizer that is usually formed into a small, slow-release tablet   or spike   and is formulated for a specific kind of plant, such as African violets .  They're usually used for houseplants, but some are available for outdoor plants such as roses   or rhododendrons .  These are usually spikes that are inserted into the soil near the roots of the plant. There are a number of blends available; formulas for foliage plants contain lots of nitrogen, while food for flowering plants is heavier in phosphorus.

Plant foods are a good choice for potted plants .  Since potted plants need frequent watering, nutrients are rapidly washed out of the soil. A slow-release food spike   can help mitigate this loss.

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