We talked last week about getting your soil into good physical shape, and now we need to make it nutritionally healthy as well. Fertilizer is a major contributor to the health of your soil. In fact, wikipedia says that applying fertilizer is the most effective way to increase crop production and improve the quality of food. This is because even though you are technically adding nutrients to the soil, you are, in actuality, feeding your plants which absorb their nutrients through the soil. So, healthy soil= healthy plants= delicious and nutritious meals.
Fertilizer is generally made up of three main components: nitrogen, phospohorus, and potassium. When you see numbers on a bag of fertilizer separated by hyphens (such as 5-10-5) they are referencing these three components (in that specific order) and the percentage or amount of that nutrient that is in the bag. Other components of fertilizers generally include calcium, sulfur, and magnesium as well as other trace minerals.
Here is a great article to read on understanding fertilizers better: How To Make Sense of a Fertilizer Label.
Before you start fertilizing your garden, it is a good idea to have your soil tested (especially if you are using soil that was not brought in, but is straight from your ground). Different plants do better with different nutrients and if you add the wrong kinds of nutrients, or too much of something already in the soil, you could be throwing away money, or worse, killing your crops. You get your soil tested at your local county extension (most will allow you to mail in a sample) and it generally costs a fee, but again, it could save you money and wasted effort in the long run.
The way you fertilize will depend upon the type of soil you have. According to the Texas Home Vegetable Gardening Guide, if you have heavy clay soils you can fertilize quite heavily at planting time and the soil will safely absorb and store the fertilizer. However, if you have thin sandy soil (soil which generally needs the most nutrients), you can only apply light amounts at a time or else you risk burning your plants. So you would want to fertilize more regularly but in light doses. (Contact your county extension for recommendations on how often based upon your specific soil.) Also note that if you purchased soil for your garden from the store, it may have already come with fertilizer in it. Check the soil bags for information so you don’t over-fertilize.
Generally you add fertilizers after your seeds have sprouted and are a little more sturdy (about 3 weeks in or so). However, before you plant your garden, you can apply a preplant fertilizer (such as a 5-10-10 for sandy soil, or a 10-20-10 for clay) at the rate of about 1-2 pounds per 100 square feet of garden a few days in advance. Mix the fertilizer into the soil well to distribute the nutrients. After a few days, go ahead and plant! Woohoo! You’re on your way to an amazing garden!! 😀
For some other great articles on understanding fertilizers better, try these: