Sustainable Planet Today

When it comes to fertilizing your home vegetable garden, organic products have many benefits. But, they can also be expensive and a little confusing when you are trying to determine how much to use in your garden.

To fully understand the fertilization issue we must first understand how the plant uses nutrients. In this example, I’ll focus only on nitrogen.

Nitrogen is the central element in chlorophyll, the material in plants that performs photosynthesis and produces the green color in the leaves. Nitrogen is very mobile in the soil in the inorganic form. Thus, it is moved through the soil profile by rainfall and irrigation. This nitrogen eventually becomes unavailable for the plant’s root system.

To a great extent, nitrogen is also responsible for vegetative growth. A lack of nitrogen will produce little in the way of leaves and stems. Too much and the plant will go into a solely vegetative mode and will not produce any flowers or fruit until a balance is reached.

The typical organic fertilizer will have a low percentage of total nitrogen in the analysis equation. The analysis equation for fertilizers of any kind is usually represented in the form of N-P-K, which stands for Nitrogen, Phosphorus, and Potassium. Other micro-nutrients, if present, are listed separately in the analysis profile.

In the case of bagged compost, an example analysis might be 2-4-1. In simple terms these numbers are given as percentages. In other words, 2% nitrogen would mean a 100 pound bag contains 2 pounds of total nitrogen.

Reports from university trials specify that 40 to 100 pounds of total nitrogen per acre is needed for most vegetables to produce optimal growth over a season. This number varies depending on soil types and locations throughout the United States. I typically target 100 pounds for each growing season. Going back to our example above, doing the math reveals that we would need 40 to 75 bags (or 4000 to 7500 pounds) of compost per acre.

Most of us are not growing our vegetables in acre sized gardens. I like to convert this down to 100 foot rows. If we assume the rows in the per acre example are 100 feet long and are spaced 4 feet apart, we have approximately 109 rows per acre (there are 43,560 square feet in an acre). And, if we use 100 pounds of total nitrogen per acre as our target, we need about 0.92 pounds of total nitrogen per 100 foot row. For ease of calculations, let’s round it up to 1 pound.

Going back to the bag of compost with an analysis of 2-4-1, we would need 50 pounds per 100 foot row or a half a bag.

An advantage of organic fertilizers such as compost is that the total nitrogen is not immediately readily available. This allows us as gardeners to be able to apply the total amount at the beginning of the season knowing that it will become available as the season progresses. In addition, organic fertilizers give us the added benefit of building up the total organic matter content of our soils.

Using organic fertilizers in the home garden is a great way to continue to help the environment while providing healthy food for your family.