This is Part One of a four part series titled, Understanding Soil Nutrients. Each day this week will bring a new article on soil nutrients, with Thursday being the final article.

The first part of the Understanding Soil Nutrients series will be on nitrogen. As vegetable gardeners, nitrogen can play a key factor in whether our vegetables grow successfully or are doomed for failure. Too much nitrogen can mean big, bushy plants that have brilliant foliage, but little or no fruit. Not enough nitrogen causes browning foliage, and plants with stunted growth.

In most cases there is a fine line between too much and not enough nitrogen levels. Having your soil analyzed by a soil test is very important in determining how much nitrogen content is in your soil. The test results will inform you whether you need to add nitrogen, or dilute nitrogen levels depending out what you intend to grow.

So let's quickly study some important factors dealing with nitrogen.

Why Is Nitrogen Important For My Vegetable Garden Soil?

Nitrogen is a key element found in soil, but is mostly comprised in our atmosphere ( air is 78% nitrogen). Although nitrogen is abundant, plants can not use it until it is processed in the soil, or added by fertilizers. Nitrogen is commonly referred to by its elemental abbreviation (N), in fertilizers. Fertilizers are denoted for their Nitrogen (N), Phosphorus (P), and Potassium (K), or simply N-P-K, content - usually as a percentage of how much of each nutrient the fertilizer contains.

All fertilizers will have the N-P-K analysis labeled on the bottle. If you look at the picture below, you will notice the numbers 2-1-1 on the label. This means this fertilizer contains 2% Nitrogen, 1% Phosphorus, and 1% Potassium. Nitrogen is always the first number, and usually (but not always) the highest.

Fertilizer Nutrient Content

Nitrogen is responsible for the leafy green foliage in plants as well as protein and chlorophyll development. Chlorophyll is what gives the foliage its green color and is vital for photosynthesis. Tiny soil microbes make nitrogen available to plants by breaking down organic matter and steadily releasing two inorganic forms of nitrogen-ammonium and nitrate.

Seasonal fluctuations of ammonium and nitrate levels are normal, because the soil microbes that break down organic matter are less active in cool soil. Also, soil has the capacity to retain ammonium until the plants need it, but soil can't hold on to nitrate.

This means that your plants must either use nitrate or lose it, because at the end of the season, leftover nitrate moves out of the soil by leaching, through runoff, and by converting into gaseous atmospheric nitrogen. Nitrate that finds its way into watersheds causes serious, negative impacts on water quality. This is another reason to watch how much nitrogen you add to your garden. Adding too much can end up in water supplies, killing sea life and damaging the quality of the water.

Adding Nitrogen To Vegetable Garden Soil

You can prevent excess nitrate from entering the environment by following recommended application rates:
  • For compost - add a 1- to 2-inch layer of compost to the garden soil. This should give the soil adequate nitrogen.
  • composted manures - add 100 pounds per 1,000 square feet of your vegetable garden area.
  • fertilizers - if using commercial fertilizers, always use the recommended amounts according to the manufacturer's label.

You can apply excessive amounts of nitrogen with manures and compost as well, so take caution with organic materials as well. An excess of nitrogen, caused by fertilizer over application, can result in rapid, lush growth and a diminished root system. In extreme cases too much quick release nitrogen can cause burning of the leaf tissue, and plant death.

Check back tomorrow for part two of Understanding Soil Nutrients - Phosphorus (P). Make sure you don't miss any of the Understanding Soil Nutrients Series by subscribing to our RSS Feed, or by bookmarking us!