Nitrogen is an important component of healthy garden soil. It is an ingredient in all fertilizers, most commonly seen with just the elemental designation that is assigned to it as part of the Periodic Table, N. In commercial fertilizer preparations that bear a number sequence on the packaging (i.e. 12-6-6), nitrogen is represented by the first number. The other numbers represent phosphorus and potassium, respectively.
Nitrogen is most beneficial to the growth of leaves and stems on the plant, and as a result you will notice that almost all grass and lawn fertilizers are very high in nitrogen. In fact, they are most often too high in nitrogen, producing green lawns that look good on the surface but lack a strong and resilient root system that can help them weather drought conditions. These lawns will brown easily.
Likewise with garden plants, too much nitrogen is not a good thing. Just as with the lawn, nitrogen overload in the garden will result in underdeveloped roots that cannot adequately support the extra leaf and stem growth.
On the other side of the coin, when do you know that you need more nitrogen in the garden?
The most common indication of a nitrogen deficiency in the garden is when the leaves on your plants – especially the older growth – begin to yellow prematurely. Growth is also often stunted in plants affected by a lack of nitrogen as well.
Sources of Nitrogen
Bar none, my favorite natural source of nitrogen for the garden is composted chicken manure. It is sold in many independent garden centers in a pelletized form that is easy to apply (not to mention far less messy). Other composted manures are also good sources of nitrogen, but chicken manure is available in smaller quantities, whereas other manures usually require a larger size purchase that may not be practical for urban gardeners. Don’t ever apply fresh (uncomposted) manure to an actively growing garden!