Nitrogen Sources

Soil tests in Central Texas reveal a lack of nitrogen.  If the leaf is pale yellow, and the plant shows a lack of vigor, it can be a sign of nitrogen deficiency.  (If the veins are darker against pale leaf, the plant has an iron deficiency). 

Before waiting for your plants to show signs of nitrogen deficiency, one thing is to get a soil test. 

Where to get a soil test:
Texas Plant & Soil Lab
Your Extension Office

Nitrogen and other nutrients aren't always available to the plants, even though they may exist in the soil.  They have to go through a process where the microorganisms can convert them in to an available form. Compost is one way to do this since it is an energy source for the microorganisms.

Nitrogen amendments:

Fish emulsion:  2-3% nitrogen
Quickly available to plants, can be used as a foliar feed. 

Earthworm castings: 1% nitrogen
Add to the growing medium for a great start to seedlings.

Coffee grounds:  2% nitrogen
Good way to amend the soil since it opens it up and fluffs it up nicely. 

Turkey compost:  2% nitrogen

Alfalfa:  3% nitrogen  (3-1-2 formula)
Rosarians love this one. It contains tricontanol, a powerful plant growth regulator.

Cottonseed meal: 7%  (7-2-1 formula)
Also helps acidify soil over time.

Granular organic fertilizers (8-2-4)
Good way to feed the lawn as well as ornamentals.

Feather meal:  12-0-0.

Grass clippings: natural way to add nitrogen when you mow the lawn.