In visiting the Howard County community gardens with the "Ask A Master Vegetable Gardener" program, I've seen many beautiful vegetable gardens and more than a few poor performing gardens. Invariably, the poor performers belong to first or second year gardeners, who don't have a good grasp of the soil and nutrient requirements for a good garden.
In talking to these novice gardeners, I ask them if the have ever tested their garden's soil to determine its pH and nutrient levels. When they answer "No", I open my backpack and give them a soil test bag and HGIC Pub 101. I tell these novice gardeners how important it is to have the proper soil pH and adequate levels of nitrogen, phosphorous, potassium and other macro and micro nutrients in the soil so that plants can make good growth.
Most of these new gardeners want to grow their vegetables organically and they have amended their garden with compost and other organic material. In a lot of cases, incompletely composted organic material has been added and that product is actually taking nitrogen out of the soil. For these gardeners, I give them the nitrogen recommendation for gardens low in organic material found in HGIC Pub 42 . The recommendation is to add from .1 to .2 pounds of nitrogen per 100 square feet. I usually suggest soybean meal be use which has an N-P-K of 7-2-1. To determine how many pounds of soybean meal are required to put down .1 pound of N, I explain you just divide the .1 pounds of N by .07 ( the percent of N in a pound of soybean meal) to come up with approximately 1.4 pounds of soybean meal per 100 square feet. To put down .2 pounds of N you simply double the application rate or apply 2.8 pounds of soybean meal. This calculation works for all fertilizers, so just divide your desired amount of N by the percentage of N from the label on the bag.
So, if your garden isn't performing up to your expectations, do a soil test and in the interim add some nitrogen per the HGIC recommendation for soil with low levels of organic material, if you didn't add any at planting time.