If your garden soil is naturally rich in organic matter, an inch or so of compost at the beginning of the season and again in midsummer is probably plenty. If you have very sandy or nutrient-depleted soil, provide as much compost as possible – several inches at the beginning of the season, a few handfuls for each plant at transplanting time, and a thick re-application in midsummer. If you have very poor soil it is also a good idea to rotate the growing area and grow nitrogen-fixing cover crops to increase the organic matter and nutrient content of the soil. The best way to determine your nutrient needs is to do a soil test. Soil can be tested using a simple test from the garden garden center, but a professional soil test will provide more detailed information and recommendations for amendments. Soil samples can be sent to UVM Extension for soil testing for about $14. Find out more about soil testing here.