When Do Soil Organisms Do Their Work?
The activity of organisms is constantly changing with temperature, moisture, pH, food supply, and other environmental conditions. Different species prefer different conditions, so even at maximum total activity levels only a minority of soil microbes are busily eating and respiring. The highest total activity is in late spring/early summer and in late summer/early fall when the soil is warm and moist. In early spring, some farmers see nutrient deficiency symptoms in their plants because not enough microbes are warm enough to convert organic compounds into plant-available nutrients. Leaching of excess nitrate often happens in early spring when the soil is too cool for either plants or microbes to grow and immobilize the nitrogen.
As stated above, microbial activity varies throughout the year. Different species become more or less active depending upon the environment they favor. Most favor warm temps, fewer favor cold temps. Some favor more water, some less. Some favor eating grass clippings while others favor tree leaves. Some microbial species favor oak leaves over maple & vice versa. And on and on....
As for nitrogen, some species of microbes will make it plant available and others will sequester it. One recent study shows that microbial activity in the fall will sequester N and release it in spring, making it plant available when plants are coming out of dormancy.
Another recent study shows that applications of N reduce microbial biomass and activity. Think this one through, are we hindering a natural process which favors plant health when we add additional N?
Applying compost in the spring will most likely release nutrients and enzymes
in time to reduce summer stress, but not in time to influence spring green up.
Basically, it is in favor of the health of plants to encourage a wide diversity of soil microbiology for plants to prosper.