The advantages for removing leaves is that the lawn looks clean and aesthetically pleasing; and in the case of sports like golf removing leaves makes finding your golf ball much easier. Additionally, removing leaves reduces the shading to the turf and the possibility of moist conditions developing that may enhance fall and winter disease development.
The advantages of returning or mulching leaves back into the lawn or turf include 1) reducing the cost of bagging, raking, and disposing of leaves, 2) nutrients primarily nitrogen are recycled; and 3) potential benefits. Regarding nutrients specifically nitrogen being released and returned for turf growth depends on the carbon:nitrogen (C:N) ratio. Soil microorganisms use carbon for energy and nitrogen for maintenance and growth. Within the microbes a C:N ratio of 8:1 is ideal for living. To acquire the necessary carbon and nitrogen in the soil to maintain an internal 8:1 ratio the microorganisms are ideally at a C:N ratio of 24:1.
In contrast, if we were to add grass clippings with a C:N ratio of 19:1 the soil microorganisms would consume the leaves and releasing extra nitrogen (mineralization) resulting in a temporary soil nitrogen surplus. With grass clippings having a C:N ratio close to 24:1, the amount of excess nitrogen immediately released might be minimal (although the nitrogen would eventually be released). However, because of the C:N ratio, grass clippings are readily broken down in a short period of time.
In general, if the C:N ratio > 30:1, immobilization of nitrogen occurs as maximum biological activity is reached. With C:N ratio < 20:1, mineralization of nitrogen is reached with maximum biological activity.
A few examples of C:N ratios of organic matter.
|Leaves, variety of||35:1 - 85:1|
|Tree bark||200:1 - 491:1|
|Sawdust (weathered 2 months)||625:1|