Could uncomposted fallen tree leaves from the fall be used as an inexpensive soil amendment to increase aeration and improve soil structure?
Hi, Most leaves need a year or more likely two to break down sufficiently to be used as an amendment. We have Oak leaves here where I live and it takes two years for them to be decomposed enough to add to the soil. (the tannin acids need to leach out along with generally physically breaking down)
When un-decomposed leaves are added to the soil they take nitrogen away in the decomp process. When preparing your leaves for use as an amendment You can compensate AND speed up decomp by adding hi nitrogen fertilizers (lawn ferts) to the pile and or 'Rid-ex' (septic tank enzymes). Both will speed decomp. I also wet & cover my leaf piles with black plastic to heat the pile up. (be sure to stir the piles now and then to avoid spontaneous combustion when using hi nitro ferts and Rid-ex, things can really get cooking on a hot day!)
Another reason not to use Un-decomposed leaves is that they can form sort of a barrier to water and nutrients if they matte down into thick layers in the dirt anywhere.
I like to 'till' my leaves with a small mini tiller. It grinds them up and also speeds the break down. You can also run a lawn mower over them repeatedly for the same effect.
So yes you can use the leaves they just need time to decompose enough depending on what kind they are.
If you really want to add something to the soil to help aerate it and add structure add 3/16th's red or black volcanic cinder (available at most landscape rock yards), it acts like a super durable 'perlite', holding water nutreients AND most importantly, AIR in it's volcanic pockets. Good Luck! Happy Gardening! GrowIT!
