Autumn Leaves have been known to be beneficial to garden soil, either as a mulch or compost (link to our easy how to compost article) component. But what nutrients contained in them? Well, I’ll give you the straight facts from numerous studies on what nutrients are in leaves!
Fall Leaves are a significant source of nutrients such as Carbon, Nitrogen, Phosphorous, and Potassium. As leaves decompose via microbes or worms, these essential nutrients are released into the soil. Leaves also contain various amounts of 12 other nutrients and minerals that likewise feed and improve your garden soil’s fertility.
Nutrient Concentration in Leaves
Rutgers University did a study a number of years ago analyzing the nutrient content of leaves. They gathered leaves from various municipalities across New Jersey, and measured the nutrient concentration.
|Nutrient||Average Concentration (%)||Range (%)|
Additional trace nutrients and minerals were identified and measured as follows:
|Nutrient||Average parts per million||Range (ppm)|
So, although the concentrations are small, leaves can still be a valuable component to promoting soil health and fertility. In addition to feeding worms, a leaf mulch (link to our article reasons to use leaf mulch) on will slowly decompose, depositing the above nutrients overtime.
It has been shown that the amounts of nutrients vary substantially based on the species, starting soil fertility, and climate. 
How do the nutrients become available to plants?
The leaves will be decomposed via microbes and worms. Worms will readily consume leaf litter and secrete it as worm castings, improving soil fertility.
Additionally, leaves can act as a ‘brown’ compost material. So, any leaves that are not applied to the garden directly can be added to a compost pile or compost bin.
Link to our post on our easy way to compost==>Learn how to start composting
Also, you can make your own ‘Leaf Mold’ by bagging or piling up leaves alone. Keep moisture and air available, and in 12 months to 3 years you will have leaf mold.
How long does it take for the leaves to break down?
Leaves used in compost can be broken down in as little as one month with frequent turning and enough nitrogen. Typically though it will take at least several months as leaves become available as the weather gets colder. Cooler temperatures will slow decomposition in compost piles.
Leaves used as mulch will be generally be broken down by the start of Summer, 23 June. So, it will take up to six months for worms to breakdown leaves.
Should you till leaves into your soil?
Tilling leaves into the garden soil will be a fast way to add organic matter, which can break up compacted clay. But, this will create a nitrogen sink. A nitrogen sink is where the leaves will consume nitrogen from your soil rather than adding nitrogen. A better solution is to make a leaf mulch
(Related – read our top reasons to use leaf mulch!)
A leaf mulch will decompose in two ways. First, microbes and other bacteria will feed on the leaves, which promotes soil health. Second, worms eat the leaves and transfer them as worm castings as they move throughout the soil. So, you get the reduced compaction without consuming additional nitrogen!
PIN IN FOR LATER:
 Plant Nutrients in Municipal Leaves. Joseph R. Heckman, Ph.D., Extension Specialist in Soil Fertility; Daniel Kluchinski, Mercer County Agricultural Agent; and Donn A. Derr, Ph.D.. Rutgers Cooperative Research and Extension.
 The influence of earthworms on soil fertility. II. Consumption of soil and organic matter by the earthworm Allolobophora caliginosa (Savigny). KP Barley. Australian Journal of Agricultural Research 10(2) 179 – 185
 – A global study of relationships between leaf traits, climate and soil measures of nutrient fertility. Jenny C. Ordoñez et all. Global Ecology and Biogeography, Volume 18, Issue 2. 2009
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