Using Leaf Compost

Using Leaf Compost

Composting involves primarily the microbial decomposition of organic matter. Compost - the end product - is a dark, friable, partially decomposed substance similar to natural organic matter found in the soil. The organic matter content of soils is very important. It influences the physical condition, water-holding capacity, and temperature of the soil, andespecially the soil bacterial processes which affect theavailability of mineral salts to plants.

Why Compost Leaves

If newly fallen leaves are added directly to the soilwithout first being composted, the microbes thatdecompose the leaves compete with growing plants for

soil nitrogen. The temporary nitrogen shortage causedby the microbes can reduce plant growth. To reduce oreliminate this competition for nitrogen, composting of the leaves is recommended prior to incorporating theminto soils.

Need for Organic Matter

Most New Jersey soils need an increase of 1/2 to1% in organic matter. Sandy soils, such as loamysands and sands, and soils with very high clay contentare improved the most by an increase in organic matter content.

Benefits of Adding Leaf Compost to Soil

Among the benefits derived from adding leaf compost to New Jersey soils are:

Drought damage to plants is reduced becauseof an increased water-holding capacity of thesoils.Soil tilth is improved making the soils easierto cultivate.

When Compost is Ready to Use

When compost is ready to use (6 to l8 months afterstarting) its temperature will generally have decreasedto slightly above air temperature. Finished compostwill usually be drier than leaves during composting.The material also will be crumbly in texture. Beforeusing compost, “screening” may be necessary toremove the larger partially decomposed materials.

These materials will sometimes be present incomposting piles because not all items decompose atthe same rate. The undecomposed organic matter clumps may be broken up and added to another activecompost pile for additional decomposition. Adding Leaf Compost to the Soil A good rate of organic matter to work into the top 6 1/2 to 7 inches of most New Jersey cultivated soils is0.5 to 1.0% organic matter by weight. This is equiva-lent to adding 900 to 1,800 wet pounds (25 to 50bushels) of leaf compost per 1,000 square feet of area.To accomplish this, spread a 3/8- to 3/4-inch depth ofleaf compost uniformly over the soil surface and mixinto the top 6 to 8 inches of soil.Little or no nitrogen will be released from compostfor plant use during the season immediately following incorporation into the soil. It is generally necessary toadd nitrogen to soils containing compost to prevent thecompost from “robbing” the soil of nitrogen and creating deficiency problems in plants grown in thesoil. Adding 1 to 1 1/2 lbs. of 10% nitrogen fertilizerto each 100 lbs. (about 3 bushels) of leaf compost isrecommended.

The preceding recommendations supply only theneeds of the leaf compost. Most plants require anadditional 1 to 3 lbs. of actual nitrogen per 1,000square feet for normal feeding. This nitrogen should beapplied to the soil in addition to that applied in the leafcompost.

Using Leaf Compost as a MulchLeaf compost can also be used as an organic mulchon the surface of soil in place of peatmoss, straw, etc.Organic mulches are valuable because they:Reduce rainfall runoff, thereby making morewater available for plant growth.Very small amounts of the 16 essentialelements needed for plant growth are supplied.Adverse effects of excessive alkalinity,acidity, or over - fertilization are reduced by theadded buffering of the soil.The cation exchange capacity of soils isincreased, enabling the soils to hold moreplant nutrients for longer periods.

Decomposition of the organic matter producesorganic acids which combine with iron andaluminum ions, thereby reducing theirpotential toxicity to plants. This also makesmore phosphorus available for plants becausefree iron and aluminum can tie up the phos-phates. The added organic matter provides a food source for desirable soil micro-organisms. When incorporated into the soil, or used in athin mulch 1/16- to 1/8-inch thick, composthelps seeds to germinate.Overall, compost improves the physical, chemical,and biological properties of soils. Leaf compost,however, is not normally considered a fertilizer as it istoo low in nutrient content. It serves primarily as anorganic amendment and a soil conditioner. Thenitrogen content of composted leaves on a dry basis isabout 1/2 to 1% by weight. For other materials commonly added to backyard leaf compost piles, thenitrogen content is:

blood meal 10-14%; 

grass clippings2-4%; 

coffee grounds 1 1/2-2%; 

eggshells 1-2%; 

horsemanure 1-5%; 

cow manure 1-1 1/2%; 

poultry manure3-5%; 

ammonium sulfate 20 1/2%; 

urea 45%; 

bonemeal 1 1/2-4% and 

cotton seed meal 6-7%.

Decrease water evaporation losses from thesoil.Keep the soils cooler in hot weather andwarmer in cold weather. Reduce alternate freezing and thawing of soils which can injure the fibrous roots of plants. Help to prevent soil erosion by wind or water. Keep soils friable, therefore easier to cultivate.Increase biological activity of earthworms andother soil organisms.

Prevent soil spattering on leaves, flowers, orfruits such as strawberries.Reduce soil compaction from rain andirrigation water.

Help to control weeds.Present a pleasing appearance.Recommended thicknesses of mulch layers: 2-3inches for deciduous shrubs and trees, vegetables, and rosebeds; 3 inches for flower beds; and 3-4 inches forshallow-rooted, acid-loving plants.Other Uses for Leaf CompostLeaf compost may also be used in potting soil.

However, no more than 25 to 30% of the potting soilshould be leaf compost. Frequently leaf compost willcontinue to decompose. If more that 25 to 30% of the

potting soil is leaf compost, there will be a significantvolume reduction of the potting soil after 1 year.Composting generally destroys most weed seedscontained in the compost material; however, not all of

them will be destroyed. Some are heat resistant, andothers will not be fully exposed to the high temperatures. If a completely pasteurized leaf compost isdesired for potting soil, it will be necessary to heat it inan oven until the temperature of the center of the massreaches 180oF and is maintained for 30 minutes.. 🙏