| Soil, Fertilizer, Mulch & Compost - May 2008
Please Note: All recommendations are for central Maryland. Time frames shift two weeks earlier in Southern Maryland and the Eastern Shore and two weeks later for Western Maryland. Check publications for further information.
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Soil
Have your soil tested and be prepared to raise or lower soil pH according to the written recommendations you receive.
Earthworms are a sign of healthy soil. Contrary to popular belief, heavy rains don't drown earthworms (they have no lungs) or drive them out of the ground. They come to the surface during wet periods to mate more freely. They die because they dry out or are parasitized by insects and diseases. Soil insecticides will also drive them out of the soil. Poor, compacted soils can be improved through the generous addition of organic matter. Spade or till in a 6-8 inch layer of leaf compost or well-rotted manure.
Bare soil is prone to erosion and should be covered with mulch, groundcovers or turf. Avoid the temptation to turn over or dig into wet soil. This can cause long-term damage to the structure of your soil. How do you know when your soil can be turned or tilled? One test is to form a clump of your soil into a ball. If it breaks apart easily it’s probably OK to work. Tilling wet soil can cause it to become cloddy and brick hard when it dries out. If you want to grow vegetables, flowers, or herbs and your soil is especially poor, consider building a raised bed and filling it with a purchased mixture of topsoil and leaf compost.
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Fertilizing Plants
Newly set flower and vegetable transplants can have a difficult time getting established because the soil is still cool. Plants may turn pale and “just sit there”. Remedy this problem by applying a balanced soluble fertilizer directly to the root zone or foliage.
Fertilize plants according to their specific needs based on soil test recommendations. Trees are typically fertilized after they drop their leaves in the fall, not in the spring. Mature shade trees do not typically need to be fertilized at all. Trees get more than enough fertilizer when turf is fertilized in the fall.
Bluegrass and fescue turf are fertilized in the fall as well. Spring fertilization of lawns is not necessary unless you failed to fertilize in the fall or your turf is weak, thin and pale. When selecting a lawn fertilizer choose those containing a minimum of 40% water insoluble nitrogen.
To prevent nutrient pollution of groundwater and the Chesapeake Bay keep fertilizers off of hard surfaces like driveways and sidewalks. Be cautious when fertilizing areas of your yard that border these hard surfaces.
Avoid the temptation to fertilize ornamental garden plants that appear to be healthy and productive. Over-fertilization with fertilizers, especially those high in nitrogen, can lead to overly succulent, weak growth and encourage sucking insect pests like scales, aphids and adelgids.
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Compost
Compost contains major and minor nutrients important for plant growth and can be used in flower, herb and vegetable beds to substitute for commercial fertilizers.
This is a good time to turn compost piles, remove woody materials and add a nitrogen source to accelerate the breakdown process.
Compost piles should be at least one cubic yard in volume to heat up properly. An even mixture of green (high nitrogen) and brown (high carbon) materials is necessary for rapid composting. Grass clippings and spent plants from the flower and vegetable garden provide a good source of “green” materials for the compost pile. Fallen leaves and old straw mulch are good sources of “brown” materials. You can hasten the composting process by shredding materials, turning the pile, maintaining an even mixture of high nitrogen and high carbon materials, and by keeping the pile moist. If your pile is overly wet and smelly, mix in some dry materials high in carbon, like shredded newspaper, straw or shredded leaves.
Keep sticks, roots and woody stems out of your compost pile. They take too long to breakdown and make it difficult to turn the ingredients.
It is not necessary to buy a bioactivator to add to the compost pile. Finished compost is the very best starter material for a compost pile because it contains nitrogen and a huge number of microbes. It is also not necessary to add soil or lime to a compost pile. Consider placing a tarp or lid over your pile to prevent water logging during wet periods, conserve moisture during dry periods, and prevent nutrient leaching. Animal based kitchen scraps thrown on top of compost piles may attract pest animals. It is best to bury these scraps in the middle of your compost pile or in garden soil.
Contrary to popular belief, it is not at all helpful to layer different ingredients when building a pile. Mixing together materials of different textures will promote faster decay. Many kinds of invertebrates live in a compost pile including manure worms, centipedes, millipedes, pill bugs, and pseudoscorpions. They are part of the composting ecosystem and should be appreciated, not feared.
Mulch
Select pine bark mulches for use around your home to minimize the possibility of attracting termites. Avoid any hardwood mulches that contain wood. Hardwood bark mulches are a problem around azaleas, rhododendrons and mountain laurel because they may leach toxic amounts of manganese, when soil pH is low.
Mulches should be applied only 2-3 inches deep around ornamental plants and kept away from shrub and tree trunks. Mature trees do not benefit from being mulched.
Very large mulch piles may undergo anaerobic digestion leading to the formation of compounds like ethanol and methanol that can damage plants. Break these piles up and allow them to dry out before using the mulch.
Various slime molds, like “dog-vomit” fungi and stinkhorn fungi, may be observed now growing in mulch. Although not harmful to plants, they are unsightly and can be broken up, turned under, or removed.
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