Improving Your Soil
Healthy plants come from healthy soil. Make sure your garden is providing the right nutrients in the right proportions for optimum results; too much or too little of soil nuitrients can affect how well your garden grows.
The structure of your soil is important. Loose, cumbly soil that contains organic matter will allow plants roots to grow deeper, provide nutirents, channel water to pant roots and hold water more easily.
Healthy soil will also contain micro-organisms that convert organic matter into nutrients plants need to grow
What is Healthy Soil?
Healthy soil contains the right proportions of air, water, minerals and organic matter that plants need for growth.
Soil Structure This determines how water drains and is held in the soil, the amount of air space, and if nutrients are easily released for use by plants. Add organic matter to improve soil structure: 1 inch of fine compost or manure each year, 3 to 4 inches of bulkier materials like straw or leaves. (Turn leaves, other non-composted material into your garden in the fall, so it will hav ebroken down by the time you plant in the spring.) Avoid compacting soil by walking on your garden beds, or working soil whenit is wet.
Nuitrients Plants need macro-nutrients like nitrogen, phosphorus, potash (the N-P-K in fertilizers) calcium, magnesium and sulfur to thrive and other minerals in smaller amounts (iron, manganese, copper, zinc and others). The availability of nutrients in the soil is affected by ground and air temperatures, moisture levels and soil pH. Organic fertilizers slowly break down in the soil make nutrients available to plants as they need them.
About pH Plants require certain ranges of acidity-alkalinity (pH). A 5.5 to 7.5 pH range allows essential nutriehnts to be available to plants. In general, soils in Minneapolis are alkaline, and city water is a pH near 8. Organic materials such as conifer needles, sawdust, peat moss and oak leaves will slowly help to acidify your soil.
Have your soil tested by the University of Minnesota Soil Testing Lab (information: 612 625-3101) to determine the percentages of nitrogen, potassium and phosphorus present in your garden, amount of organic matter and its pH. Add amendments to your soil to replace missing nutrients.
ORGANIC FERTILIZERS
Apply dry organic fertilizers in spring before planting, in amounts recommended by your soil test results. Spread evenly over your garden and work them into the top 4 to 6 inches of soil. Common orgnanic sources of macro-nutrients are:
- Nitrogen: Cottonseed meal, alfalfa meal, blood meal, fish emulsion and fish meal, soybean meal, animal manure, coffee grounds.
- Phosphorus: Bonemeal, phosphate rock.
- Potash Granite dust, greensand, kelp meal, wood ashes.
- Calcium: Eggshells, gypsum, limestone.
- Magnesium: Epsom salts, limestone.
COMPOST
Compost is a combination of organic matter that is decomposed to form humus. It improves soil structure, helps retain mositure and contains a balance of macro-nuitrients. Add 1 inch of fine compost each season (a little more if your need to improve soil structure) or use compost as a mulch. Make "compost tea" to feed plants when you water.
ANIMAL MANURES
Animal manures provide nutrients and organic matter. They must be well composted before using in the garden, or risk damaging your plants. Make "manure tea" to feed your plants when you water.
Using Cover Crops to Fertilize
Cover crops, also known as green manures, are any green plant tilled back into the soil. Cover crops can add nitrogen and organic matter to the soil, catch nutrients and moisture that have leached deep into the soil, loosen compacted soil and reduce soil erosion over winter. They may be planted in late summer/early fall to mature in the following spring, or sown as a living mulch. See Using Cover Crops
Mulches
A mulch vocers the soil, moderating temperatures by insulating the soil from extreme heat and cold, preventing erosion, retaining soil moisture, and improving soiol structure. Mulches help keep crops clean and disease free, and act as a weed barrier.
When mulches are made from organic materials, they will gradually add nutrients and organic matter to your soil. Adding a 3 to 6 inch layer of mulch to soil that has been thoroughly weeded will discourage weeds from growing. Mulches made from wood chips or sawdust tend to remove nitrogen from the soil as they break down. Mulches from non-organic materials like plastic provide better weed control, but do not allow healthy air exchange in soil, may build up heat, or not allow for sufficient water to pass through.
- Organic Mulches Straw, leaves, grass clippings, compost, composted manure, wood chips, sawdust, pine needles.
- Non-Organic Mulches Plastics, weed barrier fabric, stones or gravel.
More About Compost
Make compost in your garden or backyard from plant waste and food scraps. Combine "green" materials (higher in nitrogen) with "brown" materials (higher in carbon) in the right proportions, add water and let microorganisms such as bacteria and fungi break down your plant wastes. Layer green and brown materials, with a little soil between layers, and water so pile is the consistency of a wet sponge. Periodically turn the layers with a pitchfork to provide air and speed decomposition. A properly constructed and maintained compost pile will not smell. Your compost is ready to use when it looks like soil.
- Green Materials Grass clippings, green plants, vegetable peelings.
- Brown Materials Leaves, straw, woody plants, dry dead plant matter (from healthy plants; don't put diseased or insect infested plnats into the compost), pine needles, sawdust, woodchips.
- Other Materials to Add Coffee grounds, eggshells. -- bones, dairy products, fats and oils, grease, meat, pet feces, plastic or synthetic fibers. City of Minneapolis Ordinance prohibits these materials in home composting bins.
- DO NOT ADD Bones, dairy products, fats and oils, grease, meat, pet feces, plastic or synthetic fibers. City of Minneapolis Ordinance prohibits these materials in home composting bins.
More information on constructing a compost bin and making compost may be found at Minneapolis Solid Waste and Recyling.
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