Healthy soil for a good harvest

Article by: Ted Rosen  |  Picture by: Ted Rosen
Healthy soil for a good harvest
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With proper soil preparation, adding compost and the right amount of fertiliser and following the rules of crop rotation, you can improve your yields and the health of your garden. This article describes the basics of soil amendments, soil texture, fertilising, mulching and crop rotation.

Adding organic amendments
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Adding organic matter, 'amendments', helps the soil. Compost is an ideal amendment for your garden. You can make your own compost from produce leftovers, garden waste, leaves and cut grass. To learn more, see the article on composting.
The amount of organic material you need to add to your soil depends on the condition and type of your soil. If your soil is heavy in clay or sand, you will need to add compost and loam. Loam is soil with a 40%-40%-20% mixture of sand, silt and clay. If your soil is already rich in humus and organic matter, you will need to add sand to improve drainage. Soils in a cool climate generally have more organic matter than those in a warm climate.
Check your soil texture
Properly prepared soil can be compressed in the palm your hand, and split in half easily by your thumb.
Measure soil fertility
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Soil fertility is measured by the pH scale. Soils below neutral (pH 7) are known as acidic (or, 'sour'). Soils above pH 7 are basic (or, 'sweet' or 'alkaline'). Most garden crops do well with a soil pH of 6.2 to 6.8 but some vegetables and small berries have different pH requirements. If the pH of your soil is too high or low, your crops will not grow well.
For acid soil below pH 6.2, ground agricultural lime is added to increase the pH, making the soil more basic. To know how much lime to add to your soil, follow the directions on the lime container.
Meter the pH
For the price of a shovel or less, pH and fertiliser meters are good investments.
Fertiliser alphabet: N, P, K
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Plants need 17 nutrients for normal growth, including nitrogen (N), phosphorous (P) and potassium (K). Nitrogen is responsible for strong stem and foliage growth. Phosphorous helps with healthy root growth and flower and seed production. Potassium improves overall plant health and disease resistance. Fertiliser is labelled by its percentage of N, P and K, plus any of the other 14 macronutrients and micronutrients.

Gardens need to be fertilised several times during the growing season. Most fertiliser is granulated and raked into dry soil. Some gardeners prefer fertiliser mixed in water or as a spray. Granules release the nutrients slower whereas liquid fertiliser provides a quicker fix for nutrient deficiency.

Whatever types you use: Take it easy! Not all crops need the same amount of fertiliser. You cannot fertilise for an entire growing season in one afternoon. Over-fertilising is harmful and counterproductive. It is better to use too little fertiliser, rather than too much. See the fertiliser 'feeding' requirements listed for each crop.
Always fertilise when dry
Fertilise the soil when the leaves of your plants are dry. If granulated fertiliser lands on a wet leaf it can burn and damage the leaf. Gently brush or wash it off.
Mulch: holds the moisture, stifles the weeds
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Mulch is any weed-free organic material used to cover the soil around your crops and the rest of your entire garden during the growing season to hold in moisture and to suppress weeds. If you don't mulch, watering and weeding can become a gardener's lament. The time spent mulching pays many times over in time and effort saved.
You can use any weed-free organic material as mulch, for example ground up bark, sawdust, straw (not hay which is filled with seeds), herbicide-free dried grass, shredded and sheets of newspaper or corrugated cardboard. Place the mulch on top of the soil to the depth of at least two or three thumb-widths.

Black plastic may also be used. Lay the plastic down securing the edges with soil or rocks before planting. Cut small slits with a utility knife in the plastic to plant. As the plant grows, enlarge the opening to make sure rain can penetrate to the roots, and allow you ready access when you water.
Musical chairs: Crop families and crop rotation
Crop rotation is a form of musical chairs among the crop families (listed below). Plants from the same crop family either deplete or add certain nutrients to the soil. You should only plant from the same family once every two years in the same spot.
Some plant families deplete the soil of nutrients; as heavy 'feeders' they require larger doses of fertiliser. Other plant families give back to the soil. By observing crop rotation, and keeping track from year to year what you plant where, you will keep your garden productive and healthy. See also fertiliser requirements for each crop.
Before planting or seeding plan your garden using the principles of crop rotation, using a different colour pencil to keep track by crop family. Keep your garden map as a reference for next year's garden layout planning.
Exception to the rule
Some fast growing crops like lettuce can be sown two or three times in the same location in the same season.
The major crop families
There are more than a dozen Crop families. We have focused on a small selective list of crop families that are most common in kitchen gardens. Crop families are grouped by their common names and put the scientific name in parentheses.

Carrot or parsley family (Apiaceae): Carrot, celery, celeriac, chervil, coriander, dill, fennel, parsley, parsley root, parsnip

Sunflower family (Asteraceae): Artichoke, chicory, dandelion, endive, escarole, Jerusalem artichoke, lettuce, radicchio, tarragon

Mustard family (Brassicaceae): Arugula, broccoli, Brussels sprouts, cabbage, cauliflower, collards, cress, horseradish, kale, kohlrabi, mustard greens, pak choi, radish, rutabaga, turnip, watercress

Goosefoot family (Chenopodiaceae): Beetroot, orach, spinach, Swiss chard

Bean family (Fabaceae): Bean, pea, edamame, fava beans, alfalfa

Morning glory family (Convolvulaceae): Sweet potatoes

Squash or melon family (Cucurbitaceae): Cucumber, melon, pumpkin, summer squash, watermelon, winter squash, courgette, marrow

Bean family (Fabaceae): Alfalfa, bean, edamame, broad bean, pea

Grass family (Gramineae): Sweetcorn

Mint family (Lamiaceae): Basil, marjoram, all mint varieties, oregano, sage, rosemary, thyme, lavender

Onion family (Liliaceae): Asparagus, chives, garlic, leek, onion, spring onions, shallots

Mallow family (Malvaceae): Okra

Nightshade family (Solanaceae): Aubergine, pepper, potato, tomato, tomatillo (husk tomato)

Valerian family (Valerianaceae): Corn salad / mache.
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