How To Reduce Soil Acidity

2024 Author: Sebastian Paterson | [email protected]. Last modified: 2023-12-16 13:47

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With increased acidity, the growth of roots slows down, their branching stops, the number of root hairs decreases, the roots thicken, become more coarse and become somewhat slicker, the flow of phosphorus into plant roots is inhibited. Plants grown in acidic soils are more affected by pests and diseases, and harvested products are less well stored.

To establish the dose of lime, the acidity of the soil is determined, taking into account the biological characteristics of the crop, the applied fertilization system and other factors. To reduce the acidity of the soil, it is limed by adding wood ash, dolomite flour containing calcium and magnesium, as well as crushed chalk and shell rock, hydrated lime.

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On strongly acidic soils, liming is carried out gradually, since the change in acidity takes time. Therefore, autumn, winter or early spring is the best season for liming. The introduction of slaked lime will be effective in 2-3 months, but the added chalk or ground limestone will give results only after six months.

Lime fertilizers are applied to the soil on average once every 4-5 years. On lighter soils, lime is applied after 3-4 years, and on heavy soils - after 5-6 years. The finer the grinding of limestone, the stronger its effect. Ground limestone, dolomite flour, tuff and all types of plant ash can be applied to the soil with manure. First, lime fertilizers are spread evenly over the site, and then manure. The soil is dug up on the same day.

Slaked lime, cement dust, ground blast furnace slag, shale ash, etc. are also good materials for reducing soil acidity. But these materials contain caustic calcium compounds, which cannot be applied simultaneously with manure, since a large amount of nitrogen is lost from the manure. When applying manure in autumn, lime materials are applied in spring and vice versa. In addition, the amount of applied substances varies depending on the type of soil. Therefore, acidity correction cannot be expected to be accurate. The table below shows the doses of lime materials required to reduce the acidity of the soil by 1 pH up the scale (addition per 1 square meter).

Doses of lime materials

Soil type	Ground limestone (g / sq.m)	Slaked lime (g / sq.m)
Sandstone	220	160
Loam	300	230
Alumina	440	310

Doses of chalk during liming are also different and depend on the crop grown, the lime material used, the degree of acidity, and the mechanical composition of the soil. Below is a table showing the doses of chalk depending on the type of soil.

Chalk doses

Soil	Doses of chalk, kg / m², at pH values
	Up to 4.5	4.6	4.8	5.0	5.2	5.4-5.5
Sandy	0.30	0.25	0.20	0.15	0.10	0.10
Sandy loam	0.35	0.30	0.25	0.20	0.15	0.15
Leko loamy	0.45	0.40	0.35	0.30	0.25	0.25
Medium loamy	0.55	0.50	0.45	0.40	0.35	0.30
Heavy loamy	0.65	0.60	0.55	0.50	0.45	0.40
Clayey	0.70	0.65	0.60	0.55	0.50	0.45

The doses of chalk given in the table are usually referred to as total doses. They are designed to reduce the acidity of soils with normal moisture to a pH of 5.6-6.0, i.e. to a level that is optimal for many crops. On soils, excessively moistened, the dose of lime material should be increased by 0.1-0.15 kg / m² in excess of those given in the table, and on heavier ones - by 0.15-0.20 kg / m². Liming of peat-boggy soils has its own characteristics. The acidity values established for soils with a low organic matter content are unsuitable for peat soils. The need for liming of such soils is considered strong at pH less than 3.5, medium - pH 3.5-4.2, weak - pH 4.2-4.8 and absent at pH 4.8. If the need is strong, you need to apply 300 g / m², medium - 200 g / m² and weak - 100 g / m² lime.

If wood ash is introduced into the soil, spruce is taken twice as much as lime or chalk, and birch and pine - one and a half times. Furnace ash can be used on all soils and under any plants. Ash can be applied as the main fertilizer in the fall before plowing or for digging, or in the spring in preparation for the planting season, as well as a local fertilizer in planting holes. When introduced into planting holes, it is mixed with humus, peat and manure.

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Liming acidic soils enhances the effectiveness of green fertilizers (green manure), especially when they are incorporated at the same time. However, adding lime without special need, especially on sandy soils, should not be carried away. This makes many microelements inaccessible to plants (they dissolve well in acids and precipitate in an alkaline environment). At the same time, artificial drought appears in the soil. The following measures contribute to a slight increase in acidity: the introduction of mineral fertilizers, manure, peat and compost in the course of soil cultivation. Below is a table showing the increase in acidity by 1pH (addition per 1 m²).

Acidity increase table

Ammonium sulfate	70 g
Gray color	70 g
Peat	1.5KG
Compost	9.25 kg
Manure	3 kg

During life, the pH level in the substrate changes. The plants themselves change the pH to a certain extent by means of root secretions. Watering with hard water lowers the acidity, and soft water increases it. In addition, fertilizers affect pH. Calcium nitrate increases the pH, and ammonium sulfate, potassium chloride, and urea acidify the medium with annual use, decreasing the pH.

With liming, light loose soils become more coherent, and heavy ones looser, their water permeability increases, and processing conditions improve. Liming enhances the activity of microorganisms that directly assimilate nitrogen from the air or through the nodules on the roots of plants, and microorganisms that decompose humus, thereby improving plant nutrition.

Plants treat soil acidity differently. On this basis, they are divided into four groups:

1. Plants that do not tolerate high acidity and most strongly respond to soil liming

(beets, cabbage, onions, garlic, celery, parsnips, spinach, currants, plums, cherries, ornamental cabbage, levkoy, roses, chrysanthemums, ageratum, kochia, aster, etc.).

2. Plants that need a slightly acidic and close to neutral soil reaction that respond well to liming

(cauliflower, kohlrabi cabbage, lettuce, leeks, cucumbers, rutabagus, pear, apple tree, strawberry, asparagus, amaryllis, alternantera, rose hips, beans, tradescantia, bell, pelargonium, primrose, radish, zucchini, Brussels sprouts and leafy cabbage, turnip, eggplant, chokeberry, chicory, apricot, grapes, lilacs, chrysanthemums, crocuses).

3. Plants that do not tolerate excess calcium, under which only on strongly and moderately acidic soils it is necessary to make reduced doses of lime

(potatoes, carrots, parsley, radish, tomatoes, radishes, gooseberries, raspberries, azalea, calla lilies, monstera, fern, acroclinum, sunflower, melon, corn, panicle hydrangea, cherry, apple tree).

4. Plants that are insensitive even to increased acidity of the soil, weakly responsive to liming

(sorrel, lupine, hydrangea, seradella, Japanese maple, large-flowered magnolia, Japanese andromeda, Japanese skimmia, Erica, some types of lilies, horsetails, cranberries, cloudberries, heather, rhododendrons).