Soil salinityis a term that describes the excessive accumulation of mineral s alts in the soil. The problem of soil salinity concerns both urban gardens as well as rural and post-industrial areas. This process, in the long run, leads to the death of plants due to disturbance of their water management. We explainhow soil salinity is formed , what is the effect of soil salinity on plants andhow to reduce soil salinityin your own garden.
Soil salinity. Taking soil samples for testing
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Soil salinity - what is it and how is it formed?
Soil salinityis the term for the excessive accumulation of sodium, potassium, magnesium, chlorine, sulfates, carbonates and bicarbonates. It is estimated that soil salinity concerns 7% of the Earth's surface, while in Poland the soil salinity index may be even higher.A measure of the salinity of soilsis the weight content of s alt in a unit of the volume of soil water. It is expressed in grams per liter of water.
The salinity of the soil can be caused bythe natural accumulation of s alt in the soil or the result of inappropriate human activity leading to the formation of s alty soils.
Mainreasons for soil salinityin Poland are:
- using too high doses of mineral fertilizers in agricultural areas and in greenhouse crops
- watering plants with water with an excessive content of cations and anions: Na, Cl, NO2, K, SO4,
- use of s alt (sodium chloride) for snow removal and ice removal in winter,
- soil devastation in post-industrial areas.
Soil salinity - effect on plants
In excessively saline soils, the water management of plants is disturbed.It is difficult for plants to extract water and mineralsfrom s alty soil, even though these nutrients are present in the soil. The resulting oxidative stress, i.e. physiological drought, results inbrowning, drying out and premature fall of leavesIt also leads to a reduction in germination capacity, CO2 assimilation, and as a result to lower chlorophyll content in leaves and inhibition of plant growth.
Young seedlings are most sensitive to soil salinity
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The sensitivity of plants to soil salinitydepends on many factors, including the species and even the plant variety, development phase, and climatic and soil conditions. Young seedlings are most sensitive to soil salinity. Over time, the plant builds up defense mechanisms.
plants resistant to the salinity of the substrateinclude, among others: sea buckthorn, barberry, sumac, field maple, hawthorn, privet, Siberian caragana, cotoneaster, tamarisk, fodder and sugar beet, clover and barley .
Especiallysensitive to the s alt content in the soilare garden ferns, conifers, azaleas, rhododendrons, as well as many fruit trees and shrubs and vegetables.
Soil salinity measurement
Soil salinity is determined in laboratoriesby conductometric method, i.e. by measuring the electrical conductivity of soil paste obtained by mixing soil with distilled water. For gardening purposes , a portable conductivity meteris used for measurements, and the s alt concentration in soils and substrates is given in g NaCl per 1 dm³ of soil.
How to prevent soil salinity?
To prevent excessive salinity in the soil , first of all, use mineral fertilization in a rational way, avoid the use of s alt in winter maintenance of roads and paths, and use organic fertilizers to improve the soil structure .The recommended organic fertilizers include compost, manure (both fresh, composted and available in gardening stores, granulated cattle manure and chicken manure), and biohumus.
How to reduce soil salinity in the garden?
The salinity of the soil can be loweredstarting with liming the soil with the use of calcium-magnesium fertilizers. You can use e.g. granulated chalk lime with magnesium or dolomite.
In the case ofsaline soils at shallow depthsit is enough to perform deep plowing.
Reclamation of more severely degraded soil begins withplanting salinity-resistant plantsuntil soil permeability is gradually improved. In particularly severe cases, dilute sulfuric acid is used to dissolve the calcium carbonate in the soil. In practice, it increases the permeability and aggregation of the soil, and the sodium sulphate formed in the soil solution is washed away.
In agriculture,modification of cultivation methods on saline soilsFor example, in irrigated fields, plants previously grown at the tops of furrows are planted halfway up. This allows the roots to use up the water, while the s alt accumulation is strongest in the upper part of the ridge, away from the root system.
Irrigation of crops not only meets the needs of plants, but also maintains the gravitational flow of water in the soil andremoves excess s alt from the root zoneIf there is a lot of water, harmful compounds will be washed into the ground, i.e. where will not be accessible to plant roots. However, it is not easy to do, as very large amounts of water are needed - even 100-250 liters per 1 m². Therefore, this method is most often used in professional greenhouses.
On soils with poorer permeability , salinity can be reduced by adding organic matterthat is poor in digestible forms of minerals.Such an additive can be garden peat, uncomposted garden bark, softwood sawdust, beech bark compost, straw or mixtures of various fractions of brown coal. Depending on the level of soil salinity, use approximately 10-50% of the organic matter per 20 cm layer of soil.
MSc Eng. Anna Błaszczak
