_Soil Salts

Slide 1 Soil Salts problems in the landscape Slide 2 What is a salt? Combination of a negative ion (anion) acid with a positive ion (cation) base. eg: NaCl Sodium chloride CaCO3 Calcium carbonate MgSO4 Magnesium sulfate KCl Potassium chloride All soils contain salts. Many salts are plant nutrients Slide 3 Salt measurement Soil Salts expressed in terms of electrical conductivity (EC) EC measures the soil capacity to conduct an electrical current Expressed in deciSiemens/meter (dS/m) or milliSiemens/cm (mS/cm) Slide 4 Soluble salts vs insoluble salts Soluble salts are those that dissolve easily in water ( relative to gypsum CaSO4) Have the greatest effect on soil quality and plant growth. Slide 5 Salt terms to know Saline– high in salts (EC > 4mS/cm) Sodic – high sodium (pH > 8.5, SAR > 12) Slide 6 What contributes salts to the soil? Saline bedrock Saline groundwater https://www.anda-chem.com/2019/03/29/saline-alkali-soil-reclamation-suggestion-to-imran-baloch-from-nawabshah-sindh-pakistan/ Slide 7 What contributes salt to the soil? de-icing salts in winter irrigation practices bio-solids composted from sewage sludge can contain high levels of salt Slide 8 De-Icing Salts Once the temperatures warm up in the spring plants try to absorb water but this is limited by the salt concentration Slide 9 De-Icing Salts (spray) Slide 10 Fertilizers Fertilizers can contain a lot of salt so check the salt index: ≤ 25 is Low > 50 in sandy loam soils and >75 in silty clay loam soil are High Slide 11 Excess Salts ….. may break down soil structure and aggregation of the surface soil particles (sodium) creates surface crusting reducing infiltration (sodium) destroys microbial life causes decline and death, particularly in trees Slide 12 Soil Salts - signs Arid regions where evaporation exceeds rainfall: salts build up on the surface (from evaporation of capillary water) Slide 13 Salt & Climate most severe in irrigated soil water dissolves salt in the soil and fertilizer as the soil dries out, the salts are left behind Slide 14 Salt & Climate salts can accumulate to toxic levels flush the soil with high quality water to lower the salt levels if the dissolved salts can DRAIN out of the soil Slide 15 Soil Salts - signs if absorbed by the plant, may cause leaf scorch or bud deformity Slide 16 Soil Salts - signs reduce the plant’s ability to take in water causing drought conditions Slide 17 Salt Tolerance in Plants Factors: type of plant type of soil time of year weather cycles when the salt is applied how quickly it is leached away the health of the plant before the salt application Slide 18 Salt Tolerance in Plants Stressed tree confined, compacted soil may die from a small dose of salt Healthy tree growing in generous volumes of well-drained soil might not be affected by large dosages of salt Slide 19 nutrient deficiencies or salt damage? Slide 20 Trees: when to check salt levels A tree has a lot of dieback.... you take soil samples once these symptoms are noticed (Aug)... but results show low levels of salts??? Collect soil samples to determine salt concentration just before bud break.(over time, salts leach – so EC seems normal) Slide 21 Managing Salt Choose salt tolerant plants Develop well-drained soils by installing drainage systems a meter below the root zone or install deep, well draining soil Slide 22 Managing Salt use fertilizers with low salt indexes and reduce fertilizer use Apply mulch to the soil to reduce evaporation rates Slide 23 Managing Salt maintain irrigation to keep soil evenly moist - don’t allow to dry out Do not plant at the very tops of berms, ridges, where salts may accumulate Slide 24 Managing Salt design low curbs along edges of planting beds, lawns, and tree openings in sidewalks to divert sidewalk water away from the planting soil Slide 25 Managing Salt Increase soil volumes of planting areas to increase the health of the trees Slide 26 Managing sodium salts mix gypsum into the surface of sodium-salted soils before flushing with water Slide 27 Salinization the process whereby salts accumulate over time Slide 28 If more than 15% of the exchange sites are occupied by sodium the soil is sodic Soil structure is altered and there is a loss of mineral nutrients. Slide 29 Sodium replaces other ions that are important for plant nutrition Sodium causes deflocculation - disintegration of the soil structure and the production of fine particles that enter soil pore space. This reduces aeration and promotes soil compaction. Slide 30 Microorganisms Many microbes are sensitive to salt concentration AShigo Slide 31 Tree Age Older trees are less likely to suffer damage compared to younger trees - probably because of the extensive roots systems that older trees possess Slide 32 Heavy Metals Excess salinity will mean that sodium can mobilize heavy metal ions in the soil releasing them into the soil solution with the risk that they will be leached to streams and groundwater https://academic.oup.com/bioscience/article/68/5/327/4913800