saline soil formation

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Presentation Transcript

Slide1: 

Salinity/sodicity accumulation of Na+ in the solid ! ! ! and/or liquid ! phases of the soil exch. Na+: ESP (sodicity) soluble salts (salinity) alkalinity (highly alkaline pH) ! Limited fertility: physiological: limitations in water nutrient toxicity (special ions unbalanced metabolism) physical: extreme moisture regime !! uptake

Salinity/sodicity are risks to:: 

Salinity/sodicity are risks to: plant life (soil fertility, agricultural productivity: cultivated crops and their biomass yield; natural vegetation/ eco-systems); life and function of soil biota (biodiversity); soil deterioration (increased erosion potential, desertification, structure destruction, aggregate failure, compaction); hydrological cycle, moisture regime (increasing hazard –frequency, duration, severity – of extreme moisture events as flood, waterlogging, over-moistening and drought); biogeochemical cycles of elements (plant nutrients, pollutants, potentially harmful elements and compounds)

The preconditions of salt accumulation 1. : 

The preconditions of salt accumulation 1. Salt sources Local weathering Surface water Subsurface waters Human activities Transporting agents Wind, water Horizontal transportation: large watershed with small accumulation area Vertical transportation: geological strata to accumulation horizon

The preconditions of salt accumulation 2. : 

The preconditions of salt accumulation 2. Driving force to transport relief for surface runoff suction gradient for seep in the unsaturated zone hydraulic gradient for groundwater flow concentration gradient for solute transport Negative water balance (at least for certain period of the year) Vertical and horizontal drainage limitations

Environmental (natural) factors result in salinisation/sodification:: 

Environmental (natural) factors result in salinisation/sodification: movements of transgression and regressions that in some particular geological conditions bring about an increase of the concentration of salts in groundwater and consequently in soils; rise of salt-rich groundwater due to natural factors or human interventions up to the surface, near to the surface or to the overlying horizons; groundwater seepage into areas lying below sea level, microdepression with no or limited drainage; floods coming from areas with geological substrates that release high amounts of salts; wind activities that, in coastal areas, bring moderate amounts of salts in soils.

Human-induced factors may lead to salinisation/sodification:: 

Human-induced factors may lead to salinisation/sodification: irrigation of waters rich in salts; rising water table due to human activities (filtration from unlined canals and reservoirs; uneven distribution of irrigation water; poor irrigation, practice, improper drainage); use of fertilizers and amendments, especially in situations of intensive agriculture with low permeability and limited possibilities of leaching; wastewater disposals and wastewater irrigation; contamination of soils with salt-rich waters and industrial by-products.

Natural characteristics of the area: 

Natural characteristics of the area climate (temperature, rainfall, evaporation, wind characteristics, with their spatial distribution and time variability); geology (potential salt sources, sequence and thickness of aquifers and the vertical and horizontal transmissibility of geological layers); relief; vertical and horizontal drainage conditions; hydrology (quality and quantity of surface waters, groundwaters, deep waters and their fluctuations)

Natural characteristics of the soil: 

Natural characteristics of the soil texture; clay mineral composition; structure (aggregate status and stability; cracking, shrinkage – swelling characteristics); compaction rate – porosity (preferably differential porosity and pore-size distribution); hydrophysical properties (infiltration rate, water storage capacity, water retention, saturated and unsaturated hydraulic conductivity); salinity indicators (profile, regime, balances and ion composition of salts); sodicity indicators (pH, SAR, ESP).

Slide9: 

Secondary salinization Secondary salinization and alkalinization process may take place mainly in the following situations: Accumulation of salts from irrigation water of poor quality. Increase in the level of groundwater. The salt content of the groundwater accumulates in the affected layers; the rising groundwater transports the salts from the deeper soil layers to the surface or surface layers, or the rising water table limits natural drainage and hinders the leaching of salts.

Possibilities of salinity control: 

Possibilities of salinity control Leaching and drainage Preconditions Reversible processes (low Na+ saturation, moderate physical deterioration) Adequate amount of good-quality water Good vertical drainage of the soil profile (light texture, good hydraulic conductivity, Cl-SO4 type salinization, low alkalinity, low ESP) Good horizontal drainage of the area frost-free period after the vegetation season Drain water reservior Prevention ! ! ! Quality control of irrigation water Stabilization of ground water table Prevention of rise Lowering Saline seep-control

The „rational” use of salt-affected lands:: 

The „rational” use of salt-affected lands: Production concept: - improvement/reclamation/amelioration of salt-affected lands; - prevention (or at least radical reduction) of salinisation-sodification processes; - increasing the fertility/agricultural productivity even with high investments and input applications. Conservation/protection concept: conservation of the present state or re-establishment of a desirable previous natural (or at least near to natural) state: saline lakes, wetlands, saline lands with special ecosystems (flora, fauna, biotop)  national parks, protected areas, gene-reservoirs, man and biosphere reservatums.