EVSC-220 Salinity

Salinity

What is salinity?

Amt of soluble salts in soil

Salt: cation (other than H) and anion (other than OH)

What is a saline soil?

high in salts

low in Na+

What is a sodic/solonetzic soil?

High Na+ hard pan layer

usually saline subsoil, restricts root growth

Ah-Bnt-Csa/Cca

What is an alkali soil?

low in soluble salts

high Na+ and pH

What are the major salts in soil?

Soluble: Sulfates, Na and Mg chlorides

Insoluble: lime and gypsum

What chemical properties create sodicity?

Na’s lrg hydrated radius disperses clay

Limits porosity and root penetrability

What do you use to measure sodic soils?

Penetrometer measures resistance to penetration

Determines if hardpan layer

Wetter soils have higher penetration resistance

What are the impacts of salt-affected soils?

Lowers ag productivity, water quality, soil biodiversity

Increases erosion and toxic ion concs

Degrades structure, cycling, water uptake, fertility

What are the 3 major issues for plant growth from salinity?

Toxicity of Na, Cl, B

Ionic imbalances interfere w metabolism

Physiological drought

How does physiological drought work?

Sap in roots attracts wtr by osmotic pressure

Dissolved salts increase osmotic pressure of soil sol’n, decreases rate of wtr entering roots

If salt conc too high plants starve, even if enough wtr in soil

What are the sources of salinity in soils?

Natural: primary minerals (PM), atm, sea wtr intrusions, grdwtr discharge

Anthro: irrigation, fert, road salt, mining operations, oil drilling wastewtr

What are the primary sources of salinity in ag soils?

Artesian discharge: P in aquifer high enough to force wtr to surface

Evaporitic rings around sloughs: deep drainage impeded; high wtr table and evap

Side hill seeps: lateral wtr mvmt along impermeable surface

How does salinity develop in soils?

Dry climate (evap, not enough ppt to flush through profile)

Poor drainage (high wtr tbl, low permeability)

Irrigation (adding salts)

Mining (tailings, esp potash)

What are the principles of reclaiming saline soils?

Add good quality water (low EC and SAR) to leach salts out of rooting zone

Manage recharge area: prevent accum of wtr thru drainage/ag mgmt using more mstr (deep-rooted forages, alfalfa)

Manage discharge area: est crop growth and move salt down

Manure/org amendments: hi rates of manure, holds Na better (CEC) and improves wtr avail

Fert application: seed-app P increases wheat yield in saline soils, less N uptake from salts,

What are the principles for reclaiming sodic soils?

1. Physical disturbance of Bnt

2. Chem amendment to displace Na+

Tilling Solonetzes (deep), seeding and tilling at right mstr

• Dry: too hard to till

• Wet: structure bdown completely

What are the effects of applying gypsum to saline vs sodic soils?

Saline: none, already in it

Sodic: can improve structure by replacing Ca w Na on adsorption sites