What does Lime do to the soil?

• Lime neutralizes active (soil solution) acidity

• Lime also removes exchangeable Al⁺³ from clay cation exchange sites

Reasons for Liming Soils ?

Crop responses to Lime?

Name 3 benefits of Liming Soils ?

Explain what an alkaline soil is:

Soil bacteria convert sulfur to ________  ________.

sulfuric acid

A salt‐affected soil has accumulations of ______ and/or ______________ sufficient to harm plant growth

salt, sodium

Salts added to the soil in precipitation, by mineral weathering, or with irrigation water and fertilizers, accumulate in the soil profile unless they are leached below the ______ zone

Root

 Inadequate leaching is due to

•Inadequate water

•Compacted layers
• Heavy (clay) soils
• Sodium‐impacted soils

• High water table

What causes Salt‐Affected Soils?

In closed basins, water and dissolved salts _________.  The water evaporates, leaving the salts behind.

accumulate

What human causes created Salt‐Affected Soils?

– Irrigation without proper drainage
– Disposal of salty wastes
• Oil and gas exploration

Saline soils are affected by non‐__________ salts

sodium

_________ soils have high levels of sodium salts

Sodic

________ accumulation reduces productivity

salt

What happens when salt accumulates in the soil?

– Soils can become permanently unproductive

– Saline or sodic soils are expensive to reclaim

Ions in solution conduct electricity, so the total amount ofsoluble soil ions can be estimated by measuring the ___________ _________  of a soil water extract.

electrical conductivity

A __________ soil has an electrical conductivity in a

saturated paste extract of > 4 dS/m.  The high

conductivity is caused by high concentrations

of soluble salts

saline

Name all the salts found in saline soils  

cations Na⁺, Mg²⁺, and Ca²⁺,

and the anions Cl^‐, SO₄^2‐, and HCO₃^‐

The main adverse effect of salts is the

“_________ _______” of salts, reducing availability

of water to plants.

osmotic effect

When water is drawn away from regions of low salt concentration (high Ψs) inside the root and towards regions of high salt concentration (low Ψs) outside the root it is caused by the_________ ________. 

osomotic effect

Degree of flocculation affects what soil physical

properties?

• Water infiltration and drainage

• Porosity and aeration

• Penetrability by plant roots

Define dispersed

Soil clay particles can be unattached to one another

Define flocculated

Soil clay particles can be clumped together in

aggregates.  

In all but the sandiest soils, excess _______ causes clays to disperse

sodium

____________ clay plugs soil pores and impedes water infiltration and

soil drainage

Dispersed

_________ and ________ are mostly unaffected by Na⁺

sands, silts

Even though sodium is a weak ________________, it can ____________________

soil colloids if it is present in large enough amounts.

flocculator, flocculate

Soil particles will flocculate if concentrations of ________ _________ are increased relative to the concentration of Na+(SAR is decreased).

(Ca²⁺+Mg²⁺)

Soil particles will disperse if concentrationsof (Ca²⁺+ Mg²⁺) are decreased relative to the concentration of _______(SAR is increased).

Na⁺ 

Soil particles will _______ if the

amount of soluble salts in the soil is

increased (increased EC), even if

there is a lot of sodium.

flocculate

Soil particles can __________ if the amount

of soluble salts in the soil is decreased

(i.e. if EC is decreased).

disperse

If soils are close to the “tipping point” between flocculation and dispersion, the

quality of ____________ water will influence aggregate stability.  

irrigation

If irrigation water

infiltrates, and rain water does not, this indicates that the soil is close to the

“__________ ___________”.

tipping point

Name 4 things about Saline-sodic

excess salts

excess Na

good structure

high pH

Name 3 things about Sodic?

 excess Na

poor structure         

high pH (>8.5)

How do you reclaim saline soils?

Simply leach salts from the soil profile of saline soils

by applying excess water

– To leach salts, good internal drainage is a must

• Artificial drainage may be needed.

– Leach with a low‐salt water source

– Use a surface mulch to reduce evaporation

(Saline soils are not difficult to reclaim if they have

adequate drainage and there is a supply of suitable quality water)

How do you reclaim sodic soils?

Reclamation of sodic soils is more difficult

than for saline soils, because of their unfavorable structure

– Exchangeable Na+ must be replaced, preferably with Ca²⁺

• A source of Ca²⁺ (such as gypsum) can be added

• Soil CaCO₃ can be dissolved with H₂SO₄ or another acid

Reclaiming sodic soils:  

Controlling ______

requires increasing concentrations of soluble Ca²⁺

to decrease soil or water SAR,thus favoring soil flocculation.

Na⁺

Increasing soluble ________ improves aggregate stability in soils with poor structure.  

calcium

Apply __________ before leaching salts out of soils susceptible to dispersion 

gypsum

_________ _______ can be used instead of gypsum on calcareous (CaCO₃ containing) soil only

Sulfuric acid

Salt buildup is always a potential problem

when soils are ______________.

irrigated

The only way to manage salts in irrigated soils is

to _______them out with excessive application of

water

leach 

What lowers soil profile salinity by carrying excess

salts below the root zone

Leaching water 

The size of the leaching requirement depends on?

• the irrigation water salinity (Ecw)

• the tolerance of the plant to salt

The _____ ______, the excess water (above crop needs) that must be applied to keep salts at a level that will not reduce yield, increases as irrigation water salinity increases.

leaching requirement