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Throughout the United States, many state and local governments place restrictions on the use of potable water for irrigating turfgrass landscapes. For many golf course superintendents, use of reclaimed, or other secondary water sources is the now the norm. Unfortunately, much of the recycled water used for irrigation contains high concentrations of dissolved salts that are potentially toxic to turfgrasses. More importantly, the use of effluent or reclaimed water sources often precedes the loss of soil structure resulting from the effects of high levels of sodium, bicarbonate and carbonate salts.

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Sodium Affected Soils

Sodium exists in nearly all irrigation water. High concentrations of sodium in irrigation water can be detrimental to both turf and soils. If water with levels of sodium that exceed 70 ppm (>70 mg/L) and low calcium and magnesium is applied frequently to clay soils, the sodium will tend to displace calcium and magnesium on clay particles. As the amount of exchangeable sodium in a soil increases, clay particles become increasingly unstable, leading to a disruption of the soil structure.

Problems with Bicarbonates and Carbonates

Of all the mineral constituents in irrigation water, bicarbonates and to a less extent carbonates are often underestimated in terms of their potential to synergize soil degradation and disrupt water movement through soils.

Carbonates greatly complicate the management of excessive Na. Their reactions reduce the amount of free calcium and magnesium in soil, allowing sodium to displace calcium from the negatively-charged exchange sites on clay particles. As the amount of exchangeable sodium in a soil increases, clay particles become unstable, leading to a disruption of the soil structure (deflocculation) and blocking of pores of a soil.

Amending Water

Today, many soil scientists recognize that poor water penetration is directly caused by a chemical imbalance in the soil and irrigation water. Their recommendations now suggest that many cases involving soil deterioration should be addressed by first amending the irrigation water or treating soils with amended water in an effort to reduce the carbonate threat in irrigation water and in soils.

This order of correction does not imply that soil amendments be abandoned. However, since the problem of sodium affected soils goes beyond correcting abnormal carbonate levels, using soil amendments containing calcium is usually required.