[by John Taberna, Western Laboratories, Parma, Idaho]
Soils have two properties that are mostly affected by salts: physical and chemical. Both of these have distinct characteristics. The two physical problems affecting soil structure are crusting and cementing.
CRUSTING is where the soil surface is dispersed by water from rain or irrigation. Upon drying, the surface forms a hard crust. Since most young seedlings do not have the energy to break through the crust, they die. Crusting is a surface problem, and it is only the surface that needs treatment. Any soil amendment should be applied at planting or thereafter.
Table 1. Guideline for CRUSTING
When used, the following products should be applied in a 3 to 4 inch band directly on the surface soil over seedpieces for crusting problems.
-- Elemental sulfur takes up to three years to oxidize to sulfuric acid. It may not be at concentrations high enough in the soil crust to be effective. Therefore, elemental sulfur is not a good crusting treatment product. (Rate = 100 to 200 lbs/acre).
-- Gypsum is an excellent product for treating crusting soils. Gypsum is generally applied at the wrong time, and that is a problem. Gypsum should be used only when there is no lime and the calcium levels are below 1500 ppm-Ca. (Rate = 400 to 600 lbs/acre).
-- Ironsul is effective on soils with lime, without lime, with calcium <4000 ppm, with calcium >4000 ppm, with sodium <230 and with sodium >230. It is the ideal treatment for crusting. (Rate = 150 to 200 lbs/acre).
-- Sulfuric acid and phosphoric acid are excellent products for treating crusting. For them to work, the soil must contain lime. (Rate = 60 lbs actual/acre).
-- Acid residue fertilizers are poor products for treating a crust problem on salt-affected ground. Their role in alkaline soils is to aid in the prevention of cementation of salt-affected ground.
-- Manure and green manure crops, if left close to the surface, will aid in the physical separation of silts and clays, preventing them from plating and causing a crust. (Rates = 2 inch thick manure/acre; disc green manure prior to planting).
-- Deep plowing can benefit the surface soil structure if a sandy material is turned up and mixed with the platy surface soil. This will reduce the surface crusting potential of soils high in silts and clays.
-- Other practices to be considered are: 1. fall irrigation of ground, 2. irrigation prior to planting and 3. warming of soils at 4 inch depth.