Effects of Soil SaltsSince roses are usually heavily fertilized, an accumulation of soluble salts is not uncommon. This could result in foliage injury and retarded growth. The effect of such salt accumulation is interference with water availability in the root zone. The higher the salt contents of the soil, the greater the stress on the plant to obtain moisture from that soil. Thus roses growing in soils having high salt concentrations tend to induce a physiological drought in the plants. This effect is intensified as the moisture content of the soil decreases.
All soluble salts do not have the same effect on the soil. Some present a more potent risk of injury by inducing physiological drought. Many of the high analysis fertilizer materials commonly used on roses are capable of producing a high salt index. However, when applied in suitable amounts for fertilizer response, the salt effect is usually not a problem.
A given concentration of soluble salts may not be injurious if the soil is kept moist and evaporation rates are low. But given the opposite conditions, the same salt concentration can cause root injury, which in turn cause wilting of shoots. All waters, except distilled, most rain or melted snow, contain some dissolved salts. Common components (ions) of salts contained in water supplies are calcium, magnesium, bicarbonate, chloride, fluoride and sulfate. Calcium, magnesium and potassium are plant nutrients, but can cause reduction in plant growth when present in excess of requirements.
Chlorides are especially injurious causing reduced plant growth and leaf drop. As the soil becomes solution becomes more concentrated. A concentration of dissolved salts, which is safe when the soil” moist, may become toxic when the soil becomes dry. It only takes one drying cycle under these conditions to cause the loss of roots, causing the plant to lose leaves.
The term salt index is used by scientists to indicate the relative physiological drought inducing effect produced by an equal weight of any fertilizer. Nitrate of soda, muriate of potash and ammonium nitrate are capable of inducing high salt effects when applied in any but moderate amounts. Other materials, notably the phosphates, ammoniated or otherwise, have a relatively low salt index.
It is important for the rose grower to appreciate the importance of water in the use of fertilizer material capable of inducing high salt effects. Small applications of water tend to dissolve the fertilizers and to develop the highest soluble salt concentration possible in the root area. Applications of water which cause some, but not too much, leaching tend to affect a loss of such materials as sulfates and chlorides, with little loss of ammonium or potassium, thus minimizing an increase of salts. Moreover, such watering gives good distribution of applied fertilizers. This is why one should never feed roses if the soil is dry and adequate watering should be done after fertilizing.
Where water is used conservatively, i.e.sub-irrigation, the salt concentration of the water supply is of the utmost importance. Because this method of watering is highly conducive to salt accumulation, sub-irrigation is not suitable for use with water supplies having more than low to medium amounts of soluble salts. If drip irrigation is used, the water supply should be tested for soluble salts. If the analysis is high, a watering system that delivers a greater quantity of water at one time should be considered. All soluble salts are not equal in the effects on rose plant growth when they are present in excessive amounts. Plants will tolerate relatively large amount of sulfates as salts of calcium and magnesium and even of potassium. Nevertheless, the treatment for the correction of high salt accumulations is the same- remove them with water. If drainage is not satisfactory, it may be advisable to add gypsum before leaching. Gypsum tends to improve soil aggregation and consequently the drainage of water. It is also very effective in displacing or facilitating the leaching of other salts from the soil. The liberal supply of calcium in gypsum exchanges places with other metal ions held in the soil and can be tolerated by plants to an unusual degree.
Growth retardation of roses from the effects of an excessive accumulation of soluble salts in the soil is indicated by electrical conductance tests on soil samples. A high salt index may not be as harmful in winter as in summer. Injury is most likely to result during hot, dry days of summer.
All soluble salts do not have the same effect on the soil. Some present a more potent risk of injury by inducing physiological drought. Many of the high analysis fertilizer materials commonly used on roses are capable of producing a high salt index. However, when applied in suitable amounts for fertilizer response, the salt effect is usually not a problem.
A given concentration of soluble salts may not be injurious if the soil is kept moist and evaporation rates are low. But given the opposite conditions, the same salt concentration can cause root injury, which in turn cause wilting of shoots. All waters, except distilled, most rain or melted snow, contain some dissolved salts. Common components (ions) of salts contained in water supplies are calcium, magnesium, bicarbonate, chloride, fluoride and sulfate. Calcium, magnesium and potassium are plant nutrients, but can cause reduction in plant growth when present in excess of requirements.
Chlorides are especially injurious causing reduced plant growth and leaf drop. As the soil becomes solution becomes more concentrated. A concentration of dissolved salts, which is safe when the soil” moist, may become toxic when the soil becomes dry. It only takes one drying cycle under these conditions to cause the loss of roots, causing the plant to lose leaves.
The term salt index is used by scientists to indicate the relative physiological drought inducing effect produced by an equal weight of any fertilizer. Nitrate of soda, muriate of potash and ammonium nitrate are capable of inducing high salt effects when applied in any but moderate amounts. Other materials, notably the phosphates, ammoniated or otherwise, have a relatively low salt index.
It is important for the rose grower to appreciate the importance of water in the use of fertilizer material capable of inducing high salt effects. Small applications of water tend to dissolve the fertilizers and to develop the highest soluble salt concentration possible in the root area. Applications of water which cause some, but not too much, leaching tend to affect a loss of such materials as sulfates and chlorides, with little loss of ammonium or potassium, thus minimizing an increase of salts. Moreover, such watering gives good distribution of applied fertilizers. This is why one should never feed roses if the soil is dry and adequate watering should be done after fertilizing.
Where water is used conservatively, i.e.sub-irrigation, the salt concentration of the water supply is of the utmost importance. Because this method of watering is highly conducive to salt accumulation, sub-irrigation is not suitable for use with water supplies having more than low to medium amounts of soluble salts. If drip irrigation is used, the water supply should be tested for soluble salts. If the analysis is high, a watering system that delivers a greater quantity of water at one time should be considered. All soluble salts are not equal in the effects on rose plant growth when they are present in excessive amounts. Plants will tolerate relatively large amount of sulfates as salts of calcium and magnesium and even of potassium. Nevertheless, the treatment for the correction of high salt accumulations is the same- remove them with water. If drainage is not satisfactory, it may be advisable to add gypsum before leaching. Gypsum tends to improve soil aggregation and consequently the drainage of water. It is also very effective in displacing or facilitating the leaching of other salts from the soil. The liberal supply of calcium in gypsum exchanges places with other metal ions held in the soil and can be tolerated by plants to an unusual degree.
Growth retardation of roses from the effects of an excessive accumulation of soluble salts in the soil is indicated by electrical conductance tests on soil samples. A high salt index may not be as harmful in winter as in summer. Injury is most likely to result during hot, dry days of summer.
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