Cl in fertilizer for Crops

Some plants like grape, tobacco are called as chloride sensitive crops, and agronomist suggests that apply potassium sulfate (SOP) in place of potassium chloride (MOP).

The element chlorine is ubiquitous in nature, and occurs in aqueous solutions as the anion chloride (CI-). In this form it is also readily taken up by plants and average chlorine contents in plant tissues are in the range of 2-20 mg g-1 dry matter. In most plant species the requirement for optimal plant growth, however, is 10 to 100 times lower which means that chlorine is a typical micronutrient. Because it is usually supplied to plants as chloride from various sources (soil reserves, irrigation water, rain, fertilizers, air pollution), chlorine deficiency is rarely found. On the contrary, there is much more concern about chlorine toxicity world-wide. Plant species vary greatly in their susceptibility to high chloride concentrations in the soil solution and four main groups.

in this respect can be distinguished:

1. Chloride loving crops

2. Chloride tolerant crops

3. Partly chloride tolerant crops

4. Chloride sensitive crops

Chloride-loving crops include sugar beet, fodder beet, celery, asparagus and Swiss chard.

Chloride-sensitive crops include many fruit and vegetable varieties, and special crops such as hops or tobacco.

For these crops only fertilizers with potassium in sulphatic form should be used. The effects of high CI- concentrations in the soil solution on yields of various crops is shown in the following graphs. The steeper the yield decline with increasing CI- soil concentrations the more sensitive to chloride is a crop and hence the better will be the response to virtually CI- free fertilizers.

Prior to these substantial yield depressions, uptake of large amounts of chloride may lead to negative effects on crop quality such as:

Reduced content of organic acids, resulting in a flat taste

Accumulation of low molecular organic substances and thus decreased contents of valuable storage compounds (sugar, starch, protein)

Increase hydration of plant tissue and decreased storage or processing properties.

To avoid yield, quality and hence income losses in chloride sensitive and especially high value crops, where quality counts, the use of low chlorine potassium fertilizers