Benefits Of Potassium Sulfate for Hydroponic Gardening

Potassium sulfate (K2SO4) also known as sulfate of potash, arcanite, or archaically known as potash of sulfur) is a white crystalline, non-flammable salt soluble in water. The chemical compound is commonly used in fertilizers, providing both potassium and sulfur.

The application of K (Potassium) in nutrient formulae depends upon its chemical combination with other elements that affects both crop quality and yield. Since potassium fertilizers are derived from natural products, they may contain substances other than K, S, and Cl that influence plant growth. Thus, choosing the right type of potash fertilizer can be as vital as applying the right amount of potash to the crop.

Potash fertilizers are two main types in which potassium is combined with either chloride or sulfate. Potassium sulfate and potassium chloride differ in their effects on plants. The potassium in a fertilizer exists as a neutral, acid, or alkaline salt in which the cation K+ is combined with an anion: CI or SO 4. When the plant takes up K ion, it also absorbs an anion to maintain electrical neutrality. Anions containing S, are incorporated in plant material thus losing their ionic form, but Cl remains in the ionic form. Thus the concentration gradient of Cl in the plant is less steep than that of the other anions. Moreover, certain crops are particularly sensitive to chlorine, and for these, the use of chloride-containing fertilizers should be avoided. Crops are also sensitive to salinity which is a serious problem particularly in arid areas; again, chloride should be avoided in such cases.

Also, sulphur is a major plant nutrient, and plants require a continuing and sufficient supply of sulfur of the same order as that for P. Therefore, Potassium Sulfate is an essential salt and an excellent source of K and S that cannot be missed from your nutrient channel.

Potassium Sulfate Uses

  • Sturdy stalk and stems
  • Resistance from drought and diseases
  • Enhances the quality of fruit
  • Strong roots
  • Activates enzyme reaction
  • Synthesis Proteins
  • Promotes thickness of outer cell wall
  • Improves color and flavor
  • Forms starch and sugar
  • Regulates water flow in cells and leaves
  • Potassium is an essential cofactor in the production of ATP

References

The effect of K nutrition on the growth in sand culture of young tomato plants, cv. Amberley Cross was examined, and the concentrations of K in the nutrient feed and  the leaves associated with maximum flower number, fruit set, and yield were determined. The distribution of K between and with-in fruit trusses of normal and K-deficient plants, cv. Amberley Cross and Moneymaker grown in peat/loam was also studied. Total dry weights of 6-wk-old plants grown in sand were maximal when the nutrient feed contained 0.53–5.03 me K+/l, although plants receiving 10.23 me K+/l retained more water in the foliage and therefore had the greatest foliage fresh weight. Both peduncle length and height of the basal truss were increased by K in the feed up to 10.23 me/l, the highest concentration used. Flower development was retarded below 0.53 me K+/l, and fruit setting efficiency was reduced below 2.03 me K+/l. Fruit ripened faster on plants receiving low concentrations of K. Maximum fruit yields were produced on plants grown in sand receiving 5.03 or 10.23 me K+/l.

Besford. R.T., Maw. G.A., 1975. Effect of potassium nutrition on tomato plant growth and fruit development. Plant and Soil. Volume. 42, No.2, pp. 395-412.

The growth and metabolism of plants in response to different concentrations of tissue K is discussed about current knowledge about the distribution and functions of this ion in plant cells. In the cytoplasm, K has an important role in providing the correct ionic environment for metabolic processes. The ionic requirements of protein synthesis seem to be particularly important in determining the composition of the cytoplasm. Potassium is not replaceable in its cytoplasmic functions and the plant probably needs to maintain the cytoplasmic concentration of K in the range of 100 to 200 mM. Potassium salts in the vacuole are involved in the generation of turgor but when unavailable they can be replaced by other solutes.

Leigh. R.A., Jones. R.G., 1984. A hypothesis relating critical potassium concentrations for growth to the distribution and functions of K ion in the plant cell. New Phytologist, Volume. 97,  Issue. 1,  pp. 1–13.

Potassium is the most abundant cation in higher plants and is crucial for plant nutrition, growth, tropisms, enzyme homeostasis and osmoregulation. K+ accumulation can be rate-limiting for agricultural production. K+ uptake from soils into roots is widely mediated by high-affinity K+ uptake (Km approximately 10-40 microM) (refs 1, 2, 5-7). But although K+ channels allow low-affinity K+ uptake, both the transport mechanism and structure of the high-affinity K+ nutrition pathway remain unknown. Here we use expression cloning to isolate a complementary DNA encoding a membrane protein (HKT1) from wheat roots which confer the ability to take up K+. The substrate affinity, saturation and cation selectivity of HKT1 correspond to hallmark properties of classical high-affinity K+ uptake in plants. The transport mechanism of HKT1 uses K(+)-H+ co-uptake. Expression of HKT1 is localized to specific root and leaf regions which represent primary sites for K+ uptake in plants. HKT1 is essential for plant nutrition and could contribute to environmental alkali metal toxicities.

Schachtman. D.PSchroeder. J.I.,1994. Structure and transport mechanism of a high-affinity potassium uptake transporter from higher plants. Nature.  Volume. 370., No. 6491., pp. 655-8.

The benefit of potassium (K) as a soil fertilizer to increase yields of crops has been known for several hundred years:

Can Potassium Application Affect the Mineral and Antioxidant Content of Horticultural Crops? Fertilizing Crops for Functional Foods: Symposium Proceedings. 2002

In another study, cotton plants receiving K fertilization yielded more than plants that did not receive K. The cotton yield increased an average of 9% during these 2 yrs. This larger boll mass was due to more seed per boll, greater seed mass, and more lint/seed. Thus, K addition showed overall increase in yield of cotton:

Relationships between Insufficient Potassium and Crop Maturity in Cotton – Cotton. Agronomy Journal. (2003). 95, 1323-1329.

Traynor, J. “Making ‘K’ Pay in your Vinyard: Dripping Potassium Carbonate into the System.” BeeSource. 2002.

The influence of the level of potassium supply on the incorporation of labeled nitrogen (15N) was studied in young tobacco plants. During a 4-h period the plants, which were well supplied with potassium, absorbed a greater amount of labeled nitrogen and utilization of this nitrogen for the synthesis of organic nitrogen compounds occurred more rapidly. The results clearly indicate that in the plants with lower K supply soluble amino acids accumulated whereas in the “+K” plants the incorporation of amino nitrogen into the protein fraction was accelerated:

Klaus Koch., Konrad Mengel., 1974. The influence of the level of potassium supply to young tobacco plants (Nicotiana tabacum L.) on short-term uptake and utilization of nitrate nitrogen (15N). Journal of the Science of Food and Agriculture, Volume 25, Issue 5, pages 465–471.

Sulphur

In plants, the amino acids cysteine and methionine contain most of the sulfur. The element is thus present in all polypeptidesproteins, and enzymes that contain these amino acids. Disulfide bonds (S-S bonds) formed between cysteine residues in peptide chains are crucial in protein assembly and structure. These covalent bonds between peptide chains confer extra toughness and rigidity.

Many essential cellular enzymes use prosthetic groups ending with -SH moieties to handle reactions involving acyl-containing biochemicals: two standard examples from primary metabolism are coenzyme A and alpha-lipoic acid. Two of the 13 classical vitamins, biotin, and thiamine contain sulfur, with the latter being named for its sulfur content. Sulfur plays an important part, as a carrier of reducing hydrogen and its electrons, for cellular repair of oxidation. Reduced glutathione, a sulfur-containing tripeptide, is a reducing agent through its sulfhydryl (-SH) moiety derived from cysteine. The thioredoxins, a class of small protein essential to all known life, using neighboring pairs of reduced cysteines to act as natural protein reducing agents, to similar effect.

Nelson, D. L.; Cox, M. M. (2000.). Lehninger, Principles of Biochemistry (3rd ed.). New York: Worth Publishing.

Conclusion

The lack of potassium stunts plant growth and lessen the capability of plants to resist against drought and diseases.  Therefore, it is important for the crops to be supplemented with potassium at their growing stage. On the other hand, potassium sulfate is an excellent source of potassium as it provides potassium in a stable condition at neutral pH and is significantly added to improve the yield and quality of crops lacking an adequate supply of essential nutrients.

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