Substitution of potassium by sodium in sugar beet (Beta vulgaris L.) : Nutrition with special reference to K-fixing soils
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Plant growth does not response to the application of generally recommended levels ofpotassium (K) fertilizer in the soils with expandable three layer clay minerals. In the soilsrich in illite and vermiculite clay minerals with high cation exchange capacity, a major partof applied K is fixed and becomes unavailable to plants immediately.It is known that several members of the family Chenopodiaceae such as sugar beet,spinach, red beet etc. are capable to use sodium (Na) as an osmoticum for which 95% oftotal acquired K is required. We hypothesized that Na is able to substitute K to a largeextent in sugar beet nutrition without affecting the plant growth and beet quality. Weassumed that in K-fixing soils it would be possible to replace a huge amount of K fertilizerwith adequate amount of Na fertilizer, which may lead to the development of an interestingfertilizer strategy for sugar beet in K-fixing soils. In this study, an attempt was made toidentify the limiting processes when K was substituted by Na in K-fixing soils.Three soil and two nutrient solution experiments were conducted to test the abovementionedhypothesis. In the first soil experiment, soils from three locations (i.e.Kleinlinden, Giessen and Trebur) with different K-fixing capacity were tested and sugarbeet plants were grown in Ahr pots under natural climatic conditions (April 2005 toSeptember 2005, Giessen, Germany) and harvested at maturity. Three treatments wereused i.e. control (no K and Na fertilizer), potassium treatment (K2SO4 fertilizer wasapplied according to K-fixing capacity of soil) and in third treatment NaCl was appliedequivalent to regular K fertilization. Soil Kleinlinden was tested again in anotherexperiment where sugar beet plants were grown in containers (169 kg soil container-1) withthe same treatments as in the previous Ahr pot experiment, except potassium treatment.Potassium was not applied according to K-fixing capacity of soil, rather according toregular K fertilization. A field experiment was conducted on the Trebur soil (similar to thesoil used in the Ahr pot experiment). The treatments were the same as in the containerexperiment; nevertheless an extra treatment was used where a huge amount (i.e. equivalentto half K-fixing capacity of the soil) of K was applied. The results of all the experimentsrevealed that application of Na fertilizer significantly improved the plant growth relative tothe control. However, white sugar yield in Na treatment was similar to that in K treatment.Moreover, Na eliminated the K deficiency symptoms in the plant leaves, but application ofNa fertilizer decreased the calcium (Ca) concentration in the expanding leaves due toreduced Ca uptake and Ca translocation from root to shoot, which was investigated innutrient solution experiments with Na and K treatments.Despite many fruitful findings from the earlier studies on Na nutrition of plants, inpractical agriculture Na is not used as a nutrient. We conclude that Na may substitute K toa large extent in sugar beet nutrition without affecting the plant growth and beet quality,and soils with higher K-fixing capacity and illite and/or vermiculite clay minerals are morefavorable for this substitution.Verknüpfung zu Publikationen oder weiteren Datensätzen
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Giessen : VVB Laufersweiler 2008