Plant and Soil

, Volume 77, Issue 2–3, pp 347–365 | Cite as

Macro nutrient cation uptake by plants

II. Effects of plant species, nitrogen concentration in the plant, cation concentration, activity and activity ratio in soil solution
  • N. E. Nielsen
  • E. M. Hansen


In pot experiments with barley, mustard, leek, lettuce and spinach, and in a field experiment with 30 cultivars of barley uptakes of K, Mg, Ca, Na and N were studied at varying concentrations and activities of these cations in the soil solution.

The sum of macro cations (K, Mg, Ca, Na) in meq per 100 g aerial plant parts were independent of the chemical composition of the soil solution, but dependent on plant species and on the N concentration in the plant.

The ratios\((\bar I_{Mg} /\bar I_{Ca} and \bar In_K /2(\bar In_{Ca} + \bar In_{Mg} ))\) of mean net inflows of Mg, Ca and K into plants and corresponding cation activity ratios (aMg/aCa and\(a_K /\sqrt {a_{Ca} + a_{Mg} } \)) in the soil solution were linearly related and highly correlated under conditions in which growth rate and/or rate of incorporation into new tissues constituted the rate determining step of cation uptake. Consequently, mean net inflows of K, Mg and Ca were independent of ion concentration and ion activity of K, Mg or Ca in the soil solution under the conditions of constant activity ratio.

The results agree with the concept that plants have a finite cation uptake capacity, and that plants are in a equilibrium-like state with the activities of K, Mg, and Ca ions in the soil solution. The results indicate that both ratios and content of exchangeable cations should be considered in our evaluation of soil test data.

Key words

Barley Ca Cation activity Cation activity ratio Cation concentration Ion uptake Mg Mustard Leek Lettuce Soil solution Spinach Uptake capacity Uptake ratio Net inflow 


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Copyright information

© Martinus Nijhoff/Dr W. Junk Publishers 1984

Authors and Affiliations

  • N. E. Nielsen
    • 1
  • E. M. Hansen
    • 1
  1. 1.Department of Soil Fertility and Plant NutritionThe Royal Veterinary and Agricultural UniversityCopenhagenDenmark

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