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An Evaluation of the Mechanisms Governing the Supply of Ca, Mg, K, and Na to Soybean Roots (Glycine max)
Author(s) -
Oliver S.,
Barber S. A.
Publication year - 1966
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1966.03615995003000010029x
Subject(s) - interception , transpiration , chemistry , leaching (pedology) , nutrient , volumetric flow rate , saturation (graph theory) , mass flow , soil science , soil water , environmental science , botany , mathematics , physics , photosynthesis , biology , ecology , combinatorics , biochemistry , organic chemistry , quantum mechanics
Three mechanisms, root interception, mass‐flow, and diffusion, govern the rate of supply of nutrients from the soil mass to the plant root. Two experiments were conducted to evaluate methods developed for calculating the supply of ions to the root by mass‐flow and by root interception. Root interception values were calculated by assuming that all the exchangeable and soluble ions were in the pore space and that the roots intercepted an amount in proportion to their volume. Mass‐flow was calculated by multiplying the amount of water uptake of the plant by the concentration of ions in this water as determined from analysis of a saturation extract. Contributions of mass‐flow were varied by creating three rates of transpiration. The results indicated that mass‐flow was significant for supplying Ca and Mg but was of little importance for Na and K in the soil used. Increases in mass‐flow of Ca and Mg were highly correlated with increases in the uptake of Ca and Mg by the plant. In a second experiment, root interception of Ca and Mg was varied by using soil‐sand mixtures varying from 100% soil to 20% soil and 80% sand. Mass‐flow was minimized by leaching the soil before use. The results indicated that the calculated Ca uptake by root interception gave a reasonably close approximation to uptake of Ca minus mass‐flow Ca.