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This article in AJ

  1. Vol. 77 No. 4, p. 524-527
     
    Received: Aug 22, 1984
    Published: July, 1985


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doi:10.2134/agronj1985.00021962007700040005x

Soil Moisture Effect on Potassium Uptake by Corn1

  1. A. D. Mackay and
  2. S. A. Barber2

Abstract

Abstract

Soil moisture influences K uptake by corn (Zea mays L.) by affecting root growth rate and the rate of K diffusion in soil. The extent each affects K uptake has not been resolved. The objective of this study was to determine the effect of soil moisture on each of the parameters of a mechanistic-mathematical model that simulates K uptake by corn. Corn was grown for 7, 14, and 21 days at three volumetric soil moisture levels, 0.22 (M0), 0.27 (M1), and 0.32 (M2), the water held at potentials of −7.5, −33, and −170 kPa, respectively, with three soils (S0 and S1, Raub, fine-silty, mixed, mesic Aquic Argiudolls, and S2, Chalmers, fine-silty, mixed, mesic Typic Haplaquolls, silt loams; S0 was low in K, S1 and S2 were medium in K), in 3-L pots in a controlled-climate chamber. Root growth and K uptake by corn were measured. Raising soil moisture from M0 to M1 increased shoot K uptake by 81, 70, and 68%, with the S0,, S1, and S2 soils, respectively. Raising soil moisture further, from M1 to M2 resulted in a further increase of 13% in K uptake by corn with the S0 soil but small decreases of 13 and 8%, with the S1 and S2 soils, respectively. Raising moisture from M0 to M1 also increased root growth, however a further increase to M2 decreased root growth. There was a relation between root surface area and K uptake, but this varied with soil. The relation between mean K influx and K uptake (r = 0.85**, significant at the 0.01 level), however, was independent of soil. Soil moisture did not significantly (P<0.05) affect K influx. Raising soil moisture from M0 to M2, increased the effective diffusion coefficient, De, for K an average of 2.1 times across the three soils. When all the data were used in the simulation model, calculated K uptake (y) in mmol pot−1 agreed with observed K uptake (x) by corn (y = 0.9x - 0.08; r = 0.95**), indicating that the model is a useful method for studying the effect of soil moisture on each of the mechanisms involved in K uptake by corn.

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