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Soil Temperature Effects on Root Growth and Phosphorus Uptake by Corn¹

ABSTRACT

Temperature affects each of the mechanisms involved in P uptake by corn. The extent to which each reduces P uptake, however, has not been resolved. The objective of this study was to determine the effect of temperature on each of the parameters used in a mechanistic mathematical model that predicts P uptake and then to use the model in a sensitivity analysis to evaluate the temperature dependency of parameters critical for predicting P uptake by corn. The effect of soil temperature, 18 and 25°C, and soil P status on root growth and P uptake by corn (Zea mays L.) was investigated in a series of pot experiments in a controlled climate chamber. Total yield of corn was 4- to 6.4-fold, root growth 2.6- to 5.1-fold, and P uptake 2- to 4-fold greater at 25°C than at 18°C. Increasing air temperature to 25°C while holding soil temperature at 18°C resulted in a 2.7-fold increase in root growth and a 2.2-fold increase in P uptake. Predicted P uptake calculated with a mechanistic mathematical model by corn grown for 8, 15, and 21 d agreed with observed P uptake at both 18°C (y = 0.97x + 3.64, r = 0.99**) and 25°C (y = 1.07 x – 1.86, r = 0.99**). In the sensitivity analysis the parameters used to calculate P uptake at 18°C were changed individually to those measured at 25°C and then P uptake was again predicted. Rate of root growth, which increased 4.97-fold when temperature increased from 18 to 25°C, had the most pronounced effect on calculated P uptake, indicating that this was the primary reason low temperature reduced P uptake by corn. The parameters describing the movement of P to the root surface and P uptake at the root surface appear to play only a minor role in causing reduced P uptake by corn at low temperature.

¹ Journal Paper no. 9740. Purdue Univ. Agric. Exp. Stn., W. Lafayette, IN 47907. Contribution from the Dep. of Agron. This paper was supported in part by a grant from Tennessee Valley Authority.

² Post-Doctoral Research Associate and Professor of Agronomy, Purdue Univ., respectively.

Received for publication December 23, 1983. Accepted for publication March 6, 1984.