Evaluation of Temperature Effects on K Uptake by Corn

Changes in both plant uptake and soil supply parameters with temperature may restrict K uptake from cold soils. The objective of this research was to determine the effect of temperature on each of the soil and plant parameters used in a model simulating K uptake by corn (Zea mays L.). Then, using these measurements, to compare predicted by the simulation model with observed uptake. The parameters used in the simulation model were for the plant: root length at the start of the experiment; root growth rate; mean root radius; K influx as affected by K concentration outside the root; water influx; and for the soil: initial K concentration in soil solution; buffer power of K on the solid phase for K in solution; and the effective diffusion coefficient for K in the soil. The soil parameters were measured after equilibration of soils at 15 and 29 C in the laboratory. Where no additional K was added to the soil, soil solution K at 15 C was one-half, buffer power was 1.7 and the effective diffusion coefficient was 0.4 of that at 29 C. The plant growth experiments were conducted in a controlled climate with an air temperature of 29 C and root temperatures of 15 C and 29 C. The K influx characteristics of corn roots as affected by root temperature were determined in solution culture experiments. Potassium influx at 15 C was one-half that at 29 C. Root length increase while plants were subjected to root temperature differentials for 6 days (age 10 to 16 days) was 8 tunes greater at 29 C than at 15 C. These two factors resulted in a shoot K of 8.1% at 29 C and 3.7% at 15 C. Root growth rate, root radius, and mean water influx were measured for plants growing in soil at 15 and 29 C. Potassium uptake predicted by the simulation model was correlated (R² = 0.98) with observed K uptake. A sensitivity analysis predicted the effects on K uptake of changes in the parameters used in the model that were due to temperature changes.