Nitrogen, phosphorus, and potassium influx kinetic parameters of three rice cultivars

Abstract

Information about the nutrient absorption properties of rice (Oryza sativa L.) roots can be used to predict nutrient uptake and to determine levels needed in the soil to supply nutrients rapidly enough to the root surface to minimize deficiencies. A study was conducted to measure the maximum influx (I_max), the respective Michaelis constants (K_m), and the minimum solution concentrations necessary for uptake (C_min) of nitrogen (NH4⁺), phosphorus (PO4³‐), and potassium (K⁺) by three rice cultivars (Katy, Lemont, and Mars). Single plants of a given cultivar were transplanted into a nutrient solution containing a low concentration of a given element. The solution was sampled continuously for 10 to 15 h, following which roots were harvested and root surface areas determined. The three influx parameters for each cultivar and element were calculated from the individual nutrient depletion curves. The only effect of cultivar was found for the Imax of K⁺. Potassium Imax for Katy was 42% lower than for Lemont, and the Imax for Mars was intermediate. Average values of Imax for NH⁴⁺, PO₄ ^3‐ and K⁺ were 475.1, 12.4, and 22.2 nmol/m²/s, respectively, and for Km were 61.8, 3.4, and 6.2 μmol/L, respectively. Minimum concentrations needed for uptake by rice for NH⁴⁺, PO₄ ³‐, and K⁺ were 3.1,1.4, and 2.3 μmol/L, respectively.

Notes

Deparment of Agronomy, University of Arkansas, Fayetteville, Arkansas 72701

Agricultural Statistics Laboratory, University of Arkansas, Fayetteville, AR 72701

Corresponding author. Published with permission of the Director of the Arkansas Agricultural Experiment Station.