INFLUENCES OF PHOSPHORUS DEFICIENCY ON THE UPTAKE OF NITROGEN, POTASSIUM, CALCIUM, MAGNESIUM, SULFUR, AND ZINC IN LOWLAND RICE VARIETIES

Abstract

A field experiment was conducted to study the effect of phosphorus (P) deficiency on the mineral nutrition of five modern, high-yielding rice varieties, Purbachi, BR1, BR3, BR14, and BRRIDHAN29. The available P in the soils of different plots of the experimental field varied from 2.8 to 16.4 mg kg⁻¹. Such a wide range of available P in the different plots resulted from differences in the amounts of P (0 to 480 kg ha⁻¹) applied over a period of 8 years during a previous long-term P fertilizer trial in the same field.

The relationship among the P, potassium (K), and magnesium (Mg) concentrations in rice straw and grain in a soil P deficiency situation were especially noteworthy. The K concentration in rice straw was negatively correlated with the P concentration (r = −0.42 to −0.60), but in the case of grain the coefficient of correlation between P and K concentration were positive (r = 0.60 to 0.74). There was a strong positive relationship between the P and Mg concentration in grain (r = 0.70 to 0.97). These results suggest that the P deficiency in soil does not only affect the P nutrition of rice, but may also affect the uptake of other nutrients, especially that of K and Mg. The concentration of P in rice straw or grain increased or decreased, obviously, with an increase or decrease in the available P level in soil. Of interest, however, was the observed effect of the P concentration on the concentrations of nitrogen (N), K, and Mg in rice straw and grain.

Acknowledgments