Influences of phosphorus deficiency on the uptake of nitrogen, potassium, calcium, magnesium, sulfur, and zinc in lowland rice varieties

A field experiment was conducted to study the effect of phosphorus (P) deficiency on the mineral nutrition of five modem, high-yielding rice varieties, Purbachi, BR1, BR3, BR14, and BRRIDHANT29. 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.