Aluminium sensitivity of two upland rice cultivars at various levels of nutrient supply

Two upland rice (Oryza sativa L.) cultivars with high (IR45) and low (BG35) aluminium (Al) sensitivity were selected to investigate the influence of Al on growth and uptake and distribution of macronutrients potassium (K), phosphorus (P), calcium (Ca), and magnesium (Mg)] when the plants were grown at various levels of nutrient supply. The plants were grown for 21 days with or without 140 μM Al at pH 4.1. Nutrients were supplied with 2.5, 5.0, 10, or 15% relative increase/day relative nutrient addition rate (RNR), according to a nutrient supply program. In this range of nutrient supply rates, the degree of Al sensitivity in the two rice cultivars was not markedly affected, except for root growth in BG35 that was more inhibited at low RNRs than at high RNRs. Regardless of nutrient supply rate, Al was mainly confined to the roots in both cultivars. However, the concentrations of Al in the shoots was consistently lower in BG35 than in IR45. Different Al sensitivity in BG35 and IR45 was associated with different influence on uptake and distribution of P and Ca. Uptake of Mg was drastically inhibited by Al at all nutrient supply levels in both cultivars. Uptake and distribution of K were not negatively affected by Al.