Potassium and Nitrogen Distribution Pattern and Growth of Flue-Cured Tobacco Seedlings Influenced by Nitrogen Form and Calcium Carbonate in Hydroponic Culture

Abstract

ABSTRACT The influences of nitrogen form (NH4 +, NO3 −, and NH4NO3) with or without CaCO3 on the growth and potassium (K) and nitrogen (N) uptake and partitioning of flue-cured tobacco plants (Nicotiana tabacum L. cv. ‘K326’) were examined under the controlled conditions of nutrient-solution culture. Tobacco seedlings with four true leaves were grown in mixed substrate before being transplanted and grown in a pre-culture solution until the six-true-leaf stage. The following treatments were applied: NH4 +-, NO3 −-, and NH4NO3 alone, and each of these in combination with CaCO3. Seventeen days later, the plants were harvested. The results showed that NH4 + as the only N source resulted in lower dry weight of both leaves and roots compared with other N forms, including NO3 − and NH4NO3, without obvious ammonia toxicity in leaves. The CaCO3 addition was beneficial in ameliorating the growth suppression found in NH4 +-only plants, but the same effects of addition were not found in NO3 −-only plants. Sole NH4 + nutrition led to the lowest K concentration and content in leaves and roots, while sole NO3 −-only plants had the highest. Added CaCO3 also significantly improved the K concentration and content in NH4 +-only plants. However, NH4 + nutrition resulted in more K translocated to leaves than did NO3 − supply. Nitrogen concentration and content were only weakly affected by N form. Although NH4 +-only plants had the lowest N concentration and content in plants, there was no difference in N concentration in top leaves and roots between NH4 + and NO3 −-plants. Added CaCO3 also improved the N concentration in NH4 +-only plants. In contrast to its effect on K partitioning, the NH4 +-only treatment the lowest N concentration in leaves, while no differences in N partitioning were observed under other treatments. These results suggest that long-term use of 100% NH4 + in the nutrient solution reduces dry-matter accumulation and K uptake in tobacco plants and increases K accumulation in leaves. Added CaCO3 could reduced the suppression induced by 100% NH4 + to a certain extent.