Effect of potassium application on celery growth and cation uptake under different calcium and magnesium levels in substrate culture

The effect of potassium (K) on celery (Apium graveolens L.) growth and cation uptake was studied under different calcium (Ca) and magnesium (Mg) levels in substrate culture in the greenhouse. Shoot and root fresh and dry weight and leaf area increased with increasing K application up to 8 mmol l−1. High level of Ca and Mg (16 mmol l−1) significantly inhibited celery growth compared to lower levels (4 and 8 mmol l−1). In this study, K concentration in celery increased with increasing K application up to 8 mmol l−1, but did not change significantly with further increases in K application. In contrast to K, the opposite trends were found for Na, Ca and Mg concentrations in celery. The order of K concentration in celery root, stalk and leaf was: stalk > root > leaf and for Ca was: leaf > stalk > root. Mg concentration in celery root and leaf was high when compared with stalk. In addition, 8 and 16 mmol l−1 of Ca and Mg levels increased celery cation uptake as compared with 4 mmol l−1 of Ca and Mg level. This study suggested that 4-8 mmol l−1 K applications under the condition of 8 mmol l−1 of Ca and Mg level were appropriate for the improvement of celery growth and nutrient uptake