Growth and cation absorption of some fruit‐vegetable crops grown on rockwool as affected by different cation ratios in the nutrient solution

In a series of experiments, cucumber, eggplant and sweet pepper were grown in rockwool with nutrient solutions of different ratios of potassium (K), calcium (Ca) and magnesium (Mg). The ratios between the anions in the nutrient solutions compared were the same. In addition to yield, the concentrations of cations in the root environment and in different plant tissues were determined. The results show that the yield for eggplant fruits were strongly reduced by a low Mg level, while the yield of cucumbers seemed to be somewhat reduced by a low Ca supply. Sweet pepper yields were not affected among the cation ratios compared. Relationships between cation contents in the root environment and cation contents in plant tissues were established. The correlation coefficients for these relationships were very high. The equations calculated for the various cations show remarkable differences. Regression coefficients and intercepts strongly depend on crop and plant part sampled. For Mg, it could be established that Ca strongly affected the uptake of Mg.