EFFECT OF SOLUTION NITROGEN CONCENTRATION ON YIELD, LEAF ELEMENT CONTENT, AND WATER AND NITROGEN USE EFFICIENCY OF THREE HYDROPONICALLY-GROWN ROCKET SALAD GENOTYPES

Abstract

Two species of rocket salad, Eruca vesicaria L. subsp. sativa Miller and Diplotaxis tenuifolia L. DC, were grown hydroponically in a growth chamber with two nitrogen levels (1 or 8 mM N) to evaluate nitrate accumulation and nitrogen use efficiency. One ecotype of Eruca and two of Diplotaxis were used. Nitrogen (N) increased leaf production and the contribution of leaves to the total dry mass production in E. vesicaria but not in D. tenuifolia, and emphasized leaf area differences between the two species. The two species also showed differences in the inorganic anions and N content. D. tenuifolia ecotypes accumulated more NO₃ than E. vesicaria (7.7 vs. 4.7 g kg⁻¹ fresh mass). By increasing N concentration in the nutrient solution, NO₃ content in leaves expressed on fresh mass basis increased in both species by 52%.

Nitrogen use efficiency was greater in E. vesicaria than in D. tenuifolia (19.0 vs. 18.0), and decreased with increasing nitrogen in the nutrient solution (19.0 vs. 17.6).

ACKNOWLEDGMENT

The University of Bari (60% 1997 fund allocation) funded the work within the Research Project “Nitrogen use efficiency and quality of leaf vegetables”.