Preliminary Norms for DRIS to Fertigate Ornamental Shrubs

ABSTRACT

Preliminary norms for foliar tissue were developed for laurustine (Viburnum tinus L.), tobir (Pittosporum tobira Thumb.) and strawberry tree (Arbutus unedo L.) for its use in the diagnosis and recommendation integrated system (DRIS). These norms were generated from high quality plants grown in hydroponic cultures. The values were those of foliar tissues from two growing assays where the total (N) and (NO₃ ^?/NH₄ ⁺) ratio were optimized. These norms were applied to perform DRIS in plants grown in a mix of white peat and vermiculite (75:25 v:v). Nutrient reference levels obtained from hydroponic cultures were appropriate to be used as DRIS norms for these species, because DRIS indexes reflected the nutritive status of these species grown in a fertigated system. These results suggest the need to broaden the range of reference values to include the fertigation reference levels. DRIS detects the nutrient limitations as a consequence of the nutrient imbalance caused by the pH and nutrient concentration in the substrate solution. Therefore, DRIS is an adequate method of diagnosis and can be used to adjust the nutrient solution composition and to improve the nutritional status for these species.