Water and nutrient uptake of rose growing on two inert media

The experiment was carried out in Naples (40° 51’ N) from April 1997 to April 1998. Water consumption and nutrients uptake of greenhouse roses grown in an open soilless system were investigated. Two different inert media were compared: perlite and lapillus, a volcanic rock. Rose plants (cv Dallas) were grown in linear plastic containers covered with PE film. The concentrations of the nutrients in the solution were (in mmol L-1) 11 NO3-, 1.1 H2PO4-, 4 K+, 5 Ca2+, 1.5 Mg 2+, 2.5 SO42- and 140 mmol L-1 Fe3+ plus microelements. The EC and the pH were kept about 2.0 dS m-1 and 6.3 respectively. Water holding capacity (in vol.) was 50% in perlite and 16% in lapillus while the saturated hydraulic conductivity was 100 times higher in lapillus than perlite. Nutrients and water uptake changed during the growing period with no significant differences between the two substrates. The results showed a consistent decrease in water consumption arising from the highest value in July 1997 (4.4 mm day-1) to the lowest one in February 1998 (1 mm day-1). Mean total water consumption was 10880 m3 ha-1 vs. 19500 m3 ha-1 of nutrient solution supplied. The mean leachate was 43% in volume of the supplied nutrient solution and the total loss of N in the drainage water was 2000 kg ha-1 or about 60% of the supplied amount. The crop coefficient (Kc), defined as the ratio between actual and potential evapotranspiration, varied between 1.2 (December 1997) and a 0.4 (February 1998). The mean ratio N:P:K obtained by analysing rose leaves was 1:0.08:0.63 with no difference between the substrates.