268 Nursery Irrigation Effects on Postplanting Root Dynamics of Limonium cossonianum O. Kuntze in Semi-arid Conditions

Abstract

A study was conducted with Limonium cossonianum O. Kuntze to analyze the influence of irrigation regime in nursery on the dynamics of root development after being transplanted with minimum management conditions. Plants were potgrown in a greenhouse. Each plant was potted into 625-mL plastic pot filled with a 1 silica sand medium: 1 peat mixture (v/v) amended with osmocote plus (3.7 g•kg-1 substrate). Drip irrigation was used with a 2-L•h-1 emitter per plant. Two irrigation treatments were used: T3, plants watered 6 days a week at the water-holding capacity (leaching 20% of the applied water) and T1, plants watered twice a week, receiving an amount of water at 30% of T3 plants troughout the nursery period (45 days). After nursery period, plants were transplanted in the open air at the southeast Mediterranean coast of Spain (37°47′N, 0°′54′W), and just one establishment irrigation was applied (50 mm). There were three replications. Plant root and top growth were measured weekly for 13 months. For the root dynamics study, minirhizotrons were used. Acrylic tubes, 2 m long and 80 mm in outside diameter, were placed at a inclination of 24°, reaching a total depth of 160 cm. The evolution of the root length density (RLD) was measured by seven 23-cm-deep soil layers. Results indicate that those plants that were less watered in nursery showed a greater RLD for the whole soil profile. Plants root growth for the top 46 cm of soil were not significantly affected by irrigation treatments; between 46 and 115 cm deep, T1 plants showed greater RLD than T3 (average values of 0.6 vs. 0.3 cm•cm-3); and under 115-cm deep (where root growth was more limited), there were not significant differences. For the first 6 months, a important plant top growth was observed, there being no significant differences among irrigation treatments. Research suported by CICYT grant AGF-96-1136-C02-02.