Flood Irrigation of Container-grown Euonymus and Thuja as Affected by Fertilizer Rate and Substrate

Abstract

Abstract Euonymus fortunei [(Turcz.) Hand.-Mazz.] ‘Emerald Gaiety’ and Thuja occidentalis L. ‘Little Giant’ were grown outdoors in #1 (3 liter) containers for one season on waterproof, crushed stone beds flooded and drained from below the stone. Plants were grown in a bark substrate (2/3 pine bark:1/3 sphagnum peat) or a peat substrate (1/3 pine bark:2/3 sphagnum peat) with either a high or medium rate of incorporated, controlled release fertilizer [17N–2.6P–10K (Sierra 17–6–12)] [6.0 or 4.0 kg/m3 (l0.0 or 6.7 lbs/yd3)]. For both species, the high fertilizer rate resulted in less top dry weight, and higher substrate electrical conductivity (EC) and NO3-N. Foliar N levels were also higher with the higher fertilizer rate. Compared with bark, the peat substrate resulted in less top dry weight of Thuja (not Euonymus) and higher substrate EC, NO3-N and water retention, and foliar N levels. Substrate EC levels in the upper one-third [5 cm (2 in)] of the container were nearly twice those in the lower two-thirds [10 cm (4 in)], reaching 7.1 dS/m with the high fertilizer rate in peat. In comparison to plants under overhead irrigation (high fertilizer rate only), flooded plants grew as much as (Euonymus) or more (Thuja) in the bark substrate but both species grew less in the peat. Substrate EC and NO3-N with flood were either similar or lower in bark, but similar or higher in peat compared to overhead. The amount of roots and their distribution appeared similar for both types of irrigation.