The impact of substrate and irrigation interval on the post-transplant root growth of container-grown zinnia and tomato1

Abstract

Substrate type and irrigation interval were studied to determine their impact on the post-transplant root growth of ‘Thumbelina' zinnia (Zinnis elegans Jacq.) and ‘Celebrity Hybrid' tomato (Lycopersicon esculentum Mill.). Seeds of both species were planted in 80 cm3 (2.7 fl oz) plug cells containing either Metromix 360™ (MM360) or Ball Professional Growing Mix™ (BPGM) and, following germination, the seedlings were transplanted into 450 cm3 (27.5 in3) plastic pots containing the same substrate. Evapotranspiration (ETO) was measured gravimetrically each day and the water lost via ETO added back to the substrate at intervals of 24, 48 or 96hr. For zinnia, root growth was consistently better for seedlings grown in BPGM, a substrate with greater water holding capacity and air-filled porosity. For plants grown in BPGM and irrigated every 48hr, root dry weight was significantly greater than it was for any of the remaining treatments. For tomato, root growth was greater for seedlings grown in BPGM and for transplants irrigated at 96 hr intervals; but, unlike zinnia, no significant interactions between substrate type and irrigation interval were observed. The results of this study show that root growth of plug-grown transplants can be improved by selecting a substrate with high porosity that allows for optimum oxygen and water exchange, and by extending the irrigation cycle to 48 hr (zinnia) or 96 hr (tomato). Index words: irrigation scheduling, moisture stress, plant establishment, soilless growing media, transplant production Species used in this study: ‘Thumbelina' zinnia (Zinnia elegans Jacq.); ‘Celebrity Hybrid' (Lycopersicon esculentum Mill.).

Environmental and Cultivation Factors Affect the Morphology, Architecture and Performance of Root Systems in Soilless Grown Plants

“…or 96 h for tomatoes (Lycopersicon esculentum Mill.) showed significantly higher root parameters than similar transplants watered daily [53]. Similarly, Ismail and Ozawa [54] found that a 3-day irrigation interval showed a remarkably higher root development for chili pepper than 1 or 5 d treatments.…”

“…The crosstalk between different nutrient signals and the benefits of RSA responses in a particular condition are yet to be characterized [43]. Primary root growth inhibition, increase in lateral roots and root hairs Various crops Various production system Limited P supply [39,41,46] Increase in vertical, deep roots Various crops Various production systems Limited N supply [40,43,47] Increased root dry weight, specific root length, root tissue density, and root length density due to increased irrigation intervals Tomato, Zinnia 450 mL plastic pots containing either Metromix 360 (MM360) or Ball Professional Growing Mix (BPGM) 24-h, 48-h, and 96-h irrigation intervals [53] Chili pepper 31 cm × 15 cm × 60 cm container filled with sandy-loamy soil 1-, 3-and 5-day irrigation intervals [54] When the growing system enables maintaining a constant concentration of each nutrient at the root surface, as is the case of NFT, DFT, and aeroponics, the ability of the restricted root system to meet plant requirements is not a limiting factor [12]. This is because frequent fertigation might improve the uptake of nutrients through the continuous replenishment of nutrients in the depletion zone at the vicinity of the root interface and enhance the transport of dissolved nutrients by mass flow [55].…”

“…Wood fiber substrate [66] Chili pepper 31 × 15 × 60 cm container filled with sandy-loamy soil 1-, 3-, and 5-day irrigation intervals [54] The irrigation method, rate, timing, and interval affect root initiation, elongation, branching, development, and dry-matter partitioning between roots and shoots [67]. Roberts et al [53] reported that plug-cell transplants irrigated at intervals of 48 h for zinnia (Zinnia elegans Jacq.) or 96 h for tomatoes (Lycopersicon esculentum Mill.)…”