Abstract
ABSTRACT: Subirrigation applies water and nutrients to the bottom of pots without wetting leaves, improving water use and reducing disease spread compared to overhead irrigation systems. However, water levels applied within the benches are often higher than required to promote capillary action, applying more water than needed and wasting pumping energy. The present study was conducted to evaluate the effect of different water levels on plant growth of subirrigated salvia (Salvia splendens) 'Vista Red' in two substrates. Five water levels (0.75, 1.5, 3.0, 4.5, and 6.0 cm) and two substrates {pine bark: sphagnum peat moss and peat: perlite (both 75%: 25% v/v)} were tested, with four replications. Substrate moisture was monitored by capacitance-type sensors connected to a multiplexer and data logger. Volumetric water content (VWC) was higher in peat: perlite (0.34 to 0.75 m3/m3) than pine bark: sphagnum peat moss (0.21 to 0.60 m3/m3) at all water levels. Higher water levels increased VWC in both substrates. The leaf chlorophyll index was 4% lower at the 6.0 cm compared to the other treatments in peat: perlite (p<0.0001). Stomatal conductance decreased overtime; but increased with the increase in water levels in peat: perlite (p<0.0001). Different water levels had no effect on leaf area, net photosynthesis, number of branches and leaves, and shoot dry weight (p>0.05), an indication that the different water levels do not affect the plant growth. However, shoot plant height increased 13% in pine bark: sphagnum peat moss (p=0.0096) and 17% in peat: perlite (p=0.0335) as water levels increased. Water levels of 1.5 cm and higher can be recommended for pine bark: sphagnum peat moss or peat: perlite in subirrigation, applying water according to plant needs, optimizing plant growth and reducing the nutrient solution pumping costs compared to systems that apply higher water levels.
Highlights
Crescimento de sálvia ‘Vista Red’ em subirrigação com diferentes alturas de lâmina de água em dois substratos
The peaks in Volumetric water content (VWC) values for all treatments indicate daily irrigations, followed by gradual decreases caused by evapotranspiration
Higher water levels resulted in higher VWC in both substrates, which is in agreement with other studies using sensor-based subirrigation (Ferrarezi et al, 2014) and drip irrigation (Bayer et al, 2013), where higher thresholds to trigger irrigation resulted in higher VWC
Summary
Crescimento de sálvia ‘Vista Red’ em subirrigação com diferentes alturas de lâmina de água em dois substratos. Alturas de lâmina de água maiores que 1,5 cm podem ser recomendadas para casca de pinheiro: esfagno ou turfa: perlita em subirrigação, com aplicação de água de acordo com as necessidades das plantas para otimização do crescimento vegetal e redução dos custos de bombeamento de solução quando comparado com sistemas de irrigação que aplicam lâminas de água mais elevadas. Capacitance sensors were previously used in subirrigation by Ferrarezi et al (2015b) in hibiscus (Hibiscus acetosella) ‘Panama Red’ and by Ferrarezi et al (2014) in salvia ‘Vista Red’ using ebb-and-flow, and by Gent & McAvoy (2011) in zonal geranium (Pelargonium × hortorum) ‘Allure Red Passion’ using flood-floor In these studies, the authors used only a fixed water level, provided by a specific time to allow an adequate substrate VWC. As subirrigation provides a variation in VWC after irrigations, the proper water level to apply the target VWC needs to be studied to avoid water stress caused by the deficit or excess of substrate moisture
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