Evaluating a Physiological-based, On-demand Irrigation System for Container-grown Woody Plants with Different Water Requirements

Abstract

<jats:p>Two sensor-based irrigation scheduling systems were compared for water use and plant growth in container-grown Green Velvet boxwood (<jats:italic>Buxus sempervirens</jats:italic> L. × <jats:italic>B. microphylla</jats:italic> Siebold &amp; Zucc. var. <jats:italic>koreana</jats:italic> ‘Green Velvet’) and slender deutzia (<jats:italic>Deutzia gracilis</jats:italic> Siebold &amp; Zucc). These crops were chosen because they have different water requirements during production. The two sensor-based irrigation systems included a physiological-based on-demand (OD) irrigation system where the set point was derived from the relationship between substrate moisture and photosynthetic rate. The second system was a daily water use (DWU) method where the amount of water used by the crop was replaced each day. The objective of the study was to evaluate and compare water use and growth metrics using the OD and DWU irrigation scheduling regimes for two container-grown woody plants that differed in their water consumption. There were no differences in root and shoot biomass or growth index due to the irrigation schedule employed for either boxwood or deutzia. For boxwood plants, OD irrigation reduced water consumption by 35.5% and enhanced water use efficiency (WUE) by 54.5% compared with DWU. Total water use of deutzia in OD zones was reduced by 26.5% compared with DWU. DWU offers the labor scheduling advantage of irrigation occurring at a set time of day, and OD offers the advantage of watering as required, potentially reducing water stress as the season progresses and as the plant size and atmospheric demand increase.</jats:p>

Evaluating On-demand Irrigation Systems for Container-grown Woody Plants Grown in Biochar-amended Pine Bark

“…events, which may affect plant growth. The moisture deficit in traditional irrigation systems might approach or exceed the water buffering capacity, which results in little to no plant-available water (Nambuthiri et al, 2017). This appears to contradict the results of Warsaw et al (2009) somewhat, who found that even moderate moisture deficit had little to no effect on plant growth.…”

“…Nambuthiri et al (2017) reported that the moderate moisture deficit created by on-demand irrigation systems improved WUE by reducing the water use and leachate volume without a negative effect on plant growth. A plant-based irrigation schedule improved irrigation efficiency in Hibiscus rosa-sinensis 'Cashmere Wind', oakleaf hydrangea (Hydrangea quercifolia 'Alice'), and slender deutzia (Deutzia gracilis) (Fulcher et al, 2012;Hagen et al, 2014;Nambuthiri et al, 2017).…”

“…The substrate-based and conventional irrigation systems used the same amount of water, but the conventional irrigation system had a greater leachate volume. Both on-demand schedules may prevent the substrate from becoming hydrophobic by minimizing the length of time a substrate dries between irrigation events (Nambuthiri et al, 2017), reducing channeling of water and thus leachate volume and associated fertilizer leaching (Hoskins et al, 2014). The tendency of water to channel through the substrate increases when applied to the dry substrate (Hoskins et al, 2014).…”

“…The simplest method (hereafter called the substrate-based method) is to assume a range of plant-available water tensions, usually defined as -1 kPa and -10 kPa (Arguedas-Rodriguez, 2009), although this range can be extended beyond -10 kPa tension to achieve greater water savings (Fields et al, 2016). A more recently established method of predicting crop water use by plant physiological status (Cifre et al, 2005;Jones, 2004) can be based on the relationship between photosynthetic rate and substrate moisture content before the plant photosynthesis rate is reduced by water stress (Fulcher et al, 2012;Hagen et al, 2014;Nambuthiri et al, 2017). This method is hereafter referred to as the plant-based approach.…”

Optimizing Substrate Available Water and Coir Amendment Rate in Pine Bark Substrates

“…Photosynthetic rate has been successfully used as an irrigation-scheduling basis to improve crop water use efficiency [24][25][26]. Photosynthetic rate is related to stomatal conductance and both are impacted by as well as impact leaf water potential.…”