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

Abstract

Additional index words. automatic irrigation system, nursery crops, overhead irrigation, plantbased irrigation, substrate-based irrigation

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

“…This study showed that plant available water potential can be different in different substrates and it can extend beyond −10 kPa tension for some substrates. Other recent studies also reported a dynamic range of plant available water depending on substrate type, or plant species [13,27,28] and an extended range of plant available water potential [13,29]. Our results showed that species-specific plant available water and water buffering capacity determination in the greenhouse using plant gas exchange parameters are a more accurate approach than the laboratory-based tests that consider −10 kPa tension as the end range of water buffering capacity.…”

“…The models' r 2 are provided in the last column of the table. = a/(1 + exp (−(VWC − x 0 ) The sigmoidal relationship between VWC and plant gas exchange, specifically the maximum or near maximum gas exchange rate over a range of moisture levels, was consistent with that of 'Silver Dollar' hydrangea and hibiscus 'Cashmere Wind' grown in substrates containing pine bark, peat moss, and/or biochar [25,27,36]. Coir treatments supported a higher maximum predicted photosynthetic rate in comparison to the non-amended pine bark.…”

“…An increasing amount of literature suggests that irrigation set points can be determined through plant-based model development experiments and adopted as conservative irrigation systems for nursery production with minimal species-specific development [25,26] and some other woody crops [37]. Moreover, in previous studies plant physiology based irrigation models were developed in the greenhouse and then evaluated for a production cycle outdoors, which resulted in water savings compared to the traditional practice of irrigating 1.8 to 2.54 cm of water per day [24,27]. Model development could be conducted by consultants using those species that are grown in the greatest numbers and thus affect a disproportionate amount of water use.…”

“…Some studies report plant available water potential can vary by substrate and can extend beyond the established threshold of −10 kPa tension for some substrates. Recent studies report a dynamic range of plant available water in different substrates or crop species [13,27,28] and an extended range of plant available water potential [13,29]. The second objective was to evaluate two methods for determining plant available water (plant gas exchange parameters and substrate physical properties) and establish which of the two was better suited as a basis for irrigation scheduling.…”

Stratified substrates enhance water storage and distribution between irrigation events

“…As shown in Figure 5, the dramatic change in moisture content is noticeable in traditional systems under standard irrigation practices. The irrigation schedule implemented in container production (N. Jahromi et al., 2018) paired with the manipulation of the hydraulic characteristics of a substrate profile (Fields, Owen, & Altland, 2021) can have a strong effect on substrate moisture status within substrate systems (Criscione et al., 2021). Cyclic irrigation applications can increase (less negative) Ψ upper values by continuously replacing water lost through either surface evaporation or downward through gravitational pull (Figure 5B).…”