Growth Response, Mineral Nutrition, and Water Utilization of Container-grown Woody Ornamentals Grown in Biochar-amended Pine Bark

Abstract

<jats:p>Container-grown nursery crops generally require daily irrigation applications and potentially more frequent applications during the hottest part of the growing season. Developing management practices that make more efficient use of irrigation water is important for improving the sustainability of nursery crop production. Biochar, a byproduct of pyrolysis, can potentially increase the water-holding capacity and reduce water and nutrient leaching. In addition, the development of sensor-based irrigation technologies has made monitoring substrate moisture a practical tool for irrigation management in the nursery industry. The objective of this research was to determine the effect of switchgrass biochar on water and nutrient-holding capacity and release in container substrates of <jats:italic>Buxus sempervirens</jats:italic> L. × <jats:italic>Buxus microphylla</jats:italic> (‘Green Velvet’ boxwood) and <jats:italic>Hydrangea paniculata</jats:italic> (Pinky Winky<jats:sup>®</jats:sup> hardy hydrangea). Containers were filled with pine bark and amended with 0%, 10%, or 25% volume of biochar. Plants were irrigated when the volumetric water content (VWC) reached the water-buffering capacity set point of 0.25 cm<jats:sup>3</jats:sup>·cm<jats:sup>−3</jats:sup>. The sensor-based irrigation in combination with the low cost biochar substrate amendment increased substrate water-holding capacity and reduced irrigation requirements for the production of hydrangea, a high water use plant. Biochar application rate influenced irrigation frequency, which likely affected plant biomass for hydrangea, but boxwood dry weight was unaffected by biochar rate. Total irrigation applied was decreased by 32% in 10% biochar treatment without reducing hydrangea dry weight. However, in the 25% biochar treatment, total irrigation applied was reduced by 72%, whereas dry weight decreased by 50%. Biochar application reduced leaching volume and leaching fraction in both plants. Leachate analysis over the course of the 8-week experiment showed that the average mass of phosphate (PO<jats:sub>4</jats:sub>), potassium (K), and total carbon was greater in the leachate from containers that received 25% biochar compared with those receiving 0% or 10% biochar for both plant species. For hydrangea, mass of total nitrogen (TN) and nitrate (NO<jats:sub>3</jats:sub>) in leachate was not significantly affected by increasing the biochar rate. However, for boxwood, the mass of NO<jats:sub>3</jats:sub> and TN was greater in the 25% biochar treatment leachate, whereas the mass of ammonium (NH<jats:sub>4</jats:sub>) was unaffected. In hydrangea, total nutrients lost from the containers was lower in biochar-amended containers (both 10% and 25% biochar) because of receiving a lower total volume of water. Amendment with biochar also affected concentration of phosphorus (P) and K, with the highest concentration in both leaf tissue and substrate from the 25% biochar application rate.</jats:p>

Effects of Biochar on Container Substrate Properties and Growth of Plants—A Review

“…The biochars made from different feedstocks could have different physical and chemical properties, which should be taken into account when they are incorporated in containers. Sugarcane bagasse z 343 n n n 0.11 5.8 n n n n n n n n n n [48] Sugarcane bagasse z 343 n n n 0.11 6.1 n n n n n n n n n n [48] Switchgrass z 1000 n n n 0.10 10.8 3.5 n 1.3 79.0 1.20 6.60 n n n n [69] Wheat straw 600 n n n 0.31 10.0 1.0 n 1.0 79.3 n n n n n n [70] Wheat straw n n n n 0.24 9.5 2.5 n n n 0.003 0.10 0.002 0.004 0.0009 n [5] Note: Production temp: production temperature; CC: container capacity; AS: air space; TP: total porosity; BD: bulk density; EC: electrical conductivity; CEC: cation exchange capacity. Pyrolysis was the biochar production method, unless indicated otherwise.…”

Post-transplant Water Utilization of Zinnia Seedlings Grown in Humectant-amended Substrate Maintained at Two Moisture Thresholds1

“…While less likely to occur with liquid additives, incorporating solid amendments (e.g. biochar, manure, peat, or vermiculite) has been shown to alter substrate physical properties such as bulk density, air space and container capacity (Jacobs et al 2003, Jahromi et al 2018. Thus, any decision to utilize soil additives should take into account the potential impact of these amendments on the physical properties of an existing substrate.…”

“…Since humectants such as Hydretaint form strong hydrogen bonds between hydrophilic components of the humectant and water molecules within the substrate matrix, it is possible that these bonds could limit the availability of moisture for absorption by plant roots until, presumably, plant-water potential decreases (becomes more negative), resulting in a directional shift in the water potential gradient. In a study using biochar as a substrate amendment, Jahromi et al (2018) reported that the shoot dry weight of potted hydrangeas (Hydrangea paniculata Siebold) grown in 25% biochar-amended Plants grown from seed in plug trays for 4 weeks prior to transplanting into SP#4 (1L) marketable pots filled with soilless substrate. Transplants allowed to become established for 10 days before beginning the experiment.…”

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

“…Coir rates were selected to test a wide percentage range of substrate amendment. Including 10% and 25% coir enabled comparison with results from previous research with biochar [16]. Positive results from other research with 35% coir as a substrate amendment [13,31] supported including higher rates to begin to define the highest rate at which benefits would be derived and provide producers with recommendations.…”

“…In previous studies we used biochar as a substrate amendment and observed its positive effects on increasing water holding capacity, reduction of water and nutrient loss. Biochar amendment affects nutrient concentration and can act as a source of phosphorus and potassium depending on the feedstock type [16][17][18][19].…”