Improving growth and quality of Hibiscus acetosella and Qardenia jasminides with efficient irrigation and fertilization for more sustainable container plant production
Bayer, Amanda Leigh
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Improving water and nutrient management is a focus of sustainable container plant production. Best management practices are commonly used and although effective, these methods do not take into account actual plant water needs. Irrigating in response to substrate volumetric water content applies only the water needed by the crop to replace what is lost to evapotranspiration and plant water use. Soil moisture sensor technology can allow for precise and efficient control of irrigation in response to substrate water content. To best utilize this technology an understanding of the effect of irrigation volume and water stress on plant growth is needed. The aim of this research was to understand how plant growth is affected by substrate water content and irrigation volume. Hibiscus acetosella and Gardenia jasminoides were irrigated using an automated irrigation systems set to maintain substrate volumetric water content above various thresholds in order to quantify plant growth and irrigation volume. Experiments were conducted in Watkinsville and Tifton, GA in order to assess differences due to environmental conditions. Growth of Hibiscus acetosella increased with increasing volumetric water content threshold, with plants above the 0.35 m3∙m-3 threshold of a salable size, which suggests that moderate irrigation volumes can be used in plant production. Growth of two Gardenia jasminoides cultivars responded similarly to volumetric water content threshold. Bud and bloom development was greater at the 0.40 m3∙m-3 threshold than the 0.50 m3∙m-3 threshold indicating that over-irrigation can impact bud and bloom development. Plant growth of Gardenia jasminoides was similar when grown with 50% and 100% of the standard bag rate of a controlled release fertilizer indicating that reduced fertilizer applications can be possible with more efficient irrigation. Efficient irrigation also reduced leachate volume. There were diurnal patterns of stem elongation of Hibiscus acetosella for both well-watered and water-stressed plants with elongation rates greatest after the onset of darkness. Further research with additional species will provide additional information in order to most effectively utilize sensor controlled irrigation and reduced fertilizer applications in a commercial plant production.