Abstract
Water resources can be used more efficiently by including sustainable substrate components like coir that increase water-holding capacity. The first objective of this study was to evaluate the impact of coir amendment rate on plant available water and plant gas exchange, with the goal of optimizing substrate available water and determining the optimum coir amendment rate in a greenhouse environment. The second objective was to establish the optimum method of determining plant available water using either plant gas exchange parameters or substrate physical properties. Greenhouse experiments were conducted with Hydrangea paniculata ‘Jane’ (Little Lime® hardy hydrangea) potted with one of five different coir rates (0%, 10%, 25%, 40% and 65%) mixed with pine bark on a volume basis. Plant gas exchange parameters and substrate water content were measured daily over a range of increasingly drier substrate moisture contents. Actual photosynthetic rates increased with increasing coir amendment rate and were highest with 65% coir amendment. Amending pine bark with coir increased the water storage capacity, plant available water, and plant gas exchange parameters. Results suggest that 65% coir amendment rate was the optimum amendment rate among those tested in a greenhouse environment and plant photosynthetic rate was the better method of determining plant available water.
Highlights
Agricultural irrigation is a major water consumer, responsible for about 70% of worldwide consumptive use [1] and about 30 percent of total withdrawals in the US [2]
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
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
Summary
Agricultural irrigation is a major water consumer, responsible for about 70% of worldwide consumptive use [1] and about 30 percent of total withdrawals in the US [2]. Nursery production is an intensive form of agriculture that uses relatively large amounts of water, nutrients, and pesticides [3,4,5]. A typical container nursery in the USA consumes over 180 m3 water per hectare per day during the growing season [6]. Inefficient use of irrigation can exacerbate the present water shortages, and is likely to increase during drought, which results in imposing restrictions on irrigation [7]. Developing management practices that make more efficient use of water is important for economically and environmentally viable production systems [11]. Water resources can be used more efficiently without the need for additional infrastructure by including more sustainable substrate components [12], including those that increase water-holding capacity or more efficiently deliver the water to the plant [13]
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