Water Scarcity Footprint Analysis of Container-Grown Plants in a Model Research Nursery as Affected by Irrigation and Fertilization Treatments

Water scarcity footprint (WSF) was determined for irrigation experiments in 2017 and 2018 for container-grown plants in a specially designed research nursery in Michigan, USA. The system design allowed for the capture of irrigation water running off a fabric surface of a nursery bed and irrigation water that passed through the fabric surface and moved through a bed of sand under the fabric. The volume of irrigation water applied (IWA) from a groundwater source and the volume of water that would be necessary to dilute (WD) water leaving the system to tap water standards for NO3- and PO43- of 10 mg L-1 and 0.05 mg L-1, respectively, were determined. The sum of IWA and WD would be the consumptive water use (CWU) of each treatment. WSF was calculated by weighting these component volumes per plant grown in a 10.2 L container using the consumption-to-availability scarcity index for this river basin. The WSF of water requirements for dilution (WSFwd) for plants in 2017 (20 May to 25 September) were calculated as 150, 37, and 34 L per plant for control plants, those receiving 2 L per day, and those returned to container capacity daily, respectively. In 2018 (11 June to 12 October), WSF of irrigation water applied (WSFiwa) for control plants, those receiving daily water use replacement (DWU), and those returned to container capacity daily were calculated to be 116, 61, and 28 L. Control plants received 19 mm of irrigation daily through overhead sprinklers in both experiments. In almost all cases, the PO43- dilution requirements set the dilution coefficients for WSFwd calculations. The irrigation control treatment resulted in higher WSFwd than irrigation treatments through spray stakes providing 2 L per container per day, irrigation returning the substrate water content to container capacity daily, or daily irrigation based on DWU. Fertilizer treatments and substrate composition treatments across irrigation treatments had only a minor impact on WSF.