Ornamental nurseries produce a large number of plants in a concentrated area, and aesthetics are a key component of the product. To produce crops in this manner, high inputs of water, nutrients, and pesticides are typically used. Container nursery production further increases the inputs, especially water, because container substrates are designed to quickly drain, and the most effective method of irrigating large numbers of plants in containers (up to a certain size) is the use of overhead irrigation. Because irrigation and pesticides are broadcast over the crop, and because the crop is limited to the container, a large proportion of water or pesticides may land on nontarget areas, creating runoff contaminant issues. Water is the primary means of pesticide movement in nursery production. This review discusses water and pesticide dynamics and management strategies to conserve water and reduce pesticide and water movement during container nursery production.
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 NO 3 − and PO 4 3 − 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 PO 4 3 − 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.
Short-cycle horticulture crops often rely on fertigation to provide immediately available nutrients. This practice poses an environmental threat when nutrients, particularly phosphorus, leach from containers and enter waterways. One method that could be used to reduce the loss of phosphorus and other key anions from horticultural crops is incorporating activated aluminum into container substrates. This study investigates the incorporation of three rates of activated aluminum into a pine bark substrate, and the effects this amendment may have on the container leachate nutrient content and the growth of a popular short-cycle crop (Tagetes patula, French marigold). The addition of activated aluminum reduced the cumulative mass of phosphorus in container leachate by 69–96% compared to a standard pine bark substrate. The growth index and subjective plant quality scores of Tagetes were equivalent between the activated aluminum-amended substrates and pine bark only substrates, in all cases, producing a salable, quality crop. This study demonstrates that incorporating activated aluminum into container substrates is an effective way to reduce phosphorus loss to the environment without sacrificing crop quality.
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