Irrigation return flow and nutrient movement mitigation by irrigation method for container plant production

Authors: ABDI, DAMON - Michigan State University; Owen Jr, James - Jim; BRINDLEY, J - Virginia Tech; BIRNBAUM, ANNA - University Of Georgia; CREGG, BERT - Michigan State University; FERNANDEZ, R - Michigan State University

Submitted to: Irrigation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2021
Publication Date: 3/23/2021
Citation: Abdi, D.E., Owen Jr, J.S., Brindley, J.C., Birnbaum, A., Cregg, B.M., Fernandez, R.T. 2021. Irrigation return flow and nutrient movement mitigation by irrigation method for container plant production. Irrigation Science. 39:567-585. https://doi.org/10.1007/s00271-021-00727-1.
DOI: https://doi.org/10.1007/s00271-021-00727-1

Interpretive Summary: Nursery growers prioritize producing a quality crop, which may come at the expense of increased water and fertilizer use. However, more efficient irrigation application methods can potentially produce an equivalent crop to conventional methods using overhead irrigation. The use of applying water directly to the containerized crop can reduce water use. Additionally, crop quality (particularly compactness) may be improved by using spray stake irrigation. In Michigan, Spray stakes reduced irrigation by 76-80% compared to the overhead control, and reduced the generation of both surface and subsurface irrigation return flow, mitigating the movement of both nitrogen and phosphorus. Beyond water savings, the reduced volumes of irrigation return flow may facilitate more efficient methods of capturing and treating irrigation return flow, prior to release to the surrounding environment resulting in a need for less dedicated infrastructure for retention ponds and/or contaminant remediation systems.

Technical Abstract: The production of nursery crops demands substantial irrigation, with overhead irrigation the most common method of application; however, this method is inefficient with respect to water used and the precision with which it is applied, resulting in the generation of irrigation return flow and concomitant agrochemical export. Microirrigation systems such as individual container spray stakes provide water directly to crops thus applying water more efficiently than overhead systems but may be more costly in terms of installation (smaller pipes and components; however, a greater quantity of pipes and components) and maintenance. The study was conducted at the Michigan State University Research Nursery, where four ornamental shrub taxa were produced in #3 (11.3 L) containers using a control with 19 mm overhead irrigation per day and a conventional phosphorus fertilizer (19-2.16-6.64), compared with four treatments: a static, daily (2 L per container) spray stake irrigation and conventional phosphorus fertilizer; a static daily (2 L per container) spray stake irrigation and low phosphorus fertilizer (19-1.62-6.64); spray stake irrigation based on substrate volumetric water content (') (up to 2.4 L per container) and conventional fertilizer; and spray stake irrigation based on ' (up to 2.4 L per container) and low phosphorus fertilizer. Spray stakes reduced irrigation by 76-80% compared to the overhead control, and reduced the generation of both surface and subsurface irrigation return flow, mitigating the movement of both N and P. Plant growth index (GI) was measured on 12 June 2017 and 6 October 2017, followed by a destructive harvest to measure shoot dry weight, and shoot nutritional content. For all four taxa, microirrigation systems were capable of producing plants of equivalent GI and shoot nutritional concentration; however, the control typically produced more shoot biomass. Reducing the amount of phosphorus applied to crops did not reduce the amount of phosphorus lost to irrigation return flow relative to the conventional formulation; however, crops typically yielded less shoot biomass under the low phosphorus formulation.