Location: Application Technology Research
Project Number: 5082-21000-001-014-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 15, 2018
End Date: Sep 14, 2023
Objective:
We will investigate nursery irrigation water as a potential source for weed seed distribution in container nurseries in the eastern U.S.
Approach:
Irrigation water will be screened at multiple nurseries to assess the species and number of weed seeds present before and after nursery water filtration. Sites will be selected for differences in irrigation water management practices – such as no filtration, sand filtration, sanitizing treatment, and the use of a settling pond (+/-).
1. Irrigation water will be passively sampled using in-line filters. Volume of water will be monitored and filters replaced monthly. Residue on the filters will be viewed under a microscope to assess the presence or absence of weed seeds. Weed seeds in the residue will be germinated, counted and identified. Preliminary testing will determine exact bioassay protocol for this sampling. It is anticipated that samples will be placed in petri dishes with blotter paper, then placed in a germination chamber set at day 30 C (86F) and night 20C (68F) temperatures with a 18 hr day and 6 hr night photoperiod. Germination will be counted weekly for 2 weeks. For species which cannot be identified to species by seed or at the early growth stages will be grown in the greenhouse for identification.
a. Additional sampling methods, such as end-point irrigation riser capture or drip line capture) will be assessed for sampling efficiency. Additionally, irrigation water volume, collection times and screen sizes will be compared.
2. Survival of weed seeds submerged in source water used for irrigation, but differing in ionic quality.
Based on Objective 1 above, fresh seeds of weed species identified within the irrigation water will be submerged in mesh bags at the intake level of the pond pump for 0, 1, 2, 7, 14, 21, 28, 60, 90, 120, 190, and 365 days then removed and germinated under conditions described in Objective 1. An additional set of similar seeds will be stored and germinated at the sampling times to gauge optimal germination rate for each species.
During a grower workshop, one of the stakeholders stated, “The poorer the irrigation water, the less likely they were to have algae and other problems. When water was perfect, weeds like liverwort were the worst.” Therefore, we will determine differences in ionic water quality between the cooperating nurseries and recreate those samples in the lab to test the theory. Mainly we will concentrate on alkalinity and common hardness ratings, N and P levels, as well as dissolved oxygen concentrations found in pond water throughout the U.S. (Meador et al. 2012; Zhang et al. 2016; Copes et al. 2017, 2018). In lab submerge seeds for same time frame as listed above in created water that most closely resembles pond water of cooperating nurseries in salts, alkalinity, dissolved oxygen and pH then germinate them. This corroborates the in nursery submersion and lets us know if some known factors like pH or alkalinity might affects seeds if submerged in ponds near intake.
The time frames used in Objective 1 will allow us to survey weed seeds in irrigation water over the life cycle of annual, perennial and woody weed species within and surrounding the nurseries.
