Submitted to: Southern Nursery Association Research Conference
Publication Type: Proceedings
Publication Acceptance Date: 8/1/2004
Publication Date: 8/1/2004
Citation: Fain, G.B., Paridon, K., Hudson, P. 2004. The effect of cylic irrigation and herbicide on plant and weed growth in production of magnolia grandiflora 'alta". Southern Nursery Association Research Conference. 49:37-39
Interpretive Summary: This research was conducted to indicate what effect cyclic irrigation might have on herbicide efficacy. Irrigation was applied in a single application, divided into three applications with a two hour resting interval between applications, or divided into six applications with a one hour resting interval between applications. While cyclic irrigation did increase height and caliper of Magnolia grandiflora 'Alta', cyclic irrigation also reduced herbicide efficacy, relulting in greater weed populations. Growers should be aware that a possible side effect of converting to cyclic irrigation is a reduction in herbicide longevity and efficacy. This may result in an increase in the amount of hand weeding needed or an increase in the frequency of herbicide applications.
Technical Abstract: Past research has shown the benefit of cyclic irrigation in production of nursery plants. Research has indicated that the proper use of cyclic irrigation can increase water and fertilizer use efficiency as well as increasing plant growth. However no research has been conducted to indicate what effect cyclic irrigation might have on herbicide efficacy. An experiment was conducted to evaluate the effect of cyclic irrigation (dividing the plants daily water allotment into more than one application with resting intervals between applications) and herbicide formulations on plant and weed growth in production of Magnolia grandiflora 'Alta'. On March 21, 2003, one quart Magnolia grandiflora 'Alta' liners were potted into #7 containers using a standard nursery mix. Polyon 17N-2.9P-9.8K was dibbled (placed 7.6 cm below the surface of the container media at potting) at 210 g per container. Irrigation was applied using a spray stake attached to an 11.4 liter per hour pressure compensating drip emitter. Irrigation was applied in a single application, divided into three applications with a two hour resting interval between applications, or divided into six applications with a one hour resting interval between applications. All plants received approximately 2.3 liters of water daily. Herbicides were Rout (oxyfluorfen + oryzalin), Snapshot (trifluralin + isoxaben), or Regal O-O (oxyfluorfen + oxidiazon). All herbicides were applied at the label recommended rate. Herbicides were applied on March 28. On March 31 containers were over-seeded with 20 prostrate spurge seed (Chamaesyce prostrata). Herbicide formulation had no effect on plant or weed growth. Irrigation treatment had a significant effect on plant height and caliper increase. On October 20 plants receiving six irrigation applications had on average a 21% greater height increase and a 14% greater caliper increase than those receiving one or three applications. Irrigation treatment also had a significant effect on weed top dry weight. At 90 DAST plants receiving three and six irrigation applications had 261% and 285% greater weed top dry weight respectively than those receiving one application. Growers using cyclic irrigation should be aware of its effect on herbicide efficacy. Dividing the plants daily water allotment into six applications produced larger Magnolia grandiflora 'Alta' despite the increase in weed infestation.