Evaluation of Organic Weed Control Methods in Pecan Production

Rising demand for organic commodities has led to the reevaluation of standard agricultural practices in order to meet this demand. In order for organic pecan production to be a viable enterprise several factors must be addressed in pecan cultivation including orchard floor management. Traditionally, in pecan orchards, a large portion of each row is maintained weed-free with herbicide applications while vegetation between rows is regularly mowed. An experiment was conducted from 28 September 2013 to 24 July 2015 to determine efficacy of organic weed control methods in pecan orchards. Evaluated methods included mowed sod, flame control, pine bark mulch, vinegar herbicide, and pine bark mulch in combination with vinegar herbicide. Mowing, flame control, and vinegar herbicide were applied at regular intervals during the course of the experiment while pine bark mulch was applied once at experiment initiation. Data were collected at each treatment application date. Large dicotyledonous species including Cinnamomum camphora (L.) Siebold, Sapium sebiferum (L.) Roxburgh, and Rubus spp. were hand removed from plots, as needed. The experiment was a randomized complete block design with five blocks. Data were subjected to analysis of variance in JMP Pro 12 and means were separated using Tukey’s HSD (α = 0.05). The combination of pine bark mulch and vinegar herbicide improved weed control in plots compared with other treatments. Plots were kept, on average, 70% weed-free with combination of pine bark and vinegar herbicide compared with only 15, 41, 50, and 27% for mowed sod, flame control, pine bark mulch (alone), and vinegar herbicide (alone), respectively. Weed species varied in prevalence in treated plots but all treatments decreased prevalence of dicotyledonous species compared with mowing which provided the least control. Bermudagrass (Cynodon dactylon (L.) Persoon) was the most prevalent monocot species and was controlled most effectively by the combination of pine bark and vinegar. Although pine bark mulch, especially in combination with vinegar herbicide, provided the best weed control, bark interfered with pecan harvest. Pine bark in combination with vinegar herbicide is the best available organic option for weed control, but should be limited to use during orchard establishment. Regular mowing, while not especially effective in weed control, is the best option evaluated for floor management in a mature, organic pecan orchard.