Six weed control programmes with and without irrigation were investigated in a newly established pecan orchard. The irrigation increased the crown diameter growth in only one of the seven growing seasons but increased the nut yield by an average of 35 in the first two bearing years. The weed control programme significantly influenced the crown diameter beginning in the fourth growing season and continued through season six while also impacting the final crown diameter. The use of post-emergence (POST) herbicides increased the crown diameter by a minimum 4 mm vs. pre-emergence (PRE) herbicides. Mowing neither increased nor decreased the crown diameter when used with the herbicides; however, when used solely, the crown diameter was 29 less. The highest growth rates were obtained with a combination of PRE plus POST weed management system. The nut yields were closely linked to the growth data. No differences in nut yield were observed between the PRE- or POST-herbicide programmes alone or in combination with mowing. Mowing alone decreased nut yield by 57 vs. herbicide-based approaches. A combination of PRE- plus POST-weed control programme increased the yield by 38 vs. all other treatments.
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