How Much Weed Control is Necessary for Establishment of Black Walnut Seedlings in Tall Fescue Silvopasture?.

Silvopasture – the integration of trees, forage, and livestock, can be established by thinning existing forested stands or by planting trees in existing pastures. In Missouri, successful tree establishment and acceptable growth in tall fescue pastures requires chemical weed control. Current recommendations vary widely with some suggesting weed control zones should extend as much as 2.4 m from tree seedlings. More defined guidelines are necessary to minimize weed control costs and optimize land use. This study was conducted to determine how much weed control is necessary for the establishment of black walnut (Juglans nigra L.) in tall fescue (Lolium arundinaceum Shreb. SJ Darbyshire) pastures in Missouri. ‘Half-sib’ black walnut seeds were planted in six different sized vegetation-free zones (0.30, 0.61, 0.91, 1.21, 1.52, and 1.81 m in radius) in tall fescue pastures created and maintained by applying glyphosate.  A no-herbicide control was also used. The study was planted two consecutive years at two locations in central and north-central Missouri differing in soil types. The study areas were mowed to a height of 10 cm prior to planting and twice during the growing season. Data were taken on seedling height and diameter. Height growth was greatest in zones 0.91 m and larger. Growth in these zones was similar to each other and significantly greater than that in smaller zones. Diameter growth was greatest in 1.21 m zones and larger. Growth in these zones was similar to each other and significantly greater than that in smaller zones. These results suggest that weed control should extend a minimum of 1.21 m from black walnut seedlings in tall fescue pastures to maximize height and diameter growth. More weed control may not result in greater tree growth, but would require greater weed control costs and remove more land from forage production.