Submitted to: Journal of the American Pomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2008
Publication Date: 10/1/2008
Citation: Ross, D.E., Brauer, D.K. 2008. Seasonal patterns in above ground growth and nut abortion in young eastern black walnut trees in Midwestern United States. Journal of American Pomological Society. 62:191-193.
Interpretive Summary: Eastern black walnut (EBW) is an excellent choice for agroforestry practices in the eastern United States because of its value for nuts and timber. A better understanding of the seasonal growth pattern of EBW may provide insights that will lead to improved management protocols for optimum tree and nut production. ARS scientists at Booneville AR measured the nut diameter, trunk diameter and tree height monthly during the growing season. No significant increase in either trunk diameter or tree height was observed after August. Most nut abortion occurred before August. These results indicate that management protocols need to create an environment that is optimum for EBW growth during the first half of the growing season if tree growth and nut production are to be optimal. These results are of interest to landowners and natural resource professionals that advise landowners.
Technical Abstract: Eastern black walnut (EBW) is an excellent choice for agroforestry practices in the eastern United States because of its value for nuts and timber. There appears to be competing sinks for photosynthate in young trees early in the growing season; however growth data to support such a hypothesis are lacking. This experiment was conducted to provide such data. Monthly variations in nut diameter, trunk diameter and tree height were followed for three stands of EBW that vary in genotype (native versus named genotypes selected for nut quality), age (1 to 12 years-old) and management for two years (2005 and 2006) located within 3 km of each near Booneville AR. In addition, patterns of nut abortion were followed in one stand. Analysis of variance indicated that main effects of years, stands and months significantly affected trunk diameter and tree height. No significant increase in either trunk diameter or tree height was observed after August during the growing season. Most nut abortion occurred before August. These results substantiate the hypothesis that there are competing sinks for photosynthate in young EBW trees early in the growing season. A better understanding of how these sinks compete for photosynthate could lead to management practices that reduce nut abortion and thus increase nut yields in EBW.