|Brauer, David - Dave|
Submitted to: Agroforestry Systems
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/29/2005
Publication Date: 4/1/2006
Citation: Brauer, D.K., Ares, A., Reid, W., Thomas, A., Slusher, J.P. 2006. Nut-yield varieties and dbh-nut yield relationships in open canopy black walnuts in southern USA. Agroforestry Systems. 67:63-62. Interpretive Summary: Many landowners in the United States have little knowledge of the potential economics returns from eastern black walnut agroforestry practices and this lack of knowledge may limit the establishment of walnut plantings. Sources of the variation in walnut yields are poorly understood thus models predicting economic returns from this tree species cannot be constructed. The objectives of this study were to characterize variations in nuts yields among eastern black walnut trees in 3 data sets and apply this information to the development of predictive equations between tree diameter and nut yields. Variations in nut yields were quite high for trees in a stand and between stands, and for a tree over time; however, responsibly accurate predictive estimates of nut yields over a 2 to 4 year period could be constructed from the stand's average tree diameter. These results represent the first step in creating economic models for black walnut agroforestry practices, which should be of interest to natural resource and timber professionals, and landowners interested in establishing black walnut plantings.
Technical Abstract: Many landowners in the United States have little knowledge of the potential economics returns from agroforestry practices. Economic simulators for temperate agroforestry practices have been generated; yet, there are few data sets on yields of timber and other products to run, validate and refine such models. The objectives of this study were to characterize variations in nuts yields among eastern black walnut (Juglans nigra L.) trees and apply this information to the development of predictive equations between tree diameter at breast height (DBH) and nut yields. Three data sets were analyzed that included results from Tennessee, Chetopa, Kansas and Mt Vernon, Missouri. Tree-to-tree variation in nut yields was high within each data set, with coefficient of variations for nut yields, typically exceeding 50%. Averaging nut yields over several consecutive years reduced coefficients of variation. Nearly half of the high nut producing trees exhibited biennial pattern of alternate bearing of nuts. Trees with low average nut yields had either sporadic or irregular patterns of nut bearing. The regression coefficients for equations relating stem diameter and nut yields varied considerably. Averaging nut yields over consecutive years, and averaging stem diameter and nut yields over a number of trees increased regression coefficients of such equations. These results indicate that predicting nut yields of a tree stand over a several year-period will be easier than predicting yields for a specific tree in a specific year.