CHANDLER WALNUT HEDGEROW PRUNING AND TRAINING TRIAL 2013

Hedgerow walnut orchards have been studied since the 1970s as a high density system to reduce pruning costs and to benefit early production. At present, the common pruning methods are similar to the methods used to establish conventionally spaced orchards with some differences in heading height of the trunk and height of the first scaffold selected and the amount of wood removed in the early years. This trial looks at ways to improve this pruning method to gain a better tree structure, improve the amount of fruit wood, decrease wind damage and potentially reduce the need for early hedging of the orchard. Four hedgerow training systems were implemented starting in 2009 after the first season of growth; heavily pruned, minimally pruned, minimally pruned with restricted irrigation and unpruned. Tree growth characteristics of diameter, height, canopy size (light interception), and yield were measured in 2009-2013. Plant water status was measured using midday stem water potential throughout the growing season. 2013 Chandler results show a difference in average circumference and height, with the heavily pruned treatment being significantly smaller and shorter than the minimally pruned treatment and the untrained/unpruned treatment but no significant difference in PAR interception, yield, cumulative yield, or yield per unit PAR intercepted among treatments in 2013. In 2012-2013, unlike in earlier years, the midday stem water potential of the Chandlers showed no significant difference between treatments throughout the season although the unpruned treatment tended to be the least stressed and the deficit irrigation treatment tended to be more stressed than the other treatments on most dates, particularly early in the season.