Identifying irrigation zones across a 7.5-ha ‘Pinot noir’ vineyard based on the variability of vine water status and multispectral images

Vine water status, yield and berry composition are variables within a vineyard. There is current interest in defining zones of similar yield and berry composition. The aim of this study was to compare two methods for identifying zones of similar yield within a 7.5-ha ‘Pinot noir’ vineyard. The two methods were based on: spatial distribution of average midday leaf water potential (ΨL) and plant cell density (PCD = near-infrared/red) which is a vegetation index. A proposal for splitting the vineyard into eight new irrigation zones was assessed. A ‘blind’ zonation based on regular polygons of equal sizes was also established as a standard for comparison. Coefficients of variation (Cv) in yield for both methods were compared with that of the blind zonation. In 2006 and 2007, a k-means cluster analysis indicated that variability in ΨL was mainly effected by soil properties. In both years, the vineyard was fully irrigated (100 % ETc). The two methods did not improve yield Cv for full irrigation in 2006 and 2007 compared to blind zonation. In 2009, regulated deficit irrigation (RDI) was applied resulting in higher variability in ΨL and yield. The ΨL method of zonation significantly reduced coefficient of variation under RDI but PCD method did not despite the reduction in Cv by 16.7 %. We recommend irrigation zonation based on ΨL when RDI is applied.