Plant Cell Density Research Articles

Spatially variable pesticide application in vineyards: Part II, field comparison of uniform and map-based variable dose treatments

Reducing pesticide use is an important concern for many including the European Commission. One way to achieve this goal is to adjust the amount of pesticides in relation to canopy geometry and foliage. This objective currently poses an important challenge in vineyards with uniform vegetation but it is an added difficulty when the canopy shows spatial variability within the field. Is it possible to set a constant volume rate adjusted to this variability? Or is it more convenient to adjusting different volume rates based on a prescription map? Assuming a plant cell density (PCD) vegetation index from multispectral images to be optimal for detecting variations in vigour, two methods to adjust volume rates in spatially variable vineyards were proposed and tested: i) adjustment of a constant volume rate uniformly applied using a conventional sprayer, and ii) adjustment of two volume rates adapted to two vigour classes according to a prescription map. In both methods, PCD was previously correlated to the leaf area index (LAI), then taking the 70th percentile of LAI to determine adjusted volume rates through DOSA3D decision support system (www.dosa3d.cat/en). Leaf deposition with tracer was analysed to compare the proposed methods with the standard volume rate commonly used in the area. Statistical analysis showed no significant differences between treatments. Since pesticide savings can be achieved using the two methods, specifically 25.6% in adjusted uniform and 25.3% in adjusted map-based treatments, adjusted volume rate strategies can be recommended in vineyards with spatial variability.

Pinot Noir wine composition from different vine vigour zones classified by remote imaging technology

The relationship between grapevine vigour and grape and wine composition was investigated in this study. Own-rooted Pinot Noir grapevines were grown in a commercial vineyard in Tasmania, Australia, with uniform vineyard management practices. Vine vigours were determined by plant cell density (PCD) obtained from aerial photography. As vine vigour decreased, total soluble solid in grapes, total phenolics and anthocyanins in wines increased, while titratable acidity and yield decreased. Wines from the ultra low vine vigour zone had the highest concentrations of esters and alcohols. Higher level of linalool, nerol, geraniol, vitispirane, and β-ionone were observed in ultra low vigour and low vigour zones, but there was no obvious trend for citronellol and β-damascenone. Principal component analysis and discriminant analysis of the volatiles illustrated the differences among wines from the four vine vigour zones.

IS PCD A RELIABLE INDICATOR OF BERRY QUALITY ATTRIBUTES IN WATER STRESSED VINEYARDS?

Grape berry composition in terms of sugars and titratable acidity is strongly dependent on vine water status. The objective of this study was to evaluate the feasibility of using airborne derived Plant Cell Density (PCD) and canopy reflectance derived Simple Ratio (SR) measurements – both remote indicators of leaf area and intercepted light – at estimating berry yield and composition in vineyards experiencing water deficits. In addition, the capability of the Water Index (WI) – a hyperspectral reflectance based indicator of water status – derived from canopy reflectance at estimating berry yield and composition was tested. The study was conducted in vineyards of Vitis vinifera L. ‘Chardonnay’. Remote optical imagery was acquired at veraison and PCD derived. Field measurements of fractional intercepted Photosynthetic Active Radiation (fIPAR), predawn water potential (Ψp), canopy to air temperature difference at midday (ΔT(midday)) and canopy hyperspectral reflectance were also conducted at the stage of veraison. Yield, Total Soluble Solids (TSS), Titratable Acidity (TA) and maturation index (IMAD) were determined at harvest. Predawn water potential ranged from -0.85±0.06 MPa to -0.50±0.07 MPa among the vineyards studied indicating moderate to severe water stress at the stage of veraison. Berry quality attributes did not show significant relationships against fIPAR but were related to ΔT(midday) in a variable extend. Consistently, PCD derived from airborne imagery, as well as the SR, did not show significant correlation against berry quality attributes. On the other hand, the WI derived from canopy reflectance showed significant correlation against ΔT(midday) (r = -0.82, P<0.05) and successfully estimated TA and IMAD (r = 0.70, P<0.05, for both indices). The results obtained suggest that, in vineyards experiencing water deficits, remote estimates of vine water status through the WI might be more appropriate to characterize berry composition than remote estimates of vine vigor such as SR or PCD.