Vineyard management is based on uniform application of irrigation water across an entire vineyard to ensure that each vine receives the same amount of water. However, in some parts of a vineyard, vines may be over-irrigated, while in other parts they may suffer from water stress. This occurs due to differences in soil properties and topography. In coarser soil, water-holding capacity is lower. Therefore, vines located in this type of soil are often less vigorous than those in heavier soil, where water-holding capacity is higher. For vineyards with varied topography, yields from higher and lower spots can differ by up to 10-fold (Bramley and Lamb, 2003).Considering these factors, certain areas in a field may require tailored irrigation scheduling in order to attain uniform vine canopy size. Until now, no commercial drip irrigation system has successfully carried out differential irrigation across an entire vineyard. Several studies aiming to achieve differential irrigation have included sensor-triggered systems in greenhouses (Lichtenberg et al, 2013) and small-scale open field crop systems (Kamel et al., 2012). The most popular study of variable rate irrigation involved center pivot-irrigated crops (Patil and Al-Gaadi, 2012). Differential drip irrigation studies based on canopy size, yield map and vine water potential have also been conducted in Australia (McClymont et al., 2012; Proffitt and Pearce 2004) and Spain (Bellvert et al., 2012; Martínez-Casasnovas et al., 2009). In both of these latter studies, the vineyard was divided into management zones, and each zone was irrigated according to its needs. In the Australian study, variability reduction in both vegetative growth and yield occurred, while in Spain there was no reduction in yield variability. Modifying the number of drippers per vine can result in different amounts of water applied, but it lacks the flexibility to schedule irrigation differently for each vine; hence, a more sophisticated system needs to be designed. The most advanced system of variable rate irrigation for vineyards was reported by Sanchez et al., (2014), which resulted in decreased variability in both NDVI and yield in a VRI irrigated plot in comparison to a control of uniform irrigation.
The aim of the study was to implement a variable irrigation rate in vineyards by applying different amounts of water in different areas across the field, using Normalized differential vegetation index (NDVI) and water potential-based model, to reduce the spatial variability in both yield and quality.
By Nadav, Netafim, R&D Center, Derech Hashalom 10, Tel Aviv, Israel