Biology subjects

Phogat, V.

Publications and source records attributed to Phogat, V..

3 recordsLinked to original sources

bioRxiv2024

Regional dynamics in the evapotranspiration components, crop coefficients and water stress in vineyards in the Barossa Valley

Estimation of water balance components, water stress and crop coefficients at different spatial scale are crucial for understanding regional dynamics in irrigation requirement and crop water use. We estimated these parameters for irrigated vineyards over 3 consecutive seasons (2018-19, 2019-20 and 2020-21) at 48 locations in the Barossa region, South Australia. We used FAO-56 dual crop coefficient approach by integrating relevant data for soil, crop, and climate parameters from the study sites. Numerous statistical error estimates, and efficiency parameters were estimated to compare and verify the predictions by FAO-56 approach. Results show a huge variability in the irrigation, water balance parameters, crop and water stress coefficients, and water productivity parameters. For instance, a coefficient of variation ranging from 20 to 97% was observed in daily and seasonal actual ET (ETc act) across different sites and seasons. Average actual transpiration (Tp act) and evaporation (Es) account for around 65 and 35% of the ETc act, respectively, showing the potential to save water lost to the environment from the soil surface. Estimated actual single crop coefficient (Kc act) across all sites varied from 0.35 to 0.59, 0.16-0.62 and 0.18-0.68 during the budburst to flowering (BB-FL), flowering to veraison (FL-V), and veraison to harvest (V-H) stages of crop growth, respectively. Similarly, actual basal crop coefficients (Kcb act) for grapevine reveal immense site-specific variability questioning the adoption of uniform coefficients at subregional and regional levels. Results further demonstrate that water stress (Ks) gradually increased reaching its peak from late November to early December, with variations across the region ranging from 23 to 64%. A comparison of water productivities in relation to ETc act and Tp act exhibit almost 61% higher values for the latter across all the sites and subregions. Dry biomass productivity shows huge potential for renewal energy generation. Variations in the components of ET and crop coefficients are consistent with the characteristic variation in soil, topography, and microclimates. This study suggests that locally estimated Kc act and Kcb act will contribute to the efficient use of limited freshwater resources for sustainable wine grape production.

plant biology↗

bioRxiv2022

Benchmarking water-limited yield potential and yield gaps of Shiraz in the Barossa and Eden Valleys

Background and AimsVineyard performance is impacted by water availability including the amount and seasonality of rainfall and evapotranspiration and irrigation volume. We benchmarked water-limited yield potential (Yw), calculated yield gaps as the difference between Yw and actual yield, and explored the underlying environmental and management causes of these gaps. Methods and ResultsThe yield and its components in two sections of 24 Shiraz vineyards was monitored during three vintages in the Barossa zone (GI). The frequency distribution of yield was L-shaped, with half the vineyards below 5.2 t ha-1, and an extended tail of the distribution that reached 24.9 t ha-1. The seasonal ratio of actual crop evapotranspiration and reference evapotranspiration was below 0.48 in 85% of cases, with a maximum of 0.65, highlighting a substantial water deficit in these vineyards. A boundary function relating actual yield and seasonal rainfall was fitted to quantify Yw. Yield gaps increased with increasing vine water deficit, quantified by the carbon isotope composition in the fruit. The yield gap was smaller with higher rainfall before budburst, putatively favouring early-season vegetative growth and allocation to reproduction, and with higher rainfall between flowering and veraison, putatively favouring fruit set and berry growth. The gap was larger with higher rainfall and lower radiation between budburst and flowering. The yield gap increased linearly with vine age between 6 and 33 yr at a rate of 0.3 t ha-1 yr-1. The correlation between yield gap and yield components ranked bunch weight {approx} berries per bunch > bunch number > berry weight; the minimum to close the yield gap was 185,000 bunches ha-1, 105 g bunch-1, 108 berries bunch-1 and 1.1 g berry-1. ConclusionsWater deficit and vine age were major causes of yield gaps. Winter irrigation provides an opportunity to improve productivity. The cost of dealing with older, less productive vines needs to be weighed against the rate of increase in yield gap with vine age. Significance of the StudyA boundary function to estimate water-limited yield potential returned viticulturally meaningful yield gaps and highlighted potential targets to improve vineyard productivity.

plant biology↗

bioRxiv2022

THE RELATIONSHIP BETWEEN TERROIR AND THE PHENOLOGY OF BAROSSA SHIRAZ

Background and AimsVine phenology results from the interaction between the genotype, environment and management, with implications for fruit, and wine composition. The impact of weather, site and management practices, underlying elements of terroir, impacting the timing of key phenological stages were explored across the Barossa Zone (GI). Methods and ResultsVine phenology was assessed in three zones of 24 vineyards over three vintages using the E-L scale before veraison, and total soluble sugars (TSS) in berries during ripening. We explored the associations between weather, plant traits and viticultural variables, and development in four periods: pre-budburst, budburst-flowering, flowering-veraison and veraison-maturity. The spatial structure of the timing of phenological events suggested three main groups of vineyards. This structure followed gradients in topography and soils across the landscape, and were maintained despite the effect of the season (vintage). On average, differences between early and late groups of vineyards were 13 days at budburst, 20 days at flowering and 24 days at TSS = 24 {degrees}Brix. Phenology responded mainly to temperature until flowering, and to temperature and canopy size from flowering to maturity. The strength of the relationship between the duration of the period and temperature ranked pre-budburst (r2 = 0.94) > budburst-flowering (r2 = 0.40) > veraison-maturity (r2 = 0.17). Duration of pre-budburst and budburst-flowering periods was shortened at 6 d {degrees}C-1, compared to 2 d {degrees}C-1 for veraison-maturity. The duration from veraison to maturity increased with yield (r2 = 0.29, Pa < 0.0001). ConclusionsThe spatial variation in development was maintained despite vintage effects and management practices. Variation in temperature due to topography and elevation were the major drivers of vine phenological development until flowering. During ripening, development was driven by temperature and carbon capture and partitioning. Significance of the StudyThis is the first attempt to show spatial variability on phenology across the Barossa Valley GI. The observed switch on drivers on phenology during development from temperature-driven processed before flowering to resource-dominated processes during ripening have implications for modelling and vineyard management.

plant biology↗