Evaluation of crop coefficients, water productivity, and water balance components for wine grapes irrigated at different deficit levels by a sub-surface drip

Abstract

a b s t r a c tAccurate estimation of evapotranspiration (ET) and its partitioning into transpiration and evaporation is fundamental for improving water management practices in water-limited environments and under deficit irrigation conditions. This investigation was conducted to estimate the water balance and ET components of subsurface drip (SDI) irrigated Chardonnay wine grapes for two seasons (2010-2011 and 2011-2012) using a numerical model (HYDRUS-2D). Treatments involved the application of different volumes [51% (I 1 ), 64% (I 2 ), 77% (I 3 ), and 92% (I 4 ) of normal application] of water for irrigation. A modified version of the FAO-56 dual crop coefficient approach was used to generate daily transpiration and evaporation as inputs to the HYDRUS-2D model. The calibrated and validated model produced estimates of actual evapotranspiration (ET Cact ), actual transpiration (T pact ), and actual evaporation (E sact ), and deep percolation under varied irrigation applications. The model-simulated values were then used to estimate actual crop coefficients (K cact and K cbact ), and water productivity of wine grape under different deficit irrigation conditions. Seasonal ET Cact simulated by HYDRUS-2D for different treatments varied between 239 and 382 mm. However, seasonal evaporation accounted for 44-59% of seasonal ET Cact losses in different treatments. The modelled daily transpiration rate in I 4 treatment (T p4act ) varied from 0.11-2.74 mm/day. Deep percolation accounted for 35-40% of the total water applied by rainfall and irrigation. The mean value of actual crop coefficient (K cact ) estimated by HYDRUS-2D simulated ET C act over the two seasons was 0.27, which matched with other investigations. Similarly, values of K cbact for initial, mid and end stages were 0.13, 0.27 and 0.14, respectively. Monthly values of evaporation coefficient (K e ) ranged from 0.1 to 0.32, with a mean value of 0.18. Water productivity with respect to ET losses (WPET C ) ranged from 5.9 to 6.2 kg/m 3 of water use. However, water productivity for transpiration (WPT C ) almost doubled as compared to WPET C in all treatments. The impact of deficit irrigation on berry juice composition (Brix, pH and titratable acidity) was lower than the inter-seasonal variability. These results can help develop better irrigation management strategies for SDI irrigated wine grapes under water scarce conditions.

Identifying the future water and salinity risks to irrigated viticulture in the Murray-Darling Basin, South Australia

“…Total amount of irrigation thus applied (10 mm/day/event) is similar to the amount normally applied to grapevine in the Loxton region (ICMS, 2007). The trigger point in this study was located at a 30-cm soil depth, which is similar to other field (Soar and Loveys, 2007) and modeling (Phogat et al, 2017) studies in this region and coincides with the maximum root activity for viticulture. Other studies also used a similar suction for irrigating grapevines (Edwards and Clingeleffer, 2013) at a 30-cm soil depth for well-watered conditions.…”

“…The soil hydraulic parameters used in this investigation are given in Table 1. Similar hydraulic parameters have also been used in other related studies (Phogat et al, 2016(Phogat et al, , 2017 in the Riverland where HYDRUS has been calibrated and validated for spatiotemporal water content distribution in the soil under viticulture.…”

“…These studies demonstrated that this approach could be successfully used in environments under intensive irrigation and fertigation management. The longitudinal dispersivity was assumed to be one tenth of the modeling domain (Cote et al, 2003) and the molecular diffusion coefficient for salts in water was considered to be 1.66 cm 2 /day (Phogat et al, 2014(Phogat et al, , 2017. Since it is difficult to predict changes in the river water quality under the future climate change, the EC iw data for irrigation water was based on the water (Cresswell et al, 2010) and was adapted in the present modeling investigation.…”

“…The effect of water and salinity stresses was assumed to be multiplicative so that different stress response functions could be used for water and salinity stresses. Critical values of pressure heads for root water uptake were taken from previous investigations on grapevine (Phogat et al, 2017) in the study area. The threshold and slope model parameters were obtained from the previous regional study (Zhang et al, 2002) evaluating salinity thresholds (EC e = 2.1 dS/m) and percent reductions (12.8%) in different root stocks of grapevine.…”

“…The simulation domain depth was selected based on the maximum rooting depth of grapevine (100 cm) reported in the literature and previous modeling studies on grapevine in the study area (e.g., Phogat et al, 2017). Measured values from the experimental site were used as the initial conditions for water content and soil solution salinity (EC sw ) for current climate (2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015).…”