Larry E. Williams

A comparative study of young ‘Thompson Seedless’ grapevines under drip and furrow irrigation. I. Root and soil water distributions

Abstract Soilwater distribution, soilwater extraction, and root distributions were determined for young grapevines ( Vitis vinifera L. cultivar ‘Thompson Seedless’) grown under drip and furrow irrigation near Fresno, CA, USA. Soilwater content and extraction was determined to a depth of 0.9 m by neutron scattering from an array of nine access tubes installed throughout one-quarter of the soil volume available to each vine. Root distribution was determined from root intersections with vertical planes established parallel and perpendicular to the vine row. Drip irrigation was applied daily according to estimated evapotranspiration, and furrow irrigation was managed according to 50% depletion of the plant available soil water. Drip and furrow irrigated vines showed similar water status and shoot growth patterns. There was a confined soil wetted zone beneath the emitter discharge that largely coincided with a confined and shallow root system of drip irrigated vines. In contrast, furrow irrigated vines had a deeper and more widespread root system. Differences between water applied and soilwater content 3 days after irrigation suggested large water losses by evaporation during that period for furrow irrigated vines. Consumptive use of furrow irrigated vines was 12.5% greater than drip irrigated vines, but similar irrigation efficiencies were obtained for both irrigation systems when soilwater status was carefully monitored. Water applications for both irrigation systems were less than 50% of the longterm mean for irrigation deliveries to farms in the area. Thus, the results indicate that a significant potential for water savings exists in the San Joaquin Valley by means of irrigation management. It is concluded that relatively high and similar irrigation efficiency can be obtained with both drip and furrow irrigation of young grapevines in arid and semiarid regions when careful management is used.

2-Methoxy-3-isobutylpyrazine in grape berries and its dependence on genotype

2-Methoxy-3-isobutylpyrazine (MIBP) contributes a bell pepper aroma to many grape cultivars and has a reported aroma threshold of ∼2 ng L(-1) in water. The purpose of this study was twofold: (1) develop a procedure using headspace solid phase micro-extraction combined with GC-MS in the selected ion monitoring mode (HS-SPME-GC-MS-SIM) for analysis of MIBP in grape berries, and (2) determine the location of MIBP biosynthesis in grapevines by approach grafting clusters of Vitis vinifera L. cvs Cabernet Sauvignon and Muscat blanc onto each other. The soluble solids and pH of the grape juice/homogenate matrix from different grape berry developmental stages influenced the method precision; therefore, quantification via the method of standard addition was used. Using our developed method, the limit of detection (LOD) and limit of quantitation (LOQ) of MIBP were 0.1 ng L(-1) and 2 ng L(-1), respectively, measured in a model juice and non-MIBP containing Chardonnay juice. Spiked recoveries averaged between 91% and 112% in Cabernet Sauvignon and Pinot noir homogenates and the overall relative standard deviation was less than 10%. The method was used to analyze MIBP in 29 grape cultivars and in fruit from clusters grafted to Cabernet Sauvignon or Muscat vines. Quantifiable levels were found only in Cabernet franc, Cabernet Sauvignon, Merlot, Sauvignon blanc and Semillon, providing information on the genetic connection for the occurrence of MIBP in grapes. No MIBP was detected in the berries of Muscat blanc clusters grafted onto Cabernet Sauvignon vines when sampled at fruit maturity. MIBP was detected in all berries of Cabernet Sauvignon regardless the graft configuration. The data indicate that MIBP or its precursors originate in the berry and its formation depends upon grape genotype.

A comparative study of young ‘Thompson Seedless’ grapevines (Vitis vinifera L.) under drip and furrow irrigation. II. Growth, water use efficiency and nitrogen partitioning

The response of 3-year-old grapevines (Vitis vinifera L. cultivar ‘Thompson Seedless’) to furrow and drip irrigation was quantified in terms of water status, growth, and water use efficiency (WUE). Drip irrigation was applied daily according to best estimates of vineyard evapotranspiration while furrow irrigations were applied when 50% of the plant available soilwater content had been depleted. Drip and furrow irrigated vines showed similar water status (midday leaf water potential, Ψ1) and shoot growth patterns throughout the season. Dry weight partitioning was not significantly different between treatments but root mass was somewhat larger for the furrow than drip irrigated vines. Nitrogen concentrations of the fruit and roots were significantly (P < 0.05) less for the drip irrigated vines when compared with the furrow treatment. Similar WUE (kg water kg−1 fresh fruit wt.) were obtained for both treatments indicating that furrow irrigation was as efficient as drip irrigation under the conditions of this study. The data indicate that drip irrigation may increase the potential for control of vine growth by making vines more dependent on irrigation and N fertilization than furrow irrigation.

Fruit ripening in Vitis vinifera: light intensity before and not during ripening determines the concentration of 2‐methoxy‐3‐isobutylpyrazine in Cabernet Sauvignon berries

The roles of light and temperature in the accumulation of the vegetal impact compound 2-methoxy-3-isobutylpyrazine (MIBP) in grape (Vitis vinifera L.) berries were determined. Individual clusters were exposed to various light intensities using neutral density shade cloth before ripening, during ripening or throughout the season in three growing seasons. A recently developed method using headspace solid-phase microextraction combined with GC-MS in the selected ion-monitoring mode was employed to measure MIBP in berries. Berry MIBP concentration increased subsequent to berry set, reached a maximum prior to onset of ripening, and then decreased thereafter until harvest. Complete shading of clusters increased the concentration of MIBP more than 100% compared to unshaded controls in 2 out of 3 years. Light increasingly inhibited MIBP concentrations up to 25-50% of ambient light intensities (1500 µmol photons m(-2) s(-1) ). However, only changes in light intensity before ripening had any effect on MIBP accumulation or final MIBP concentration. Analyses of weather data showed that the 1 year in which shading was ineffective was unusually warm, warm early in the season, and had more hot days and higher early season degree days than the other 2 years. In controlled environment experiments, warm growth conditions reduced MIBP concentrations in fruit about as much as light exposure reduced MIBP concentrations in the field experiments. The results indicate that both light and temperature significantly affect MIBP in harvested fruit, but that the light environment during ripening does not significantly affect MIBP concentrations in the berries at harvest.

Effect of Applied Water Amounts at Various Fractions of Evapotranspiration on Productivity and Water Footprint of Chardonnay Grapevines

The effects of irrigation treatments with applied water amounts at various fractions of crop evapotranspiration (ETc) on productivity of Chardonnay grapevines grafted onto two rootstocks were determined across eight years. Irrigation treatments during the first four years were applied water amounts at 0.25, 0.5, 0.75, 1.0, and 1.25 of ETc while those in subsequent years were a no applied water treatment and applied water amounts at 0.5 and 1.0 of ETc. Grapevine water use was determined using the soil water balance method. Year had a significant effect on all measured parameters (berry weight, soluble solids, pH, titratable acidity, and yield and its components). The highest (21.9 t/ha) and lowest (11.6 t/ha) yields differed almost two-fold across years. While rootstock had a significant effect on some of the above parameters, they were not consistent among years and there were only a few instances in which there was a rootstock by irrigation interaction. Yield per unit applied water averaged 4.43 and 13.7 t/ML for the 1.25 and 0.25 irrigation treatments while yield per unit ETc averaged 4.28 and 6.45 t/ML for the 1.25 and 0.25 treatments, respectively. The high and low water footprint values per unit ETc ranged from 130 to 400 m3 of water/t across the duration of the study. The large difference in the water footprint from year to year was due to differences in yield. The water footprint for the no applied water treatment was 166 m3/t in 1998 and 228 m3/t in 1999. The fact that the water footprint reported here is lower than published values for grapevines may have been due to higher yields and better estimates of vineyard ETc.

Determination of Evapotranspiration and Crop Coefficients for a Chardonnay Vineyard Located in a Cool Climate

A study was conducted in a Chardonnay vineyard located in the Carneros district of Napa Valley to derive vineyard evapotranspiration (ETc) and seasonal crop coefficients (Kc) values. The vineyard was planted on 2.13 m rows, using a vertical shoot-positioned trellis. Vineyard ETc was measured using the soil water balance method. Soil water content (SWC) was measured in one-fourth of an individual vine’s soil profile (six access tubes per site) to a depth of 2.75 m. In addition, vines were irrigated with applied water amounts at 0.25, 0.5, 0.75, 1.0, and 1.25 of estimated vineyard ETc. Vineyard ETc the first year of the study was ~400 mm. Thereafter calculated vineyard ETc (the product of reference ET [ETo] and the Kc) ranged from 346 to 503 mm per season. Midday leaf water potential (Ψl), leaf net CO2 assimilation rate (A), and stomatal conductance (gs) were used to indirectly validate estimated ETc (to determine that vines were not stressed for water) and the derived Kc values. Midday Ψl, A, and gs were linearly related with applied water amounts and SWC across irrigation treatments and years. The diurnal measurements of A and gs resulted in differences among irrigation treatments, from early morning until late afternoon, with significant differences among treatments dependent upon actual applied water amounts. The results from this study are the first in which vineyard ETc has been measured on vines grown at a cool vineyard site in California. Estimates of ETc from this study would be valid for a vineyard with a row spacing of 2.13 m and a canopy vertically positioned using a maximum Kc of 0.74.

Evaluating the potential of a novel dual heat-pulse sensor to measure volumetric water use in grapevines under a range of flow conditions

The aim of this study was to validate a novel, dual sap-flow sensor that combines two heat-pulse techniques in a single set of sensor probes to measure volumetric water use over the full range of sap flows found in grapevines. The heat ratio method (HRM), which works well at measuring low and reverse flows, was combined with the compensation heat-pulse method (CHPM) that captures moderate to high flows. Sap-flow measurements were performed on Vitis vinifera L. (cvv. Thompson seedless, Chardonnay and Cabernet Sauvignon) grapevines growing in a greenhouse and in three different vineyards, one of which contained a field weighing lysimeter. The combined heat-pulse techniques closely tracked diurnal grapevine water use determined through lysimetry in two growing seasons, and this was true even at very high flow rates (>6L vine-1h-1 for Thompson seedless vines in the weighing lysimeter). Measurements made with the HRM technique under low flow conditions were highly correlated (R2 ~ 0.90) with those calculated using the compensated average gradient method that is used to resolve low flow with the CHPM method. Volumetric water use determined with the dual heat-pulse sensors was highly correlated with hourly lysimeter water use in both years (R2=0.92 and 0.94 in 2008 and 2009 respectively), but the nature of the relationship was inconsistent among replicate sensors. Similar results were obtained when comparing grapevine water use determined from sap-flow sensors to miniaturised weighing lysimetry of 2-year-old potted vines and to meteorological estimates for field-grown vines in two additional vineyards. The robust nature of all of the correlations demonstrates that the dual heat-pulse sensors can be used to effectively track relative changes in plant water use, but variability of flow around stems makes it difficult to accurately convert to sap-flow volumes.

The effect of paclobutrazol injected into the soil on vegetative growth and yield of Vitis vinifera L., cv. Thompson Seedless

SummaryGrapevines, cv. Thompson Seedless were treated with the plant growth regulator paclobutrazol in the spring of 1984. The treatments consisted of four soil application rates (including a zero control) of paclobutrazol on two phenological dates (budbreak and bloom). Vegetative growth, as measured by pruning weight, vine yield and fruit maturity characteristics, were determined in 1984 and in the next three growing seasons. There was no significant difference in vine yield between treatments at harvest in 1984; however, the fruit of vines receiving paclobutrazol at budbreak had accumulated less sugar at that time. Paclobutrazol application significantly (P < 0.01 ) reduced pruning weights in 1984 for all vines receiving paclobutrazol. Only the highest rate of paclobutrazol significantly reduced pruning weights in 1985. The number of clusters per vine and yield were significantly less for the treated vines than for the control ones in 1985 and 1986. Pruning weights in 1986 and yield in 1987 showed no si...

Recovery of 15N-labeled Fertilizer by Thompson Seedless Grapevines: Effects of N Fertilizer Type and Irrigation Method

A study was conducted to determine the N fertilizer recovery efficiency (REN) of Vitis vinifera L. cv. Thompson Seedless grown in the San Joaquin Valley of California. Vines were drip- or furrow-irrigated and fertilized with 15N-labeled potassium nitrate (KNO3) or ammonium sulfate (NH4)2SO4. The fertilizers were applied shortly after anthesis with a single application of 25 g N/vine (~28 kg N/ha). An additional set of the drip-irrigated vines was fertilized 10 times beginning 20 April across a 20-week period during the growing season with labeled KNO3 (amounts equivalent to ~31 kg N/ha). Total biomass, N concentrations, and 15N of all vine organs, including the root system, were measured. There were no significant differences in REN (~40%) between the two fertilizer types (nitrate versus ammonium) for the drip-irrigated vines or for the comparison of a single application of KNO3 to a split application of that fertilizer applied every two weeks. The REN of furrow-irrigated vines was ~12%. The partitioning of 15N-labeled fertilizer taken up by the vine was significantly affected by fertilizer treatment. Approximately 47% of the ammonium fertilizer for the drip-irrigated vines was found in the clusters, while only 30% of the nitrate fertilizer for the split application of the fertilized, drip-irrigated vines was found in the clusters. The greatest amount of fertilizer N found in the roots was for the nitrate fertilized vines under drip-irrigation (both single and split applications). The results indicated that irrigation type greatly affected REN of the N fertilizers used in the study, and that irrigation and fertilizer type affected the distribution of N once it was taken up by the vine.

Recovery of 15N Labeled Fertilizer by Vitis vinifera L. cv. Cabernet Sauvignon: Effects of N Fertilizer Rates and Applied Water Amounts

A study was conducted to investigate the interaction of N fertilization rates and different irrigation amounts on N fertilizer recovery efficiency (REN) of Cabernet Sauvignon in a commercial vineyard near Oakville, California. The fertilizer treatments consisted of a control (no fertilizer) and two 15N labeled ammonium nitrate fertilizer applications (6.5 and 13.0 g N/vine). The N fertilizer was applied two weeks before anthesis. The irrigation treatments were various fractions (0.25, 0.5, and 1.0) of estimated vineyard water use (ETc), with the applied water amount for the 1.0 irrigation treatment from 7 Apr to 9 Sept equivalent to 312 mm. Midday leaf water potential (Ψl) was measured throughout the season to monitor vine water status. The labeled N fertilizer was detected in the petioles and leaf blades two weeks after application. Irrigation and fertilization treatments significantly affected midday Ψl. There were significant differences in aboveground vine biomass among the treatments. In general, those supplied with more water and/or N fertilizer had greater biomass compared with nonfertilized vines under deficit irrigation. Vine uptake of the 15N labeled fertilizer increased with increasing fertilization rates and irrigation amounts. The REN was significantly different between the two 15N fertilizer treatments (29% for 6.5 g N/vine and 24% for 13.0 g N/vine). REN at harvest for the 0.25, 0.5, and 1.0 ETc irrigation treatments was ~24, 28, and 27%, respectively, although not significantly different. The data indicate that fertilizer amount had a significant effect on REN under the conditions of this study and that irrigation rates at full ETc tended to increase REN in this vineyard when compared with deficit irrigation.