Over the last decade, grape growers in SE South Australia have had their water entitlements
converted to volumetric allocations, experienced a reduction in annual rainfall and seen a
rise in the salinity of groundwater which is used for irrigation. Irrigators have moved away
from flood and sprinkler irrigation, which was still widely used in the last decade of the 20
century, to precision irrigation applied with drippers. Annual application rates have decreased from between 4 and 6 ML/ha down to 2 or less ML/ha. In middle of the first
decade in the 21st century, salinity damage was emerging in some vineyards. In response the Limestone Coast Wine Industry Council convened a Root Zone Salinity Workshop in May 2006 at Padthaway. The current project addresses concerns raised following this workshop viz. ,
. characterising soil and vine salt status in vineyards affected by salinity
. developing techniques to more sustainably manage these vineyards
. extending knowledge about salinity management tools by supporting a salinity
monitoring network in the Limestone Coast Gl
. quantifying effects of long term precision irrigation with saline water on soil structure
Three salt affected vineyards were assessed at the close of the irrigation season in 2009 The high concentrations of sodium and/or chloride in leaves indicated that salinity was causing yield loss. Soils under the vine were saline and sodic with average values for salinity and ESP of 7.7 dS/in and 16%, respectively. However, soils in the mid-row were non-saline and non-sodic with average values for salinity and ESP of 0.6 dS/in and 4 16. Re- sampling at one of these sites after winter (365 min rain) showed that rainfall had Ieached soil salts and reduced sodicity with average under-vine values for salinity and ESP declining over winter from 9.3 to 2.5 dS/in and from 21 to 12%, respectively. In soils located under the vines in between drippers, the infiltration rate of rainwater was high, indicating that the high
ESP was not adversely affecting conductivity of these soils to low salinity water. However
indirect evidence points to reduced infiltration into the surface soil located nearer the
drippers. The soils under the vine were mounded and a reduction in infiltration would direct rain toward the mid-row. The flushing of soil salts by winter rain was not sufficient to bring
the salinity of soils to values below the threshold for salinity damage to vines. In part, this may reflect the persistence of a high ESP in deeper soils which may have limited drainage.
Under saline supplementary precision irrigation, the salts are added with the irrigation and the water to flush salt through the soil is provided by rain. The salinity of a soil is indicative of the balance between these two processes. Insufficient rain leads to salt build up and sufficient prevents it. Soils under the vines were saline, whereas those in the mid-row were non-saline. Rain reaching in mid-row soils was in excess of that required to prevent salinisation. Re-direction of this excess water to the soils under vine would reduce soil
salinity in this region provided that subsoil drainage rates were high enough to support the extra flushing. We hypothesised that changes in floor management which direct rain from the mid-row toward the soil under vine and which address high ESP in the soils at depth
under the vine, may assist in reducing salinity damage.
At the end of the irrigation season in the 2010, a trial was installed in a salt affected Chardonnay vineyard where soils from the mid-row had been mounded under the vine to a depth of about 0.2 in. The treatments consisted of a control(designated A), the removal of soil mounded under the vine (B), the application of calcium nitrate to 1 m wide strip of soil under the drip line (C), the covering of the mid-row with plastic to reduce losses from evapotranspiration (D), relocating the mounded soil under vine to the inid row and covering it
with plastic (E), and E combined with the application of calcium nitrate to 1 m wide strip of soil under the drip line (F). The trial ran for two seasons, 2011 and 2012 (year of harvest). Effects on soil salinity were assessed by measuring the salinity of the soil under the vine at the opening and close of the irrigation seasons. Measures of sodium and chloride concentration in leaves and fruit were used to asses the effect of treatments on vine salinity. The significances of different floor management regimes were tested with ANOVA and a set of contrasts.
Relative to salinity levels observed in vines and soils in the 2009 and 2010 seasons, those observed in the control, treatment A, during the trial were low, excepting soil salinity at the close of the 2012 season which had returned to pretrial levels. Low soil salinity in the control was not associated with variation in the depth of winter rain, but rather a variation in the depth of within season rain; when this was higher, irrigation depths were lower and hence so too was the annual saltload added to the vineyard.
Redirection of rain from the mid-row, treatments E and F, reduced the salinity of soils under the vine at the ends of the 2010 and 2011 seasons and at the openings of the 2011 and 2012 seasons; removal of the under vine mound, treatment B, reduced soil salinity at the end of the 2011 ahd the opening of the 2012 seasons. With in season rainfall in the 2012 season was low, less than a third of that in 2011 and just half of that in 2010. None of the treatments had an effect on the salinity of soil under the vine at the close of the 2012 season. At this time, the salinities of soils located at a quarter and half way across the row were also measured. In the control, treatment A, measurements of salinity and sodicity showed that the values had returned to the higher levels present at the end of the 2010 season
Redirection of rainfall(E and F) had increased the salinity of soils located at a quarter and half way across the row; addition of calcium nitrate (C and F) had increased the salinity of soils located half way across the row. The sodicity of deeper soil under the vine was measured at the close of the 2012 season. Redirection of rainfall(E and F) and addition of calcium nitrate (C and F) reduced soil sodicity by about 50%.
Measurements of salt concentration in plant organs represent an integration of salt pressure throughout organ development. In both seasons, redirection of rainfall(E and F) lowered leaf petiole sodium concentrations and leaf patiole and lainina chloride concentrations, and removing the under vine mound (B) lowered petiole chloride concentrations. In one of two seasons, covering the inid-row with plastic (D) reduced sodium and chloride concentrations, and removing the under vine mound (B) reduced petiole sodium and lainina chloride concentrations
In 2011. and 2012 seasons, redirecting rainfall (E and F) lowered sodium and chloride concentrations in the juice. In 2012, the concentrations of both ions were also reduced by removing the under vine mound.
Treatments did not affect yield. They caused smallreductions in juice 'Brix and increases in juice titratable acidity
Salinity monitoring sites were installed in a grower operated network at 14 sites across the Limestone Coast region before the 2010 season. The project staff provided each participant in the network with training and on-going support in sampling techniques. Sites were located in drip irrigated vineyards planted to Cabernet Sauvignon on own roots growing on mainly clay loam soils. Soil solution samplers were installed at each site at 0.3 and 0.6 in depth. Participants collected data on irrigation water and soil solution salinity, and rainfall depth and irrigation volumes. This data was cross related to measures of soil and vine salinity undertaken by project staff. Participants received biennial collations of all data and this
provided them the opportunity to benchmark their salinity measures against those of other network members. Soil solution salinity rose during the irrigation season and fell with winter rains. This readily obtainable measure of soil salinity did not provide a reliable basis upon which to predict either the standard measure of soil salinity (EC) or standard measures of vine salt status (sodium and chloride concentrations in petiole and juice). However, all measures of EC, below 3.5 dS/m had corresponding EC, values below the threshold of 2.1 dS/m for vine salinity damage and all measures of Econ above 7 dS/m had corresponding EC, measures above the threshold. In between these two values, there was a grey area where more conventional sampling techniques need to be applied to establish vineyards salinity status.
SARDl assessed the effect of a decade of saline irrigation on soil physical and chemical properties by comparing a set of current measurements of these properties with those made a decade ago at the same site by CSIRO Plant lndustry. Soils were sodic and saline in 1997 and again when measured in 2009; the salinity of soil in the top 0.6 in was 5.0 dS/m and the sodicity (ESP) was 13%. After, above average winter rain in 2011 the salinity of soils in top 0.6 in was 2.1 and the sodicity (ESP) was 7%. The sodic soils had been subjectto annual cycles of saline high SAR irrigation in summer and non-saline low SAR rain in winter over the previous decade. The return to non-saline and non-sodic state in 2011 indicates that any change in soil structure wrought by a decade of these cycles was not yet a significant impediment to Ieaching of salts and displacement of sodium from the clay eXchange sites. Comparison between two set of soil moisture release characteristics determined at either end of the decade showed they were different, however this may have been due to slight differences in the soil composition (5% gravel content in the earlier sample), rather than the effects of a decade of saline irrigation
Communication activities included: three journal papers, five conference papers, this final report, six steering committee meetings, three factsheets, seven workshops and seminars, and nine salinity monitoring network summary sheet mail outs.
