PRUEBAS

Ripping of wheel-line soils lowered petiole Na+ _{concentrations by 30% and Cl}- _{concentrations by 17% in} the 2015 vintage. In both the 2014 and 2015 vintages, values were well below the levels that are indicative of a salinity pressure sufficient to reduce yield (Robinson et al., 1997); 0.5% for Na+ _{and 1.5%} for Cl-_.

Petiole differences extended through to the expression of salts in the juice with ripped soils lowering juice Na+ _{concentrations by 11% in 2015 and Cl}- _{concentrations in both 2014 and 2015 vintages by 23} and 32% respectively. Lamina response was more variable with the greatest change being in 2015 where vines growing in ripped soils had 24% less Cl-_{, 0.36 against 0.47% (d.w.), Table 5.}

1.3.3.3

The effect of ripping compacted wheel lines on yield components

While soil response did not differentiate until the end of the 2014/15 irrigation season, yield components responded immediately. Shallow ripping of the compacted wheel-line saw an early change in yield with vines growing in ripped soils, Treatment A, producing 41% more fruit than those growing in the non-ripped soils, Treatment F, Table 6.

Soil salinity as EC_e (dS/m) 0 1 2 3 4 Dept h ( cm) -80 -60 -40 -20 0 A - Ripped Control F - Non-ripped Control

Table 5. The effect of shallow ripping soil in compacted wheel line, November 2012, on the expression of salts in leaf tissue (% d.w.) and juice (mg/L).

Parameter Treatment F

(Control plots adjacent to main trial area; zero soil disturbance)

Treatment A

(Control plots within main trial area; shallow ripping of wheel line)

LSD Petiole Na+ _{2014 0.296 0.330 0.05} Na+ _{2015 0.144 0.101}*** _0.02 Cl- _{2014 0.775 0.826 0.09} Cl- _{2015 0.684 0.571}*** _0.04 Lamina Na+ _{2014 0.149 0.130}** _0.01 §_Na+ _{2015 0.089 0.094 0.01} Cl- _{2014 0.503 0.469 0.04} Cl- _{2015 0.472 0.359}*** _0.04 Juice Na+ _{2014 28.5 28.6 2.30} Na+ _{2015 32.3 28.7}*** _1.82 §_Cl- _{2014 47.9 36.7}*** _2.59 Cl- _{2015 41.6 28.2}*** _2.38 † * <0.05, ** <0.01, *** <0.001 § geometric means

Table 6. The effect of shallow ripping soil in compacted wheel line, November 2012, on yield (kg/vine), bunch number (n/vine), berry weight (g), total soluble solids of juice (°Brix), juice pH and titratable acidity (TA g/L).

Parameter Treatment F

(Control plots adjacent to main trial area; zero soil disturbance)

Treatment A

(Control plots within main trial area; shallow ripping of wheel line)

LSD Yield 2014 2.89 4.81*** _0.67 §_{2015 2.25 2.87}* _0.47 Bunch No. 2014 76.9 110.3** _10.01 2015 32.3 51.1*** _7.03 Berry Wt. 2014 0.72 0.80* _0.04 2015 0.96 1.00* _0.04 °Brix 2014 23.61 22.93** _0.33 2015 26.71 25.64* _0.44 pH 2014 3.64 3.55** _0.05 2015 3.52 3.50 0.03 TA 2014 4.75 5.17** _0.21 2015 6.87 6.99 0.23 † * <0.05, ** <0.01, *** <0.001 § geometric means

This yield difference continued into the 2014/15 vintage, albeit less pronounced. Yield changes were reflected by higher bunch counts and bigger berries from vines growing on ripped soils. While higher yielding vines with bigger berries may not be in the interest of better quality wines, the effect also

comes with a delayed maturity, as indicated by sugar content, pH and titratable acidity, which may be of interest when considering winery intake logistics. Vintages are becoming increasingly compressed with varieties that once had distinctly different harvest dates beginning to overlap. Strategies to influence the timing of maturity, without compromising quality, are worth noting.

1.3.4

Effect of rainfall redirection treatments

Figure 13. Photos of rainfall harvesting treatments, A-ripped control; B-bare earthen mound; C- earthen mound with periodic application of surface crusting agent; D-plastic covered mid-row mound; E-buried plastic mid-row mound.

1.3.4.1

The effect of rainfall redirection treatments on soil salinity

Rainfall redirection treatments did not immediately influence the average profile salinity of the under- vine soils. However, by spring 2014, Treatment E saw a 23% reduction in under-vine salinity relative to Treatment A control plots, Table 7. Treatment D was also trending lower at this time but did not become strongly significant in its difference from Treatment A until after the 2014/15 irrigation season. In April 2015, both Treatments D and E were around 29% lower in average soil salinity compared to Treatment A. In April 2015, Treatment C was trending lower when analysed at a reduced sensitivity (P<0.1), but in the context of improvements demonstrated by Treatments D and E, and in the context of plant response data (sections 1.3.4.2), this trend becomes less noteworthy.

Figure 14 details the distribution of soil salinity with depth for each of the four time-steps described above. It includes data from the non-ripped controls, Treatment F, against Treatments A-E. Soil salinity traces highlighted how little difference there was between treatments until soils were exposed to the lower rainfall and higher irrigation volumes of the 2014/15 season.

Soils sampled in spring 2013 described the soil condition following the first full winter after treatment construction. At this point, there was no significant differentiation between treatments although Treatment F soils did express a slightly higher salinity bulge at 0.3 m. This bulge equated to a 35% greater salinity at 0.2-0.4 m relative to that of the surface soils and was a trend that did not occur in any other treatment. It is presumed that this was an artefact of the wheel-line ripping event that all other treatments were exposed to during treatment construction, see section 1.3.3.

Following the winter rains of 2013/14, Treatments D and E remained lower in their salinity than all other treatments. In spring 2014, this was most pronounced in the deeper soils where most other treatments expressed at least a 25% increase in salinity when moving from 0.4 m through to 0.8 m. The notable exception was Treatment B, which did not increase salinity in the deeper soils. It is difficult to explain why the salinity trace of Treatment C did not mirror that of Treatment B given their similarities in floor management and that the surface sealant in Treatment C would presumably increase fresh water reaching under-vine soils.

Table 7. The significance† of floor management treatment effects on the average profile salinity (expressed as ECe, dS/m) of under-vine soils sampled autumn and spring 2013/14 and 2014/15.

Sampling Date Treatment LSD A B C D E 22/11/2013§ _{1.21 1.27 1.21 1.07 1.15 0.25} 07/04/2014§ _{1.29 1.25 1.17 1.17 1.14 0.36} 14/11/2014§ _{1.22 1.23 1.21 0.99}* _0.94* _0.23 10/04/2015§ _{1.94 1.83 1.74 1.37}* _1.39* _0.38 † * <0.05, ** <0.01, *** <0.001 § geometric means

By the end of the 2014/15 irrigation season, average profile salinities of Treatments D and E were lower than those of all other treatments, and Treatments A-E were lower than the non-ripped Treatment F. In April 2015, following the 2014/15 irrigation season, additional samples were collected from mid-row soils in both the ripped and non-ripped control plots, Treatments A and F, as well as in the rainfall redirection treatments D and E. These soils were used to characterise the two-dimensional distribution of soil salinity across the row. Figure 15 shows that for each treatment, distance from the vine row, rather than depth, was the greatest source of variation.

Mid-row soils were between 60 and 70% lower in their salinity in the ripped and non-ripped control treatments and around 30% lower in the two rainfall redirection treatments. This trend is consistent with pre-trial measures collected from the site and also to those observed in another supplementary irrigation district, Padthaway SA, where a rainfall redirection proof of concept trial was conducted by Stevens et al. (2012).

Combining soil salinity data from both the under-vine and mid-row sampling points revealed that the non-ripped Treatment F had the greatest overall profile salinity at 1.85 dS/m. Treatment A, 1.5 dS/m, was 19% less saline than non-ripped plots and the rainfall redirection Treatments D, 1.25 dS/m, and E, 1.2 dS/m, were between 30 and 35% less saline than the non-ripped controls respectively.

Floor management effects on under-vine soils were significant, as has been described above. Effects on mid-row soils were more variable with rainfall redirection treatments appearing to show higher salinity at depth than control treatments.

Figure 14. The effect of vineyard floor treatment and sampling depth on soil salinity, prior to and following the 2013/14 and 2014/15 irrigation seasons.

ECe (dS/m)