Technical Yearbook 2024

other treatments. The high extractable K + at all of the experimental sites is concerning as it could lead to greater K + uptake by grapevines, ultimately resulting in unstable wines with high pH. 23,26 In addition, high amounts of exchangeable K + have been associated with reduced K . 27,28 Soil extractable Na + followed similar trends as was observed for extractable sodium percentage (ESP´), therefore only ESP´ will be discussed. On average, the topsoil ESP´ increased by 1% and 3% for the SLD and DLD treatments, respectively. In contrast, the RF treatment was 3% lower compared to the baseline (Figure 5). A steady increase in ESP´ with depth was evident for all the irrigation treatments. This is probably due

ESP´ (%)

0

5

10

15

20

25

0 20 40 60 80

100 120 140 160 180

Baseline RF

Depth (cm)

SLD DLD

Figure. Effect of rainfed conditions (RF) and irrigation with treated municipal wastewater via single line (SLD) and double line drip (DLD) on the mean soil extractable sodium (ESP’) across main plots after 11 years of wastewater irrigation compared to the baseline before irrigation commenced (ARC, unpublished data). FIGURE 5. The effect of rainfed conditions (RF) and irrigation with treated municipal wastewater via single (SLD) and double dripper line (DLD) on the mean soil extractable sodium (ESP´) across the three different landscape positions after 11 years of wastewater irrigation compared to the baseline before irrigation commenced.

0 2 4 6 8

10 12 14 16 18

B

A

0-30 cm 30-60 cm 60-90 cm

0 2 4 6 8

50 100 150 200 250

-8 -6 -4 -2

ESP (%)

Change in ESP (%)

Y = -0.0802 + 13.87 (R 2 = 0.9206)

Rainfall (mm)

06 07 08 09 10 11 12 13 14 15 16

FIGURE 6. Temporal variation in ESP in the soil at bud break (A) and the effect of winter rainfall from May to September on the change in ESP´ (B), where vineyards near Philadelphia have been irrigated using treated municipal wastewater from the Potsdam wastewater treatment works. The encircled value was regarded as an outlier.

Cl - (mg/kg)

0

20

40

60

80

0 20 40 60 80

FIGURE 7. The effect of rainfed conditions (RF) and irrigation with treated municipal wastewater via single (SLD) and double dripper lines (DLD) on the mean soil chloride (Cl) content across the three different landscape positions after 11 years of treated municipal wastewater irrigation.

100 120 140 160 180

RF SLD DLD

Depth (cm)

31

TECHNICAL YEARBOOK 2024