SPOT: AL NO EJERCER LA OPCIÓN:

Due to the nature of this project, the selection of the studied sites was critical to ensure both vine and root growth variations were due to the soil resource. While high variation of both vine growth and soil type were readily observed within vineyards, differences in variety, clone, trellis or vineyard management excluded areas from inclusion. Therefore a meticulous set of selection criteria was established to minimise any environmental and cultural influences, as outlined below:

 own-rooted grapevines with same variety and clone;

 vines of same age, with vines being not younger than 5 years;

 identical row and vine spacing;

 identical soil management;

 identical canopy management, pruning and harvesting techniques; and

 located within a small geographical area to minimise mesoclimatic variation. Infra-red imagery of plant cell density (i.e. vine vigour) was used to identify vineyard variability when available, and to direct soil investigation within a vineyard.

Slope variations were more difficult to control as topography applies a strong influence on soil formation within Tasmania.

Plot location and layout

Using the constraints listed above, individual plots were located where changes in either plant growth or soil type were observed. Each plot consisted of one excavated soil trench per 12 vines as outlined in Figure 3. The soil trench was excavated parallel to the vine row and aimed to expose soil across two vines (i.e. the trench length was a minimum of twice the vine spacing). The trench was orientated parallel to the row and was excavated

at a minimum distance of 450 mm from the vine row. The profile face was gently cleaned by hand to a distance of 100 mm from the vine row to expose fresh soil before measurement of root distribution and penetration resistance.

Trench width varied between 600 – 800 mm and was less than half the inter-row space. Trench width varied between vineyards due to the availability of excavators however trench width was consistent between plots within the one vineyard. If any topographic variation existed, the soil trench was excavated on the lowest end of the plot to prevent water collection when the trench was open and to reduce the possibility of disturbed soil influencing nutrients (mixing), water infiltration and storage when the trench was re- filled.

Figure 3:Plot layout detailing location of the soil trench relative to the measured vines.

Observation of root distribution

Root distribution was determined during winter by using the profile wall method outlined by Bohm (1979). This method of recording root distribution was chosen over others as it was determined that it was the most efficient way of describing the distribution pattern. As grapevines are capable of exploring a large volume and have a low root density compared to other perennial plants. Prior to recording root distribution, the profile face was gently excavated back a further 100 mm by hand leaving the roots exposed. Root distribution of two vines were recorded and classified into four different size classes (< 1 mm, 1 – 2 mm, 2 – 5 mm, > 5 mm) using a 5 x 5 cm grid. Observations of root

Soil characterisation and sampling method

Detail field descriptions of each soil profile was undertaken as outlined by McDonaldet al(1990) and were classified according to the Australian Soil Classification (Isbell, 1996).

Soil was sampled for laboratory analysis by horizon boundaries. Samples were air-dried, the samples split with half ground to < 2 mm. All air dry soil was stored in air-tight zip lock bags.

Many profiles had large columnar primary structure that extended across horizon

boundaries. For consistency, these were mainly described as prisms throughout the lower horizons with only the upper most horizon described as a columns if a rounded top was present (Figure 4).

Figure 4:Diagram of soil structure description.

Penetration resistance

The measurement of penetration resistance was undertaken using a hand-held

penetrometer (Penetrometer ST 207, with 6 mm dia head) across the profile face same 5 cm x 5 cm grid used for recording root distribution. This allowed detailed observations

of soil structure and root growth to be compared to the soil penetration resistance. Penetration was measured on a freshly cleaned profile face to eliminate surface crusting of the soil.

Five measurements were taken for each cell of the grid to obtain an average cell value.

Estimation of plant available water

Plant available water (PAW) was calculated based on soil texture and used the conversion values of PAW (mm/cm of soil) outlined by White (2010) (see Table 2). Two PAW values were estimated. The first was calculated based on depth and was an estimation of PAW within the upper 1 m of the soil profile. The second calculation was based on observations of root frequency with the PAW value calculated for the soil depth that contained 90 % of all root observations.

Vine measurements

Yield and yield components

All the vines within each plot had fruit hand-harvested and individually weighed. Bunches were counted during harvesting to allow calculation of mean bunch weight per vine. The date of harvest was determined by each respective vineyard manager and all plots within one vineyard were harvested on the same day.

Pruning weight

Pruning weights were also assessed for each vine within the plots. Vines were pruned as per the standard vineyard practice which varied between vineyards (outlined in each individual methodology sections). Canes were counted prior to pruning and all pruned material less than two years of age was collected and weighed on electronic scales (resolution of 10 g). Mean cane weight was calculated by dividing the total pruning weight by the number of canes.

Remote sensing

Where available, images of plant cell density (PCD) were provided from the respective vineyard managers. These digital multispectral images were supplied by SpecTerra Services Pty Ltd (Leederville, Western Australia), using plant cell density (PCD) as the vegetation index. PCD is a ratio of reflected near infrared radiation (NIR) to reflected red radiation (R):

PCD = NIR/R (Dobrowski et al., 2002)

The near infrared waveband centred on 780 nm, and red light reflectance around 675nm. SpecTerra’s post processing involves the use of a proprietary algorithm designed to remove pixels that do not contain information from the vine row itself, eliminating interference from reflectance of the interrow surfaces. These images were used to quickly discriminate areas of high and low grapevine vigour.

Electromagnetic Induction

The sites were free surveyed for electromagnetic induction using a hand-held EM-38. Measurements were taken in both the vertical and horizontal diploe at each plot position. The location of each plot were recorded via a hand-held GPS (accuracy +/- 3 m, datum GDA94) and maps were produced using Surfer v.8 (software by Golden Software) by gridding the point data using kriging.

Soil chemistry

Soil samples were air-dried and then disaggregated using a mortar and pestle before passing through a 2 mm sieve. The fine fraction was then split sampled to ensure the analysed sample was homogeneous. All samples were initially analysed for pH (1:5 soil:water & 1:5 soil:CaCl2) and electrical conductivity (EC). The methods for

subsequent cation analysis were selected depending on these results as outlined in Figure 5. An outline of methods used is listed in Table 5. Soil samples taken for investigations on Tertiary sediments (Chapter 4) were stored before being sent to CSBP laboratories (Bibra Lakes, WA) for subsequent testing.

Table 5:Soil Laboratory Tests

Test Parameter Test Test Code References

Soil Reaction pH (1:5 soil:water) 4A1 Rayment and Higginson (1992) pH (1:5 soil:CaCl2) 4B2 Rayment and Higginson (1992)

Electrical Conductivity EC (1:5 soil:water) 3A1 Rayment and Higginson (1992) Exchangeable cations Ca

Mg See

Na Figure 5 Rayment and Higginson (1992)

K Al

ECEC derived

ESP derived