Soil management for yield and quality Carolyn. L. Howell
Dean. M. Lanyon
South Australian Research & Development Institute (SARDI) GPO Box 397 Adelaide SA 5001
CSIRO Sustainable Ecosystems PMB2 Glen Osmond SA 5064
Michael. McCarthy SARDI GPO Box 397 Adelaide SA 5001
Introduction With water becoming an increasingly scarce resource, vineyard management practices that reduce water requirements of grapevines are required. Many Australian vineyards have potentially restrictive rootzones which leads to inefficient water use. This inefficiency can impact on vine performance, irrigation requirement and soil sustainability. Whilst the use of surface mulches along the vine row and management of the mid row to increase water availability to the vine has received increased attention (e.g. Buckerfield and Webster 2002; Lanyon and Bramley 2004; Lanyon et. al. 2004) information that provides vineyard managers with the magnitude of vine response to different soil management practices is not available for a range of soils. Therefore, research is presently being conducted by the South Australian Research & Development Institute (SARDI) and CSIRO in South Australia's McLaren Vale and Nuriootpa regions to determine the effect of soil profile modifications and under-vine surface management on vine performance. This research is one of three objectives of the Soil Management for Yield and Quality project which is part of the wider Grape and Wine Research and Development Corporation (GWRDC) Soil and Water initiative project. Even though the project has been conducted for one season only, some trends have already been observed and are reported here. McLaren Vale trial The aim of the trial at McLaren Vale is to determine the interaction between root volume, physical amelioration of soil and under-vine soil surface management on soil water availability and grapevine yield and quality across a range of soil types. Four different soil types were identified in a Cabernet Sauvignon vineyard in the McLaren Vale area. These soil types are: clay loam over a medium clay (SI), sandy clay loam over a medium clay (S2), light sandy clay loam over a light clay (S3) and loamy sand over a light sandy clay loam (S4). A mulch and a ripping treatment was applied to each soil type and is being compared to normal soil management practices. In the 2006/2007 season, berry growth and ripening was monitored from veraison to harvest. About 100 berries were sampled at each plot, weighed and mass per berry determined. Sugar, acid and pH of the grape juice were measured. At harvest, number of bunches and yield from each grapevine was quantified. Results The effect of soil type had a larger impact on berry growth and maturity than the effect of soil management. At veraison, berries of SI and S2 were significantly heavier than S3 and S4 berries (Figure 1A). Prior to harvest and at harvest, berries of S4 were significantly heavier than the other berries. At veraison, berries from ripped treatments were significantly heavier than berries from control and
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mulched treatments. At harvest, berries from ripped treatments tended to be heavier than the other berries. Similarly, berries from S3 and S4 had significantly lower sugar at veraison than berries from SI and S2 (Figure IB). Throughout the monitoring period, berries from S4 had the lowest sugar content. At harvest, sugar content of S4 berries was significantly lower than that of SI, S2 and S3 berries. Control, mulch and ripped treatments did not affect sugar accumulation of berries. Titratable acidity ranged from about 41g/L to approximately 16g/L at veraison. Throughout the season, S4 had the highest titratable acidity (Figure 1C). Similarly, pH of berries from S4 was consistently lower than that of SI, S2 and S3. Control, mulch and ripped treatments did not significantly affect titratable acidity of berries throughout the season. But, at harvest, mulch treatments had significantly higher acidity than berries from the control. Yield of all the treatments ranged from just under 1.5kg/vine for control vines on SI soil to almost 3.5kg/vine for the ripped treatments on S4 (Figure 2). Grapevines from S4 yielded significantly higher than on the other soil types which can be attributed to significantly bigger bunches. In contrast, the smallest bunches were obtained from SI grapevines. This was reflected in production with SI yielding the least and S4 yielding the most. The effect of soil management on yield showed that the ripped treatments tended to produce higher yields than the control treatments across all soil types, however, this could not be supported statistically. Nuriootpa trial The aim of the study at Nuriootpa is to investigate the effect of inter-row subsoil amelioration and post amelioration management on vine performance as a means of overcoming soil compaction and retarded root growth into the mid row. The trial is being conducted at the SARDI Nuriootpa Viticulture Centre so that traffic, which can cause recompaction, can be controlled. The trial has been arranged as a complete block design with restricted randomisation comprising four treatments, namely ripped plus traffic (RT), ripped plus no traffic (RNT), non ripped plus traffic (NRT) and non ripped plus no traffic (NRNT). Measurements taken were as described for the McLaren Vale treatment. Results The effect of ripping had a larger impact on berry growth and maturity than the effect of traffic. At veraison berries from both RT and RNT were significantly smaller than berries from NRT and NRNT treatments and this pattern continued to harvest (Figure 3A). At harvest differences were not statistically significant. Grapevines subjected to no traffic on rows tended to yield heavier berries than grapevines with traffic. Sugar concentration of NRT berries was consistently highest whilst that of RNT berries consistently the lowest (Figure 3B). At
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10 15 20 25 Days after veraison
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Fig. 1. Effect of soil type on (A) berry growth, (B) sugar accumulation, (C) titratable acidity and (D) pH of Cabernet Sauvignon grapevines as measured from veraison at McLaren Vale during the 2006/07 season. Vertical bars indicate least significant differences (P< 0.05).
harvest, sugar concentration of berries growing on unripped soil was significantly higher than that of berries from grapevines growing on ripped soil. At harvest, pH of NRT was significantly higher than the other treatments (Figure 3D). The pH of berries from grapevines with traffic was generally higher than that of grapevines from non
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soil management
S1C
S1M
S1R
S2C
S2M
S2R
S3C
S3M
S3R
S4C
S4M
S4R
RT
NRT
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Fig. 2. Effect of soil type and management practices on production of Cabernet Sauvignon grapevines as determined at harvest. Bars followed by the same letter are not significantly different (P< 0.05).
Fig. 4. Effect of vineyard traffic and soil management practices on production of Shiraz grapevines as determined at harvest. Bars followed by the same letter are not significantly different (P< 0.05).
traffic rows. At harvest, titratable acidity of NTNR was significantly higher than the other treatments (Figure 3C). In this first year of the trial, production results were quite dramatic (Figure 4). The overall low yields and possibly the scale of variation between treatments can be attributed to the severe drought in South Australia and are not expected in following years of the study. Yield of NRT and NRNT grapevines were more than double that of RT and RNT. Biggest bunches were obtained from grapevines growing on unripped soil. Bunches were almost double the size of their ripped counterparts. Post-ripping traffic did not affect bunch mass, yield and number of bunches per vine.
Preliminary conclusions From these preliminary results, it seems that in the McLaren Vale trial, soil type had a greater influence on berry growth, ripening and yield than the mulch and ripped treatments applied. Further, the trial at Nuriootpa seems to indicate a decrease in vine function caused by the combination of drought conditions and root pruning. Results from both trials are in contrast to the results obtained by Lanyon and Bramley (2004). They showed significant increase in yield for both mulch application and ripping of the mid-row as a function of surface soil type. But both trials will be conducted for another two years to quantify longer term responses. With the inclusion
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4.0
3.5
a 3.0
2.5 10
15
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25
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Days after veraison Fig. 3. Effect of vineyard traffic and soil management practices on (A) berry growth, (B) sugar accumulation, (C) titratable acidity and (D) pH of Shiraz grapevines as measured from veraison at Nuriootpa during the 2006/07 season. Vertical bars indicate least significant differences (P< 0.05).
of results along with results from previous trials, this study will culminate in guidelines for soil management practices that consider differences in soil texture and maximise stored water in the soil to increase yield and quality of grapes. Whilst these guidelines will remain general in nature with respect to grape variety, it is envisaged that they will become more robust and variety specific as more information becomes available.
Foster's Wine Estates, as well as staff at the Nuriootpa Viticulture Centre is gratefully acknowledged.
Lanyon DM and Bramley RGV. 2004. Ameliorating soil constraints to the performance of established vineyards, GWDC Final Report: Project No. CSL01/01, CSIRO Land and Water / Grape and Wine Research and Development Corporation, Adelaide.
References
Lanyon DM, Cass A and Hansen D. 2004. The effect of soil properties on vine performance, Technical Report No. 34/04, CSIRO Land and Water, Adelaide
Buckerfield JC and Webster KA, 2002, Organic matter management in vineyards - mulches for soil management, The Australian & New Zealand Grapegrower & Winemaker, 461:26-33
For further correspondence contact, Dean Lanyon of CSIRO at dean.lanyon@csiro. au, tel +618 8303 8746, Mike McCarthy at
[email protected], tel +618 8568 6400 Acknowledgements
This work was funded by SARDI, CSIRO, Fosters Wine Estates, and Australia's grapegrowers and winemakers through their investment body, the Grape and Wine Research and Development Corporation. Support from the latter was matched by the Federal Government. The assistance of David Hansen and David Williams of
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