Vineyard Soil Moisture Check

Check Vineyard Soil Moisture 

Ashley Lipman, Horticultural Consultant, PIRSA Rural Solutions, Waikerie 

In 1994 many Riverland grape growers experienced poor grapevine development with uneven budburst and shoot growth, resulting in reduced productivity in their vineyards. These symptoms experienced by growers in 1994 were termed Restricted Spring Growth (RSG). It is not entirely clear what brought about RSG in 1994. One school of thought is that the warm dry conditions in the autumn followed by a cold, dry and frosty winter disrupted grapevine physiology.  

This reduced growth in spring resulted in substantial yield reductions in some vineyards. RSG in grapevines also occurred during 1982. The climatic conditions during these years appear to be very similar and RSG could again occur in vineyards in coming seasons.   

What to do?

As mentioned previously it is not exactly clear what causes RSG. During 1994 it appears those grape growers who maintained adequate soil moisture levels by irrigation during autumn, winter and budburst periods of 1994 had fewer problems associated with RSG. An examination of a cross section of vineyards throughout the Riverland recently showed that soil moisture levels were low, even with the application of a generous post harvest irrigation in April.

Grapevine water requirement is virtually nil during winter, however it is important that there is adequate moisture present in the soil to assist in raising soil temperature. Previous research and field data have shown that yield can be reduced by low soil moisture conditions at budburst. Growers who have not applied an irrigation during winter should consider applying a 25 to 40mm irrigation to simulate a rainfall event.

Growers who have applied irrigations during the winter period are advised to keep checking their soil moisture levels to ensure they have adequate moisture at budburst. 

A word of warning

Just as dry soil conditions may be damaging to grapevines so can excessively moist conditions. 

Care needs to be taken with spring irrigations to avoid over irrigation and the soil becoming too wet and poorly aerated. Soil temperature is often low at that time of year and limits root growth. When the soil is too wet, what feeder roots that exist can be rotted off, with stunted yellowing leaf growth occurring, particularly in calcareous soils. Regular checks of soil moisture combined with irrigation amounts which match soil type and crop water use should be employed to avoid the above scenario occurring. 

Frost 

The application of an irrigation will improve heat storage for frost protection at budburst. 

Vines are susceptible to frost damage from budburst to the end of October. Cover crops should be mulched or slashed down and light and frequent irrigation applied as necessary. 

In summary, grape growers who have not applied an irrigation during winter should check soil moisture levels and consider applying irrigation if warranted.

Summary of climatic conditions at Loxton during 1982, 1994 and 1999

 

1982

1994

1999

Mth

Evap.

Rainfall

Evap.

Rainfall

Evap.

Rainfall

 

mm/mth

mm/mth

mm/mth

mm/mth

mm/mth

mm/mth

Jan

276

9

276

-

330

5

Feb

219

1

197

19

223

23

Mar

172

17

200

-

181

27

Apr

99

18

127

3

120

5

May

60

11

98

-

83

31

Jun

43

14

48

41

52

10

July

55

3

60

14

56

31

Total

924

73

1006

77

1045

132
  • Long term annual average evaporation at Loxton 1,788mm
  • Long term annual average rainfall at Loxton 275mm

 

 

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