A presentation to a meeting of the Riverina branch of Soil Science Australia on 31 Aug 2018 by Sam North, NSW DPI, Deniliquin. CSIRO conducted soil surveys in the Deniboota Irrigation District in 1942 for soil mapping purposes prior to the introduction of irrigation. A small number of these sites were were re-sampled in 2017, with paired sites (irrigated & dryland) found on each soil type sampled. The results of the chemical analysis of the 2017 samples is compared with that from the 1942 survey. The major change appears to have been leaching of soluble salts (chloride) from both irrigated and dryland sites. It is postulated this is due to a wet period between 1950 and 1990.

1. The effect of 75 years of agriculture and
irrigation on soil condition in the
Deniboota Irrigation District
1942 to 2017
Sam North
NSW DPI, Deniliquin

2. • Aims
– Pilot study to
• compare laboratory analyses
• establish baseline soil health pre-irrigation
• assess long term affects of agriculture
• Methods
– digitise 1942 paper record for Murray surveys
– geo-locate 1942 sample sites - Deniboota ONLY
– re-sample a small set (24) of the 1942 sites - same depths
RBE TRBE NSMC
Dry Irrig Dry Irrig Dry Irrig
7 8 24-a 24 36 36-a
15 15-a 25 25-a 38 38-a
16 16-a 26-a 26 46-a 46
18-a 18 33 34 48-a 48

4. Clay % and ECEC (1)

5. Clay % and ECEC (2)

6. Clay % and ECEC (3)

7. pH (1)

8. pH (2)

9. Organic carbon (1)

10. Organic carbon (2)

11. Organic carbon (3)

12. TSS, EC and Cl

13. Chloride and Na (1)

14. Chloride and Na (2)

15. Chloride and Na (3)

16. Deniliquin landscape showing salt lake (1910-1930)

17. Deniliquin, 1910-1930

18. Deniliquin landscape – boree trees in middle ground (1910-1930)

20. Non-irrigated, native grasslandIrrigated, rice based farming system
An “across the fence” comparison – a sodic, grey vertosol