The application of gypsum and lime resulted in no significant increase in yields in this trial.
There were economic benefits with the application of 0.5t/ha ($7/ha) and 1t/ha ($20/ha) of gypsum and 1.75t/ha ($1/ha) of lime.

Background

Long-term soil amelioration trial sites have been established at the Alectown Regional site. These long-term sites are being monitored over five years. Below is a summary of the first year results at the sodic soil site.

METHODS

Location: Goonumbla

Cooperator: Richard and Roger Crisp

TRIAL HISTORY:

Date spread: 23rd April 2003 (treatment rates, commencement of trial)

Lime and Gypsum source: Bagged agricultural lime and gypsum

Sowing: 2003 5th July, Gairdner barley, 100kg MAP, 30kg urea

2001-2002: Pasture

Trial Design:

This trial is based on a randomised block design with six treatments consisting of one nil treatment, three gypsum treatments (0.5, 1 & 2.5 t/ha), two lime rates (0.7 & 1.75 t/ha) and one 50:50 lime/gypsum mix treatment (2.1t/ha) with two replicates.

Rainfall 2003

RESULTS

Soil Test Summary:

23 April 2003

YIELD AND ECONOMIC RESULTS:

Sodic soil amelioration trial results 2002

DISCUSSION

Soil Test Comments

Soil samples were collected at the beginning of the trial in April 2003. The soil test results indicated that the soil was had excessive amounts of Na and Mg and low Ca and therefore should show a response to gypsum.

Yield and Economic Response Comments

The differences between yields were not significant at the 5% level. This is consistent with trials carried out at Gunning Gap where significant yield effects were only seen after two years (Naughton et al., 2002). In both cases, this was most likely due the treatments needing more time to react in the soil, particularly as very little rainfall was received at Goonumbla after application. This trial was also affected by moisture stress and frost.

Although the statistical analysis could not show a significant yield impact at the 5% level, there were net economic benefits. 0.5t/ha and 1t/ha of gypsum showed a net benefit of $7 and $20 respectively. 1.75t/ha also showed a net benefit of $1/ha. 2.5t/ha of the gypsum/lime mix and 2.5t/ha of gypsum showed the least return. Initial outlay is a large expense, so the economic benefits of higher rates of gypsum may take a few more years to emerge.

The seasonal conditions in 2003 were highly unusual for the Parkes district, so it is recommended that farmers do not use this data in isolation when making decisions regarding soil amelioration. Continuation of the trial over the next 4 years will provide further economic and yield response data.

References

Naughton, M., Motley, K. and Rice, A. Sodic soil amelioration using lime and Gypsum. In Central West Farming Systems - Forbes & Parkes Regional Sites, Winter Crop Agronomy 2002 Trial Results. pp 8-11-19.

Acknowledgments

Richard and Roger Crisp (Trial Cooperator); Greg Gibson (Technical Assistance); Catherine Evans (Statistical Analysis); Central West Farming Systems, Grain Growers Association and GRDC (Funding).