Investigating the effects of polyacrylamide in a commercial grade trial

Abstract

Several years of market volatility followed by drought had left the Riverland region precariously poised. The extent of the market depression and the drought caught many within the grape industry ill prepared and winegrape growers were left wanting for decision support tools and practical applications of science to assist their profitability under pressure.

Summary

A field test of polyacrylamide (PAM) amendment to commercial fertigation systems at two Riverland vineyard sites (Angove’s, Renmark and Centenary Orchards, Loxton), during 2008/09 aimed to:

• investigate the impact of PAM and its effects on vine performance in at least two commercial sized field trials (soil types);
• manage vineyard irrigation using PAM at critical water-use periods and make comparisons with standard management practices; and
• improve the technical aptitude of regional stakeholders with respect PAM and enable them to make informed decisions about its potential role in integrated irrigation and soil management systems

The treatments were applied PAM either as AG30, a more costly but easy to use formulation, or as AG60, a lower cost form lacking surfactants and emulsifiers.  At each site, vines and vineyards were monitored via weekly sap analysis, and assessment of yield and quality parameters, soil moisture, berry quality and canopy growth.

This extension project at both sites confirmed earlier published research and showed that PAM could play an important role in improving irrigation efficiency at a field level. The perceived impact of PAM on bunch elongation and increased fruit colour raises issues with regards to vineyard management and fruit composition that lay outside the scope of this study but which offer potential for further research at some future stage.

The outcomes from this trial indicated that the use of PAM (in either liquid or solid formulations) has potential to increase crop water use efficiency and decrease overall water requirements. The effect appears to be mostly through slower infiltration, greater lateral spread and lower percolation losses of irrigation water.

PAM treatment has the ability to reduce infiltration rates of irrigation water in light textured soils.  The treatment has potential to assist retention of soil water within root zones and reduce losses to drainage below the root zone.

PAM treatment, especially formulations like AG30 that include a surfactant, through its effect on soil aggregate stability, has potential to improve water infiltration rates into heavier clay based soils.