Evaluation of the impact of modified storage practices on sprout suppression

At the time the research was comissioned, storage practices observed in North America (NA) differed markedly from those used in GB (and Western Europe). In particular, NA growers applied a lower amount of CIPC than was being used in GB and they tended to only make one application during the storage season. Over three storage seasons CIPC application trials were carried out in commercial bulk stores. Trials assessed a modified system, based on North American practices, and were compared with conventional CIPC applications in Great Britain.

The modified treatment consisted of continuous recirculation of the CIPC fog, through the bulk pile, with fans operating at low speed.  Air delivery to the pile was ‘balanced’ prior to application, to  deliver similar amounts of CIPC into all laterals. This was necessary because reductions in fan speed, from the normal operating range for ventilation, would otherwise have resulted in changes to the airflow dynamics of stores giving rise to uneven rates in different laterals.

Fog was generated with equipment modified (by close coupling) to reduce the volume of air/fog introduced to the store by around 35%, compared with a standard application. A solvent-free formulation was selected, which further reduced the volume of air/fog introduced to the store during application. Reductions in the volume of fog applied reduced losses of CIPC by limiting leakage as a result of displacement (i.e. volume in = volume out). Conventional treatments, for comparison, were carried out without recirculation of fog, with unmodified equipment and using a solvent-based CIPC formulation.

In all cases, the modified application procedure resulted in improvements. Improvements included enhanced sprout control efficacy, with reductions in mean maximum sprout length and sprout length variability, or an extension in storage duration. Improvements in sprout control efficacy were as a result of more even CIPC residue distributions and greater application efficacy.  Application efficiency (mean residue value expressed as a proportion of the application rate) for first treatments were found to be 30%, an improvement compared with literature values of 10%.  Second treatments resulted in application efficiencies of between c. 50-75%.

While sprout control efficacy was improved, the modified application procedure did not always result in reductions of CIPC input, and store design had an influence over this. In stores with a modest headspace (the volume of air contained in a store when it is loaded), applications were relatively efficient and input reductions were achieved. In stores with a large headspace, CIPC treatments did not result in significant residue levels and sprout control here was only achieved with relatively high CIPC use.

Overall, the modified application procedure represented an improvement in the use of CIPC and was promoted as best practice in bulk potato storage, whilst CIPC was available as a sprout suppressant (ie until Oct 2020).

To quantify the impact of modified CIPC application practices on the efficiency of application, eveness of residue distribution and sprout control