Carrots: Practical evaluation of field storage alternatives


Project summary:
UK industry practice is to store carrots for winter / spring marketing in-situ, typically covered with a thick layer of straw (+/- polythene) to provide insulation against frost damage during the winter and to prevent warming and re-growth in the spring. However, the sustainability of field storage using straw (+/- polythene) is becoming increasingly challenged: due to the increasingly high cost and volatile supply of the large quantities of straw required; and also due to agronomic concerns such as nitrogen lock-up and weed issues. Consequently, carrot growers urgently need to examine and evaluate alternative options to current in-situ field storage practice. A previous project, (FV398a), identified inefficiencies (in terms of insulative value) in the current straw-based systems, some possible mis-conceptions, and alternative systems and materials that could have equivalent or better insulative value to the current system. However, estimates of insulative value of current and alternative systems were theoretical. This project will begin practical investigations of the current and alternative systems by (a) validation of the theoretical insulative values for alternative materials and their effect on crop quality and (b) investigate the requirements for practical implementation of alternative systems.
Benefits to industry:
The area of carrots stored under straw is estimated at around 3-4000ha per annum. Current (2013) estimates for the costs of straw-based field storage systems are around £30 per 500 kg Hesston bale (delivered to field), applied at 80-120 bales/ha. With application and removal included, the technique costs around £4000-5000 per ha on top of crop production and harvesting costs. This is a significant and annually increasing additional cost to production which growers have to bear – and which is not sufficiently reflected in additional returns from customers for stored carrots. However, almost as important as cost is the vulnerability of straw supply – particularly with the effects of changing climate on cereal straw production, but also due to the increasing demands on the available straw supply by other agricultural or energy sectors. In addition concerns by landowners about the role of straw in the import of long-term weed problems (particularly blackgrass) affects the availability of (new) land for production.
Theoretical calculations (in the previous project, FV 398a) of the insulation values indicate that a reduction in straw usage of up to 67% could be achievable by moving to a poly-over-straw system. This could amount to a saving of £2000 per ha, equivalent to at least £6 million per annum for the industry as a whole. Although the current costs of alternative materials may not lead to direct reduction in costs in the short term, there would be benefits in terms of being less reliant on a volatile supply of raw material and making additional land available where currently landowners are reluctant due to the risk of weed seed import.
Expected project outcomes
Validation of theoretical calculations for the insulation values of different field storage systems/materials in a range of environments. 
Information on the impact of different field storage systems on carrot quality at two harvest dates.
The above will enable growers to select alternative systems/materials with some confidence.
Information on the practical issues and engineering requirements that would affect the difficulty/ease of implementing alternative field-storage systems.
Field demonstration of the different systems.
Results from the project will be delivered back to growers through annual and final reports, field demonstration days, AHDB publications, dissemination at conferences and industry meetings as considered appropriate.
Project code:
FV 398B
01 August 2015 - 30 September 2017
AHDB Horticulture
AHDB sector cost:
Total project value:
Project leader:


FV 398b_GS_Final_2017 FV 398b_Report_Annual_2016 FV 398b_Report_Final_2017 Carrot field storage FV 398b_GS_Annual_2016

About this project

Project aim(s) and objective(s):
(i) Project aim(s):
Practical investigation of alternatives for field-storage of carrots
(ii) Project objective(s):
To validate the theoretical calculations of insulation value of different 'systems' obtained in FV 398a
To determine the potential and practical issues associated with the most feasible alternatives identified in FV 398a
To hold a grower demonstration day