Developing a sustainable automated spring frost cycling protection method in cranberry production

Developing a sustainable automated spring frost cycling protection method in cranberry production

Summary

Cranberry frost protection is a necessary practice in the cranberry industry in order to avoid unnecessary losses through frost damage. An experiment was set up in South-east Massachusetts to investigate two of the common frost protection practices, conventional and automated intermittent irrigation. It was aimed at increasing the use of automated cycling irrigation by the cranberry growers, as this method is hypothesized to have significant water, fuel and environmental benefits, relative to the conventional method. The other objective was to assess the effectiveness of both methods in protecting buds against frost damage. This was done by evaluating cranberry buds collected from various beds protected by AI and conventional methods for bud damage. Those beds were then monitored throughout the season and parameters like flowering and fruit density analyzed for each method and water use also recorded with a flow meter. The cultivars Stevens, Howes and Early Black (EB) were used. There was 35% water savings from using AI with cycling. No notable differences were observed between the methods and cultivars when buds were assessed prior to the onset of frost protection, in the middle of the season and towards the end of the season. Minimal damage was observed across cultivars before the occurrence of frost nights. Although there was a trend of AI having higher bud damage than conventional, the differences were not significant, indicating that both methods are actually effective in frost control. The methods were also not significant for upright density count, berry count and even final yield. Instead, significant differences were found between cultivars. EB and Stevens both had an average of 45 flowering uprights while Howes only had 33 and EB had the highest number of uprights with two berries, while Stevens was the lowest. EB had the highest number of healthy and usable berries while Stevens had the lowest. The results imply that the yield is not impacted by use of either method in frost protection but mostly inherent cultivar differences.

Objectives/Performance Targets

The objectives of this project were to:

1. 1. Evaluate the efficacy of automated irrigation cycling for cranberry frost protection by assessing cranberry buds for frost damage following frost events across frost protection methods.

1. 1. Evaluate the effect of spring frost protection methods on plant density and fruit yield.

1. 1. Quantify the amount of water applied and fuel used during the evaluated cycling protocols for both mild and severe frost events and compare to water use in a non-cycled protocol.

1. 1. Synthesize the information gathered and distribute it to growers to encourage better water and land stewardship. 

To date, buds were collected for assessment from all the beds where AI and conventional frost protection methods were used. The progress of cranberry development was followed throughout the 2013 season until harvest time and included studying parameters such as: 

v  Water use

v  Bud damage

v  Flower count

v  Berry count

v  Yield estimate

Accomplishments/Milestones

In the spring of 2013, water use, bud damage during frost protection and overall performance of cranberries were studied in several commercial cranberry bogs in Massachusetts. One grower was not able to connect the flow meter to the pump, while the other only set it up when it was too late to take readings so the data for water usage throughout the season was only obtained from one grower. It was convenient in that both frost protection methods were confined within one geographic location, with similar environmental conditions. Three beds comprising of Early Black (EB), Howes and Stevens were selected under automated intermittent (AI), while only EB and Stevens were available under the conventional method. Similar cultivars were assessed for the rest of the sites. Flow meters (Image 1) were set up in April before the beginning of the season at each of the pumps supplying irrigation water to beds under each method. The flow meters accurately recorded the exact amount of water used and readings were taken after each frost event and recorded. Frost events were categorized into four groups (Table 1) across the season. Bud collection started prior to the beginning of the season, after the winter flood was drained from cranberry bogs, and continued after each frost event until the season was declared over by the Frost Alert Service in mid-June. Cranberry buds were systematically collected in different bogs by walking a transit across each bed and randomly collecting about 50 buds. These were dissected under a microscope (Image 2) for visual assessment of the extent or absence of damage and scored as follows:

1- healthy, bud interior bright green with floral initials, vegetative meristem and bud scales   

      intact

2- no damage in the vegetative meristem but some damage in one or two floral  meristems

3- bud damage in all floral meristems

4- bud damage in the vegetative meristem

5- bud completely dead with dark center and brown bud scales

 After the end of the frost season, the vines continued to be monitored and measurements for flower and berry count were taken within a 15.2 cm diameter ring (Image 3) placed randomly on the bed.

This evaluation process was repeated at three randomly selected locations on the same bed. Yield assessment was also made by collecting berries and sorting them out according to usable and rotted berries.

Results

Water Use

For the entire season, at the site where we had the flow meter recording water use, 477.3 gallons/acre of water were used for frost protection under conventional while 166.5 gallons/acre were used under AI. That means a total of 310.8 gallons/acre were saved by using AI combined with cycling, resulting in 35% water savings. These probably came about when the irrigation pumps under AI stopped running above the temperature threshold and cycled on and off while the conventional kept running even when it was not necessary. This is clearly one of the advantages of cycling versus non-cycling. These savings are significant and should be considered when choosing a frost protection method.

Bud damage

There were no significant differences between the cultivars and methods when buds were assessed prior to the beginning of the season. Minimal bud damage was observed under the conventional method, with the highest being only 6%, for Stevens (Fig 1). This implies that the winter flood which is applied on all bogs in the fall is effective in protecting the buds against frost damage throughout the winter season. As the season progressed, we observed generally higher bud damage, mostly under AI compared to conventional (Fig 2). Towards the end of the season, there were generally less frost nights and these were mild as temperatures were getting warmer. Again, the observed bud damage was low, with the highest being 5% (Fig 3) and there were no significant differences between the methods and cultivars, although there was still a trend of AI being higher than conventional. This will be repeated again in the 2014 season to confirm the results.

Upright density count

There were no significant differences between the two methods with regards to flowering uprights, but we found significant differences between cultivars (p<0.0056).  Although EB had high bud damage earlier, it was able to compensate, and  together with Stevens they both had an average of 45 flowering uprights while Howes only had 33 (Fig 4). Possibly, only one or two floral initials are damaged by the frost, thus being able to make up for that and still have a high number of flowering uprights later in the season.

 We also assessed the number of uprights with one, two and three berries and found all cultivars to have significantly the same number of uprights with vegetative growth and one berry for both methods. However, there was an interaction between method and cultivar (p=0.03) under two berries.

EB had the highest number of uprights with two berries, with an average of 14 while Stevens was the lowest, with an average of 9 (Fig 5). There is big decline between the number of flowering uprights and those that actually had berries. This is an indication that some flowers are aborted along the way or maybe succumb to disease and insect damage. However, yield does not seem to be influenced at all by any of the frost protection methods as we did not find any significant differences between the methods. Instead significant differences were observed between the cultivars (p=0.0066) with EB having the highest number of healthy and usable berries while Stevens had the lowest (Fig 6).

There were challenges obtaining data for fuel use primarily because of the way in which fuel is delivered to the tanks on cranberry bogs. Once the growers have signed the contract with the fuel supplier, the suppliers come in anytime to refill the tanks, making it difficult to account for what has been used. Moreover, there is no specific amount that they fill up to, just as long as there is enough fuel to run the pumps. These factors make it almost impossible to determine fuel use. In this coming season (2014), we will need to develop a different approach which will enable us to be successful in getting accurate fuel use results.

• a) McCrometer propeller flow meter connected to a pump engine b) A closer look at the flow meter
• Different levels of cranberry bud damage
• Dates for the 2013 frost season in South-eastern Massachusetts
• Shows the average number of uprights (flowering density) for three cultivars
• Average yield estimate (healthy berries) for three cultivars
• Average number of uprights with two berries for three cultivars
• Bud damage for three cultivars under two frost protection methods prior to the occurrence of the 2013 frost season
• Bud damage for three cultivars under two frost protection methods towards the end of the 2013 frost season
• Ring used for flower and berry count density
• Bud damage for three cultivars under two frost protection methods in the middle of the season

Impacts and Contributions/Outcomes

The project has only been done for one year and because of year-year variations, any impacts and contributions will be outlined at the end of the two year period, taking into account, the data for both the 2013 and 2014 seasons. This will also include publications and outreach. At the end of the study, growers will know how much fuel and water savings they are making by use of cycling irrigation, while also promoting environmental sustainability. Other growers will get an opportunity to re-evaluate their frost protection and management practices. In overall, there would be reduced tear and wear to the irrigation equipment, decreased water use, fuel consumption and its associated emissions.

Collaborators: