Impacts and comparisons of pruning and sanding on cranberry uprights and yield production

Final Report for ONE03-013

Project Type: Partnership
Funds awarded in 2003: $4,864.00
Projected End Date: 12/31/2007
Matching Non-Federal Funds: $6,500.00
Region: Northeast
State: Massachusetts
Project Leader:
Dr. Hilary Sandler
UMass Cranberry Station
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Project Information

Summary:

Six study beds were selected at a cranberry farm in Rochester (RCH), MA and in South Carver, MA. Six treatments were proposed: pruning + 0, 20, 40, or 60 lb/A nitrogen, sanding + 30 lb/A nitrogen, and no pruning + 30 lb/A nitrogen. Both sites received pruning and nitrogen treatments as proposed. The sanding treatment was originally planned for the winter of 2003-2004 without success, and then re-scheduled for three successive winters (2004-2006). However, the grower was unable to apply the sanding treatment. The sanding component was critical to the initial intent of the study. Due to these circumstances, it was decided to terminate the study in the fall of 2006. Although not intended as such, the data have been analyzed in the context of an annual pruning study using various nitrogen rates.

The weight of vines collected from the spring pruning event varied from 0.04 to 0.16 tons per acre; all N treatments yielded equivalent amounts of vines at each site in each year. Except for the occasional statistical difference, nitrogen rate plus pruning did not affect vine biomass and yield components, including flowering and vegetative upright density and biomass, runner biomass, total biomass, weight per berry, and marketable yield. In terms of total biomass, the 40 lb/A and 60 lb/A treatments produced more biomass than plots receiving less N in 2004 (RCH site) and 2005 (CVR site), respectively. All pruning treatments, even with high N rates added, had a loss of total biomass (which would be expected since they were pruned) compared to baseline data. Annual pruning with up to 60 lb N per acre did not adversely affect typical cranberry yield components. The inability of the grower to apply sand over the 4-year period of the project underscores the importance of identifying alternatives (such as mechanical pruning) for sand applications within commercial cranberry production.

Introduction:

An application of sand is a common horticultural practice in commercial cranberry production that involves the addition of up to one inch of sand to the production surface every 3 to 4 years. Sand is a non-renewable resource that is very expensive for growers to obtain and transport to their farms. It is estimated that sanding (including delivery, cost of material and labor to apply) can cost $2,000 or more per acre. Sanding has been described as a unique form of pruning. This has led local growers and researchers to ask, “Can mechanical pruning replace or reduce the need for sanding?” “Is the addition of fertilizer to pruned vines needed to maintain vine vigor and yield production?” To remain economically viable, cranberry growers need renewable, less expensive alternatives for their general horticultural practices.

This study, initiated by the concerns and interests of a cranberry grower, aimed to determine if pruning could be an adequate substitution for the traditional practice of sanding on a whole-farm demonstration-style basis. The goal was to compare mechanical pruning, with and without fertilizer, to the traditional cultural practice of sanding. The treatments were implemented by the grower using typical commercial machinery and practices. The demonstration plots can provide reliable information on the impact and influence of cultural practices on the productivity of the cranberry vines.

Project Objectives:
  • Comparison of sanding (common practice) and annual mechanical pruning (less common practice) as horticultural practices to increase cranberry vine vigor and improve canopy architecture.

    Determine if pruning has any negative impacts on yield or general plant health.

    Evaluate interaction of pruning and various nitrogen management plans on cranberry productivity.

Research

Materials and methods:

In Spring 2003, 6 study beds were identified at one site in Rochester (RCH), MA and one site in South Carver, MA. The study was designed as a demonstration-style experiment and was not replicated. Six adjacent sections (separated by drainage ditches) were used at each site. Treatments were randomly assigned to each section. When data were collected (except if noted differently), four subsamples (vines or fruit) were taken from each section. All data were collected in this fashion, analyzed, and averaged for presentation.

A motorized mechanical pruner with a retrofitted hay baler rotating head was used to prune the vines. The head was 6 feet wide and fitted with small, evenly spaced knives. The pruner is used by the grower to prune vines on the farm as part of typical farm operations. In 2003, the prunings generated from one 100-foot swath were collected and weighed (Table 1). To better account for variation in the vine cover, in subsequent years, four 50-foot swaths were used to estimate the weight of prunings generated (Table 1).

The original six treatments were: annual pruning + 0, 20, 40, or 60 lb/A nitrogen, sanding + 30 lb/A nitrogen, and no pruning + 30 lb/A nitrogen. The sites received pruning and nitrogen treatments in 2003; no sand was applied in the first winter. Unfortunately, the site in South Carver was eliminated from the study at the end of the first year since the grower decided to renovate the site due to poison ivy infestations. Another site in South Carver (CVR) was selected in 2004 and five of the 6 treatments were applied to both RCH and the new CVR site in 2004. The sanding treatment was planned for each subsequent winter (2004-2006). However, the grower was unable to apply the sanding treatment in any year of the study.

Upright samples (for vine density) were collected from RCH in 2003-2005 and from CVR in 2004-2005. Sample collection dates were as follows: April 24, 2003 (baseline sampling date for RCH); August 13, 2003, August 11, 2004, and August 23, 2005; April 21, 2004 (baseline sampling date for CVR), August 10, 2004, and September 8, 2005. Although sanding was planned for the winter of 2006, when this was not accomplished, no additional samples were collected (see below PI communication with SARE).
Vine samples were collected annually by cutting all uprights close to the bog surface within a selected area. Sampling templates were made by cutting 6-inch diameter PVC pipe into 1-inch wide bands. The sampling ring was randomly placed on the bog and positioned as close to the bog surface as possible. Using conventional hand clippers, cuts were made around the entire inner perimeter of the ring. The uprights were then held together and clipped as close as possible to the bog surface. The samples were placed into small resealable plastic bags and transferred to the freezer for storage at -20 C until evaluations were performed. Upon evaluation, the number of vegetative and flowering uprights and runners were separated into groups and counted. All plant material was dried for at least 48 hr at 105 C and then weighed.

Four areas were harvested for fruit in September each year. A 1-foot square area was selected randomly for each subsample, and all berries within this area were collected. The fruit were stored at 5 C in paper bags and visually evaluated for field rot within 1 wk. To approximate the size of berries collected during commercial harvesting, very small fruit were removed prior to evaluation. The samples were passed over a 5.6-mm sieve to eliminate nonpollinated, undersized, and aborted fruit. Fruit were categorized and counted as healthy, rotted or damaged. Healthy berries were then weighed as a whole sample.

Research results and discussion:

Treatment effects must be interpreted carefully as one of the (main) treatments (sanding) was never performed (see Tables 1-7). The study was not originally designed to evaluate the effect of N rate and annual pruning, but after consultation with SARE, it was decided to analyze the data in the most positive light, in spite of the omission of the sanding treatment. Various treatment effects were noted in a few of the measured variables (Table 1-6), but overall, no negative effects of pruning were noted. Treatment effects on yield were also variable, but overall, nitrogen had a minimal negative effect on yield. Pruning did not seem to adversely affect yield production.

No sustained or strong treatments effects were seen for either site in any year. Specific treatment effects include the 40 lb treatment has more (vegetative) biomass than the other treatments at RCH in 2004; the 60 lb treatment had higher numbers of flowering uprights than three of the four treatments in 2005 (Table 2). The unpruned treatment had more vegetative uprights than the 20 lb/A treatment at CVR in 2004; the 60 lb/A treatment generally had higher biomass than at least two of the other treatments in 2004 (Table 3). Calculations were performed to estimate the percentage change in biomass measurements relative to the baseline samples that were taken at the start of the study. Although numbers did vary, there were no treatment effects at either site in any year (Table 4 and 5). The pruning treatments showed a net loss in total biomass, which was not unexpected; the unpruned treatment stayed the same or increased. The pruning treatment receiving no N had larger fruit (both RCH and CVR) in 2004 than the untreated (Tables 6 and 7); no treatment effect was seen for marketable yield.

Accomplishments.
Demonstration beds were selected and monitored.
Treatments (pruning and nitrogen rates) were applied by the grower.
Baseline (spring, initial year only) and post-treatment (late summer) upright samples were collected from two sites by UMass research personnel in 2003 (1 site), 2004 and 2005 (two sites).
Fruit samples were collected in the early fall in 2003 (1 site), 2004 and 2005 (two sites).

The fist Carver site was dropped from the study in 2003. This is certainly an unfortunate event as we lost the opportunity to evaluate two sites for 3 years post-treatment. However, the dropped site was quite compromised by poison ivy infestation and the grower decided to renovate the area. The grower assigned a new site to the project in 2004. Three years of data have been collected for the RCH site and two years of data for the new CVR site.

Sanding was not accomplished in Year 2, Year 3, or Year 4 due to labor shortage, weather conditions and management choices on the grower’s part. The inability of the grower to apply sand over the 4-year period of the project underscores the importance of identifying alternatives (such a mechanical pruning) for sand applications within commercial cranberry production.

The PI contacted SARE (D. Holm) in November 2005 to discuss concerns with the “non-application” of the sanding treatment. The project was due to end December 31, 2005 and the inability of the grower to apply sand for several consecutive winters denied treatment comparison in accordance to the timeline and objectives established in the proposal. The goal of the project was to compare sanding vs. pruning for at least 1-2 years following the sanding treatment. Since this treatment did not occur during any of the four years (3 years + 1 no-cost extension year) of the study, it was decided (summer 2006) to terminate the study and to analyze 3 years of data from the Rochester site (2003-05) and 2 years of data from the South Carver site (2004-05).

The PI sincerely regrets the failure of the project to reach the goals initially established in the proposal. The PI appreciates the support and understanding that SARE has given throughout the course of the study and hopes that, given the constraints of the data, has appropriately addressed the original outcomes, accomplishments and outreach as outlined in the proposal.

Research conclusions:

Due to the expectation that the sanding would be accomplished in the “next” winter, outreach of the results of the study was not vigorously pursued. We kept hoping that we would get the sanding treatment included in the study. Since the sanding component was an integral part of the original study, its omission compromised the impacts and outcomes that would have been accomplished during the course of the study.

In an effort to pass on some gleaned information, a short report showing that annual pruning did not negatively impact yield components, irregardless of fertilizer regime, was published and circulated in the UMass Cranberry Station newsletter in August 2007 (http://www.umass.edu/cranberry/downloads/newsletters/aug07.pdf). The circulation for the newsletter is approximately 350 subscribers. The data will also be presented at the 2008 Growers’ Update Meeting in January, which is normally attended by approximately 250 growers. Information will also be placed on the UMass Cranberry Station web site as appropriate. The results of the study still have validity, but the reader and SARE should understand that results contained in this reporting are presented in an attempt to salvage some information from an experiment that never received an important treatment.

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary

Education/outreach description:

Potential Contributions. Although we never got the sanding comparison, this study showed that annual pruning under various fertilizer regimes had no adverse effects on typical cranberry yield components. Unfortunately, it also did not show any obvious benefit of annual pruning (within the context of our study). Since cranberries are biennial bearing, it is reasonable to assume that the study was not long enough in duration to demonstrate impacts.
A short report showing that annual pruning did not negatively impact yield components, regardless of fertilizer regime, was written and circulated in the UMass Cranberry Station newsletter in 2007. The circulation for the newsletter is approximately 350 subscribers. The data will also be presented at the 2008 Growers’ Update Meeting in January, which is normally attended by approximately 250 growers. Information will be incorporated into the UMass Cranberry Chart Book (Management guide) as appropriate.

Publications. This study was weakened by the omission of the sanding treatment. It is not anticipated that any specific publications or fact sheets will be generated from this study. Data and results have been published in the UMass Newsletter and can be downloaded at http://www.umass.edu/cranberry/downloads/newsletters/aug07.pdf. Interested parties can always check with the UMass Cranberry Station to see if the information has been incorporated into another fact sheet or similar.

Project Outcomes

Project outcomes:

Not applicable.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

Fortunately, SARE is currently funding a project that should provide more insight to this question of using mechanical pruning as a means to extend the interval between sanding events (PI, DeMoranville). This project has brought in several growers and also incorporates a replicated study conducted by a graduate student. Again, the inability of the grower to apply sand over the 4-year period of this project underscores the importance of identifying alternatives (such as mechanical pruning) for sand applications within commercial cranberry production.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.