February (Maine Cranberry Management Calendar)

February: This is typically when Maine growers will apply sand (if needed). A 2006-2008 study out of Massachusetts has steered researchers there towards recommending that a good all-around canopy management strategy appears to be this: Sand every 5 to 6 years, with pruning in between. For the least impact on yield, the study found that whenever a ‘sanding’ or ‘pruning’ is done, it should be done on the light side (~half inch of sand in the case of sanding, and a single pass with the pruner in the case of pruning).

Summary of the Study:

Presented at the NACREW (North American Cranberry Research & Extension Workers Conference in Moncton, New Brunswick, Canada, in August of 2009)

“Sanding and Pruning Differentially Impact Cranberry Yield and Canopy Characteristics” – by Carolyn DeMoranville. The study was undertaken to see if pruning might allow Massachusetts growers to move away from sanding, at least in some years, or to use pruning alternately with sanding.

Some reasons why we sand and/or prune:

  • To prevent excessive vegetative growth (resource competition à lower yields);
  • To minimize/reduce shading;
  • To prevent fungal diseases

Sanding:

  • Increase in productivity;
  • Improved pest management – insects primarily;
  • Typically done every 2 to 5 years;
  • ½” is beneficial in the 2nd year following the sanding;
  • 1” is detrimental to yield but sometimes a good option for pest control;

Pruning:

  • 10% lower yield in 1st year, but a 45% increase the following year;
  • Can overcome sanding challenges/problems (sanding is expensive and there are uniformity issues);
  • Never before compared directly against sanding in a side-by-side fashion;

Study Design & Results:

  • Randomized Complete Block arranged in a Split-plot Design;
  • Sanding: Resulted in reduced leaf area (fewer uprights), and there was a carry-over to the 2nd year, too;
  • Light penetration is greater with sanding, initially, but after two years the light penetration amounts are equal between sanding versus pruning;
  • Leaf wetness: greater with pruning (compared to sanding);
  • Yield: negative impact on yield with sanding, especially if sanding heavy (1.5” or more);
  • TAcy: increased in pruning treatments only;

 Returns Per Acre with Pruning:

Initial Cost 2006 gross 2006 net 2007 gross 2007 net 2 yrs
net value
Control $0 $9,021 $5,821 $7,204 $3,904 $9,725
Light Pruning* $179 $13,592 $10,213 $9,309 $6,009 $16,222
Moderate Pruning* $885 $8,410 $4,852 $6,089 $2,789 $7,641
Heavy Pruning* $1,327 $6,870 $3,133 $6,675 $3,375 $6,508

*Light pruning = 1 pass with pruner; Moderate pruning = 2 passes; Heavy pruning = 3 passes;

Returns Per Acre with Sanding:

Initial Cost 2006 gross 2006 net 2007 gross 2007 net 2 yrs
net value
Control $0 $8,118 $4,918 $8,749 $5,449 $10,367
Light Sanding (1/2”) $3,190 $11,363 $6,872 $9,335 $6,035 $12,907
Moderate Sanding $5,965 $5,337 – $277 $4,431 $1,131 $854
Heavy Sanding (1.5”+) $8,734 $4,232 – $2,503 $2,621 – $679 – $3,182

Conclusions:

  • Light sanding or light pruning can be a useful tool for canopy management;
  • Sanding has greater risk (More expensive; heavier amounts are detrimental, even after the 2nd year following the sanding)
  • Resulting Recommendation Now Being Pitched to Massachusetts growers: Sand every 5 to 6 years, with pruning in between. 

One Last Important Point: Is mowing viable?  Answer appears to be Yes!  There is a big bounce-back in Year 3.