Potential of coppiced alder as an on-farm source of fertility for vegetable production

Potential of coppiced alder as an on-farm source of fertility for vegetable production

Summary

This project evaluated on two farms the potential of chipped alder as an on-farm source of fertility for vegetable production.   Alder branches less than 3” in diameter were harvested in mid-winter and in early spring. The winter alder and spring alder were coarsely chipped two weeks prior to transplanting of tomatoes in mid-June. At the time of transplanting the tomatoes during the first growing season, all plants received 1/3 cup of pro-gro and crab meal.  The three organic matter treatments compared across both farms were control (crab meal and compost), no organic matter(crab meal alone), and alder (coarse ramial chips and crab meal).   Three additional alder treatments were implemented on one farm and evaluated the effect of mulching with alder, combining alder chip incorporation with mulching, and spring alder chip incorporation.  Drip irrigation and trellising were carried out per each grower´s standard.  We collected data on soils (nutrient and carbon content), growth (basal diameter), tissue nutrient content, in row weed biomass, and yield.  The first year´s data have been collected and are being analyzed.  Three presentations on the potential role of use of alder ramial wood chips and the experimental design were given over the summer and fall.

Objectives/Performance Targets

Alder branches were harvested from fence lines on PRF early in the winter of 2013 and stockpiled for processing at the time of transplanting.  Over 2 yards of coarse chips and less than one yard of coarse spring alder were chipped all in one day with a rented chipper.  All tomato plants were started in the College of the Atlantic greenhouse in Fort V growing mix on 8 May and transplanted into 4- inch peat pots 14 May. Daybreak (DBK) and Peggy Rockefeller (PRF) farms received transplants on 8 June and transplanted into the field on 21 June.  At the time of transplanting, Daybreak basal diameters were significantly larger (p=0.07 for Bellstar and p=0.002 for Orange blossom).  By the end of July, there was no difference between the two farms for orange blossom and belle star was significantly larger on PRF.   The last harvest for DBK was at the end of August with the onset of late blight in all treatments while the last harvest for PRF was the fifth of October. 

The experimental design was simplified in order to provide more powerful tests.  Treatment 1 with no additional organic matter (no OM) allows for a direct comparison of with and without compost while treatment three allows for a comparison of with and without alder.  Comparisons between 3 and 4 allows for test of the role of mulch with and without incorporated chips. While treatment five allows for a direct comparison of chips harvested in spring vs winter.  

The control for all treatments was based on tomato production practices used on COA’s vegetable farm (Beech Hill Farm) which includes pro-gro and crab meal at time of planting. 

Control:  compost          
Treatment 1:  no OM   
Treatment 2:  alder chip     
Treatment 3:  alder mulch
Treatment 4:  alder chip, alder mulch   
Treatment 5:  spring alder chip with leaves

Three growth estimates (basal diameter and height) were made between time of transplanting and the first harvest in August.  Fruit number and weight were followed from mid-August until the end of the growing season (early Sept for DBK and early October for PRF).

Accomplishments/Milestones

The majority of the planned activities occurred although the initial start date was delayed by nearly one month.  Changes in responsibilities and timing are indicated in parentheses after the time or activity. 

May 2013 (April 2013)
Hire student assistant:  Polly McAdam
Tomatoes started by Morse and McAdam in the COA greenhouse
Initial soil samples taken by Taylor at Daybreak and Walke at Peggy Rockefeller Farm
Soil duff collected from recently cleared forest, for mixing with chips (Morse)

June 2013 (May 2013)
Field preparation, treatments assigned, incorporation of alder and/or mulching, transplanting (McAdam, Taylor, Walke)
Chipping of spring at the time of transplanting (Walke)
Tissue samples analysis of transplants (Morse, McAdam)
Prior to planting, soil burst test, soil moisture (Morse, McAdam)
Photo-documentation of winter coppiced alder (no measurements on coppiced alder made)

July 2013
Disease and tissue census
Trellising
Deer fencing
Photo-documentation of coppiced alder on PRF (no measurements on coppiced alder made)
Tissue samples of tomatoes at time of flowering
Soil burst test 
Disease, tissue, and weed census
Tomato harvest, numbers and weights

August 2013
Disease, tissue, and weed census and harvest
Tomato harvest, numbers and weights
Present project at Eagle Hill seminar (Morse) and to Rockefeller family (McAdam)

September 2013
Disease, tissue, and weed census
Tomato harvest, numbers and weights

October to December 2013
Science symposium presentation (McAdam)
Soil burst test
Final harvest
Data analysis

One limitation of the project thus far is effective documentation of coppice growth.  All cut plants grew back vigorously but no biomass estimates were made prior to cutting that was done the previous winter in anticipation of the project. 

Impacts and Contributions/Outcomes

Initial harvests for DBK (8/13/13) were approximately one week earlier than PRF (8/20/13).  For both farm, end of August yields were not significantly different across treatments although yields of the compost treatment tended to be higher than all other treatments.

Final yields across all treatments on PRF (10/5/13) differed between varieties.  For Orange blossom, the compost treatment was significantly greater than all other treatments while there was no significant difference among alder treatments. Pounds of fruit per plant were highly variable, ranging from 2 to 35 pounds per plant.  For OB the compost treatment was significantly higher and the no OM treatment the lowest. For BS, all alder treatments were not significantly different and on average were 4 pounds lower than compost treatment (mean = 18 pounds per plant).  

Mulching had a notable effect on in-row weed biomass by mid-August.  The no OM treatments had the highest weed densities followed by the spring alder chip, incorporated chip, and compost.  Both mulch treatments had an order of magnitude fewer weeds.

Soil quality differences between farms and tissue analyses across treatments are still under analysis.

Collaborators: