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

The primary problem addressed in this project is how to develop new on-farm sources of organic material for New England vegetable farmers that are cost-effective, stimulate soil biological activity, supply plant-available nutrients, and build soil organic matter. In this study we examine the potential use of alder chips as a soil conditioner in intensive vegetable production systems. In the first year of a three-year rotation, we examined the growth and yield of two tomato varieties grown with ramial wood chips either incorporated into the soil or as mulch, in addition a treatment with incorporated chips made from leafy branches.

In this second year, another application of alder chips as a soil conditioner was continued on Peggy Rockefeller Farm. Prior to the spring growing season, soil samples for all 18 trial plots were pulled for basic soil tests. Alder branches less than 3” in diameter harvested in the previous year and fresh, spring alder with leaves were coarsely chip one week prior to the transplanting of Brussels sprouts. At the time of transplanting, all plants received pro-gro and crab meal. Based on the spring soil analyses, all treatments except for the compost control received sul-po-mag in order to compensate for the decline in potassium availability over the 2013 growing season. Over the 2014 growing season, we collected data on soils, growth (basal diameter), in row weed biomass, insect damage, and yield (total above ground biomass and weight of sprouts). Three presentations were given over the year, two in March for the Maine Vegetable and Fruit School (University of Maine Cooperative Extension) and one in the fall at the MOFGA farmer-to-farmer conference.  

Objectives/Performance Targets

The second year work plan focused on measuring cumulative impact of alder chip treatments on one of the two farms.   Experimental plots locations remained the same and last year’s tomatoes were followed up with a Brussels sprouts rotation. All transplants (Brussels sprouts var. Diablo) were started in the College of the Atlantic greenhouse in blocks of Fort V growing mix in late May and were potted up into 4-inch pots. Field transplanting occurred 28 June. Plant basal diameter was recorded twice during the growing season. Inter-row weed biomass and diversity were sampled mid-July and cumulative insect pressure was measured in the early fall. Final harvest occurred in mid-November prior to significant freezing temperatures. Total above ground biomass and total fresh weight of sprouts were measured for each of the 54 plants in the test plots.   The final rotation for this three-year study will be dry beans.

Accomplishments/Milestones

March 2014

“ Conditioning with woodchips” presentations to Maine Vegetable and Fruit School (Morse)

            Portland (100 registrants)

            Bangor (90 registrants)

May 2014

Re-hire student assistant: Polly McAdam

Soil sampling of last year treatments at Peggy Rockefeller Farm

Brussels sprouts started in COA greenhouse (Morse and McAdam)

June 2014

Field preparation, incorporation of alder and/or mulching (Morse and Walke)

Chipping of leafy alder

Transplanting

Irrigation and floating row cover

July 2014

Basal diameter measurements

Weed sampling and harvest

Remove floating row cover

August 2014

Weed sampling

September 2014

Sampling of imported cabbage butterfly damage with Entomology class (C Graham)

October to December 2014

Basal diameter measurements

Final harvest and weighing of sprouts

Presentation on use of alder chips at MOFGA farmer-to-farmer conference (CJ Walke)

Soil sampling

The average weight of Brussels sprout stalk was 5.5 lbs., with a range from 1.5 to 8.7 lbs. Sprout weight average across all treatments was 2 pounds per stalk and ranged from 1.0 – 3.56 pounds. The two mulch treatments had slightly lower yields. For the soils of this particular farm, there appears to be no negative within year effect on yield with the incorporation of alder chips and no evidence of nitrogen immobilization.   Soils analysis next year will focus on changes in both soil quality and nutrient changes under the 6 different treatments. The last crop within the rotation will be dry beans.

Between 2013 and 2014, weed biomass increased 3 fold in treatments without alder chip incorporation (compost control, no OM and alder mulch). The incorporation treatments had a minor 1.5 increase in biomass while the spring chip with fresh leaves, in contrast, had a significant decrease in weed biomass. The latter suggest that fresh ramial chips may have an allelopathic effect.

Cabbage white butterfly was a common visitor on the Brussels sprouts after the removal of the floating row cover at the end of July. In September, 17 students worked together to sample the top 5 inches of each stalk for the number of aphids (all 0), the number of cabbage white caterpillars, the total number of leaves in the top 5 inches and the number of leaves with any caterpillar damage.  A damage code was assigned to each plant to represent the severity of caterpillar damage: 0=no damage, 1= 25% of the leaf surface removed, 2=-50%, 3=75% of the leaf removed.  This code was a visually determined average of the leaves in the sample area (leaves coming from the top 5″ of stalk).   Overall, the percent of the top leaves with some damage ranged from 78 to 95 %, with the highest levels on the compost control and the spring alder chip. However, the extent of damage was more variable, with less than 25 % in the control and increasing across treatments, with the most in the spring alder chip with over 50%.  

Impacts and Contributions/Outcomes

Collaborators: