Comparing Season Extension Mechanisms on Winter Green Production in the Southern Appalachian Mountains

Comparing Season Extension Mechanisms on Winter Green Production in the Southern Appalachian Mountains

Summary

A trial of winter salad greens was conducted at Ivy Creek Family Farm to evaluate the cost/benefit advantages of three season extension mechanisms.  Four types of greens were trialled in this experiment (Flamingo Spinach, Tyee Spinach, Asian Brassica Mix, and Salanova Lettuce), and were harvested in timed trials over a six month period ranging from September-February.

Objectives/Performance Targets

With support from SARE, we were able to quantify the cost/benefit return per bed foot of each season extension mechanism we trialled on each of the three greens.  Results for the project will be measured by the yield per plot and evaluated based on mechanism yields, crop variety yields, and the labor/yield of each crop.  Yields harvests will be done every two weeks once the crop is at a harvestable stage and timed to understand how much labor each crop takes to harvest. Plots yields will be weighed pre-washed to determine the harvest weight to the 100th/pound.  We hope to gain empirical data that will help inform and shape the planning, sowing, and harvesting techniques of salad greens during the fall, winter, and early spring growing season.

Accomplishments/Milestones

We propose to trial the performance of three season extension mechanisms on three in demand salad greens – spinach (arrow-leaf and savoy), lettuce mix, and braising mix.  We aim to quantify the cost/benefit return per bed foot of each season extension mechanism.  Mapping this information on an experimental scale will help our farm and others to invest in the appropriate growing techniques and labor requirements for producing winter salad greens to meet the fresh market demands of the Southern Appalachian Mountains.  We also anticipate increased market sales of storage crops such as sweet potatoes, potatoes, winter squash, rutabaga, onions, and carrots when displayed next to salad greens.   We also believe that a consistent selection of fresh produce will open customers eyes to less established winter salad greens such as mache and claytonia.

The treatment factorial is:

Season extension structure: 3
Winter green varieties: 4
replications: 4
3x6x3
total plots: 36                 12 in each season extension structure

with 2 planting dates: 72 plots, 24 in each structure.  

Experimental design layout:

This project will investigate the production of winter salad greens under different season extension structures commonly used by direct market vegetable farmers.  Three season extension structures will be trailed: a size 25’ x 75’  stationary high tunnel w/ roll up sides with beds protected in a non permanent 3’ tall x 5’ wide low-tunnel using 0.9oz weight floating agribon rowcover , a non permanent 3’ tall x 5’ wide polyethylene covered low-tunnel, and a non permanent 3’ tall x 5’ wide low-tunnel using 0.9oz weight floating agribon rowcover.  Three types of winter salad greens will be evaluated; lettuce, spinach, and an asian brassica mix.  Two cultivars of spinach (Tyee and Flamingo), a lettuce mix (Salanova Premier Collection), and one asian brassica mix (Braising Mix) will be used.  We will replicate the trial using two sowing dates, Set. 15th and October 15th. Plots will consist of one 5’ foot long section of a 42-inch wide, 6 inch tall bare-ground raised bed.  Plants will be transplanted into the growing beds using 3 rows spaced 12” apart and 6” in-row spacing.  The total row feet of each crop will be 60’ per trial date per mechanism. Three replications of each treatment combination will be installed in each season extension structure in a randomized complete block design.  

Results for the project will be measured in yield per plot. Yields harvests will be done every two weeks once the crop is at a harvestable stage.  Plots yields will be weighed pre-washed to determine the harvest weight to the 100th/pound.

In an effort to achieve the most uniform and unbiased data, all of the salad greens grown for this trial were seeded in the same sized cell trays (128’s).  All varieties of greens were seeded in our propagation house on the same day for each of our two trial starting dates.  All varieties were transplanted with careful attention to achieve the exact same plant density per bed food (6”in row spacing).  

The same harvest knife (Victorinox serrated harvest knife) was used to harvest the crops in this experiment.  Each crop had its own specific harvesting technique, a variable that affected harvest times and informed conclusions for future harvest protocols on our farm (both spinach varieties were harvested by the leaf, the Asian braising mix was harvested by the clump, and the Salanova lettuce heads were harvested by the head).  All harvests times were recorded using a stopwatch.

We used ½” EMT metal conduit tubes formed with a tool purchased from Johnny’s Seeds to support row covers and poly film.  These sturdy arched supports allowed us to maintain a uniform volume of protected/improved environment for the trialled plants to grow within.  We attempted to use the same mechanisms for holding the floating row cover and the poly film to the EMT hoops, but discovered quickly that extreme fall winds overpowered the weighted sandbags and the plastic friction clips trialled.  We abandoned the former mechanisms in favor weighing down the row cover and film with soil shoveled from the wheel tracks between the beds.

Impacts and Contributions/Outcomes

On October 11th 2014, we invited the public and members of the WNC C.R.A.F.T. chapter to our farm to discuss our experimental trials.  We covered topics including why we were conducting a cost/benefit based season extension trial, the mechanisms we were using in the trial, our thoughts behind the crop selections in our trial, and explanations on why increasing farm sales during the winter months is such an important strategy to the small mountain farmer.  This dialog took place around the various trial plots in our experiment.  During the seven-month length of this experiment, we trained four of our apprentices on the techniques used to collect data for on farm trials and often asked for them to reflect upon the data we were gathering.  This feedback was invaluable to understanding the aspects of our trial that are difficult to quantify.  

The most common feedback from apprentices involved in this project centered around the added labor demands of recording data and setting up an unbiased trial.  The reality of added labor demands was tempered by the common goal of collecting such powerful and precise data.  Everyone who participated in the trials tried to come up with solutions for keeping the poly-film from blowing away in the strong winds of autumn and winter.  Most felt that the likelihood of wind blowing the poly-film off of the bed or rain causing destructive ponding between EMT supports did not outweigh gains of its season extension properties.  Everyone involved in the production and harvesting of the trials enjoyed the work environment of the stationary high tunnel far above working on the trials being conducted in the field.

We have included a table of the raw data collected during this trial for review by the agricultural community. (Disclaimer:  Data of harvest times is skewed by the design of experimental plot design.  Actual harvest times for these crops is less than our data reflects).  After evaluating this data, we have come to the following conclusions.  

At the suggestion of Tom Elmore of Thatchmore Farm, we decided the beds covered with floating row cover in the fields should be treated as our control for comparing the three different season extension techniques.  We could have planted an unprotected control, but did not feel like it was worth the time to plant and record yields of damage crops.  The poly-film covered beds produced on average a 12% higher yield than the control.  The beds inside of the stationary high tunnel protected by floating row cover out produced the control beds by 163%.  As stated earlier in the report, all aspects of growing, cultivating, irrigating, pest management, and harvesting were greatly improved in the crops grown in the stationary high tunnel under beds protected by floating row cover.

As we compared the total yields per dollar of each crop within the trial, we noted that Tyee Spinach was the lowest performing crop that we trialled.  The arrow-leafed spinach variety Flamingo generated 16% more dollars over the course of the experiment.  Our asian brassica braising mix generated 29% more income than the Tyee Spinach.  The crop that generated the most sales was our Salanova lettuce trials, generating 39% more dollars than the Tyee Spinach.  Sales figures in this trial were generated on current wholesale prices and are not intended to be exact.  It is interesting to note that the only crop that we actually sold 100% of during the experiment were the two spinach varieties.  Lettuce sales were closer to 90% during this time of year, while we only sold 40% of the braising greens we were producing.  To correct this issue for future season extension crops, we would work harder to created market interest for the braising greens before we planted the crop and allocate more bed space to meet the spinach and lettuce demand.

The last comparison of our data provided the most unexpected of our trials.  As our apprentices move onto their next endeavors in the winter months, our farm is left with a labor shortage.  For this reason, we wanted to see which crops could generate the most dollars with the least amount of labor.  We recorded the time it took us to harvest each crop in minutes/ yield in pounds.  Although the upright habit of Flamingo spinach is easier for us to harvest in the field, its long stems proved to slow us down while harvesting the trials.  The Tyee spinach had a 15% higher yield per time as compared to the Flamingo spinach.  Our asian braising mix harvested at a yield 155% greater than the Flamingo spinach.  Again, the Salanova lettuce crop had the greatest yield, over 1,200% better than the Flamingo spinach.  The data from these numbers was rather eye opening, and we have since instituted new harvest techniques to improve the speed of our spinach harvests.  During the trial, spinach was harvested by the individual leaf to maximize the crop’s total yields.  We are now harvesting spinach by the clump and have reduced our harvest time for spinach crops by 60%.  We will have to increase the number of bed feet we dedicate to spinach to account for the recovery time of the crop using this harvest technique, but believe that our new harvest techniques will generate significantly higher profit for our spinach crops.

We plan to continue experimenting with techniques for using the poly-film covered non-permanent low tunnels in the coming seasons.  If we can create a system  to withstand wind and rain loads on our farm, we believe that we can greatly increase our production capacity during the winter months.

• High Tunnel, Harvesting
• High Tunnel, 2 Sowing Dates
• 2014 Ivy Creek Season Extension Chart
• Low Tunnels Covered
• Low Tunnels Uncovered

Collaborators: