Sweetgrass Farm in Hardwick received a 2005 SARE Farmer-Grower grant to assess the viability of direct-seeding mustard greens for seed crop production. For arugula (Eruca sativa), which is much less sensitive to day-length than some other mustard varieties, we believed it might be possible to direct-seed the plants and still get a high-quality seed crop. We thus proposed to compare and contrast three different possible methods of direct-seeding: 1) broadcast seeding, 2) drilled seeding, and 3) drilled seeding of partially heat-killed seed (to reduce seeding rate). The three direct-seeded methods were compared to the control of standard transplanted seedlings. The results showed that the transplanted control did produce a greater yield of seed than any of the experimental methods, but not by a highly significant amount. When evaluated relative to costs of production, we saw that the production cost per pound of seed was lowest for the drilled seed method, leading to the greatest potential return per acre. The broadcast treatment was planted quite thickly to afford good weed control, but this thick planting led to overcrowding of plants, nutrient stress, and the onset of white mold due to lack of airflow. The conclusion is that drilled rows work well and shows the most potential, but with more investigation the broadcast seeding may also prove viable and possibly even more cost-effective, as it allows the earliest planting and affords the greatest weed suppression.
MUSTARD-GREEN SEED CROP PRODUCTION
Jodi and Michael Lew-Smith
1315 Hopkins Hill Rd.
Hardwick, VT 05843
1. To assess the viability of direct-seeding mustard greens for seed crop production
2. To compare and contrast three different possible methods of direct-seeding: 1) broadcast seeding, 2) drilled seeding, and 3) drilled seeding of partially heat-killed seed (to reduce seeding rate)
3. To analyze labor and expenses associated with each method to determine which is most economically sound while simultaneously producing high-quality seed
2. FARM PROFILE
We have farmed our 43-acre farm on Hopkins Hill in Hardwick since the year 2000.
In addition to certified organic seed production on two acres, we also have a two-acre organic apple orchard and we raise grassfed beef cows under intensive grazing management. On the side we raise strawberries, raspberries, small grains, eggs, broilers, and many vegetables for our own family, donating the surplus as we can. Apples, seeds, and beef are the foundation for our farm plan in that the three separate commercial ventures complement one another and spread out labor throughout the season: apples in early spring and late fall, seeds throughout the summer, and cows evenly throughout the year. The cows eat all the diseased apples and their winter manure fertilizes the orchard and seed fields. We wish to keep the apple and beef ventures small so as to maximize our ability for direct sales to our local community. Organic apples and beef are both extremely easy products to sell, such that the time spent in marketing and sales is quite manageable. The seed crops are produced for wholesale sale under contract to a retail seed company.
Vern Grubinger is our technical advisor and he made several important suggestions during the design of the experiment. We have not contacted him for advice throughout the implementation of the project because the work was relatively straightforward.
Our cooperator is Tom Stearns of High Mowing Seeds, Inc. Tom visited the research field during the growing season and made some interesting observations. High Mowing cleaned the seed prior to final weighings and also conducted germination tests on the cleaned seed.
4. PROJECT ACTIVITIES
a. Grain Drill Calibration
We spent 18.5 hours in March of 2005 refitting and calibrating our grain drill to be able to plant seed as small as arugula. This was done using the grass and clover seed box. The initial procedure involved blocking some of the concaves in the seeding spindle to allow less seed to be delivered to the soil. This method proved difficult and ineffective. The final procedure involved adjusting the drill so that very little of the spindle was exposed to the seed. By jacking up the drill and turning the drive wheel, the amount of seed delivered per foot for each row can be determined. The drill was adjusted to deliver the smallest amount of seed possible (the tendency for most clover boxes is overseeding). An average of 6 seeds per foot was the seeding rate used. Telescoping tubes were taken off of the grain box and fitted to the clover box to deliver the seed to the furrow.
b. Planting of Transplant Control
On 4/18/05 we planted in the greenhouse the arugula seedlings to provide the transplant control against which to compare the experimental treatments. 6596 seeds were planted in (70) 50-cell flats and (43) 72-cell flats, which represents 10% over the required number of 6000 plants for a ¼ acre. Seedlings were fertilized with 2 pints of fish emulsion on 5/10/05.
c. Preparation for Experimental Treatments
On 4/26/05 we cultivated and finger-weeded the field to prepare for direct seeding, and we heat-killed seed for one treatment by baking ½ lb. of arugula seed for 15 min. at 400º [Note: this was much too hot as the seed began to burn; the seed should have been baked at 180-200º] The heat-killed seed was mixed in with unbaked seed at a ratio of 3 unbaked :1 baked. [Note: after seeing how germination proceeded, this ratio proved too high in that seedlings were overly thin; the better ratio would be 2:1 or 1:1] This treatment will hereafter be referred to as the “baked” treatment.
d. Planting of Experimental Treatments
Both the broadcast treatment and two drilled treatments were planted on 4/27/05. This proved a lucky window in which to plant, as conditions became cooler and wetter soon thereafter and would have delayed planting for at least another week. Seed was broadcast using an Earthway spinner. Drilled seed was planted in 20” rows using a specially-calibrated Massey-Harris grain drill. The following seeding rates were used:
Broadcast seeding: 3 lbs per ¼ acre
Drilled seeding: ½ lb per ¼ acre
Drilled/Baked seeding: ½ lb total seed (= ~2 oz viable seed)
e. Transplant Control
5-week-old seedlings were transplanted out to the field on 5/27/05. Germination and growth in the greenhouse had unfortunately been somewhat uneven, possibly due to differences in potting soil and/or overly cool temperatures, such that we didn’t have quite enough plants to complete the last two rows of the ¼ acre.
The direct seededarugula began to germinate on 5/6/05, but growth was quite slow due to continued cool and wet conditions. The two drilled treatments were not large enough to cultivate until 5/31/05. The drilled/baked treatment proved to be especially thin in certain areas, such that weeds began to flourish within the rows and required hand weeding. Hand weeding was conducted between June 1-7 with the assistance of hired labor. The full field (excepting the broadcast section) was cultivated again on June 9 and June 13.. We were able to cultivate the spaces in between treatments on 7/5/05.
g. Disease Observations
Sclerotinia sclerotiorum (white mold) was noted in the broadcast section only on 7/7/05. This appeared to be due to the fact that the broadcast section was planted extremely thick, resulting in a lack of airflow around plants. A small amount of Alternaria alternata was observed on plants close to harvest time, but not enough to warrant treatment. The dry conditions throughout the season kept fungal diseases in check.
The broadcast treatment matured earliest, probably due to the stress of overcrowded conditions, and was combined and rough-cleaned on 8/16/05. The drilled section was combined and rough-cleaned on 8/17/05, the control section combined and rough-cleaned on 8/19/05, and the drilled/baked section was combined and rough-cleaned on 8/22/05. We were not able to fully harvest the control section because of mechanical problems with the combine, so we harvested one-third of the treatment and extrapolated the final yield by multiplication.
After harvesting from the field, seed was separated from chaff using a hand-operated fanning mill. Seed was then laid out on canvas tarps to dry under moving air in the greenhouse for ~two weeks, and then cleaned once more in front of a fan before packing into airtight containers and storing in a cool space.
i. Final Cleaning
Seed was repacked into grain bags and brought to High Mowing Seeds in October for final cleaning and germination testing, which was completed on 12/7/05.
Seed Yields By Treatment
Treatment Lot# Rough Weight (lbs) Clean Weight† (lbs) %Germ
a. Broadcast SGF11-B 71 57 88
b. Drilled SGF11-D 160 126 89
c. Drilled/Baked SGF11-BD 138 108 85
d. Control SGF11-C 180* 153* 86
*Indicates that this number is actually an extrapolation from harvest of one-third of the quarter-acre plot, see below for discussion
† Weight is for yield of one-quarter-acre plot
Labor and Expenses Associated with Each Method
Treatment Labor hours Cost Expenses Total Cost Cost/pound
a. Broadcast 7.75 $155 $29.70 $184.70 $3.24
b. Drilled 13.75 $275* $4.95* $279.95 $2.22
c. Drilled/Baked 45.25 $813** $4.95 $817.95 $7.57
d. Control 54.75 $1095 $74.75 $1169.75 $7.65
*does not include time or expense of modifying grain drill to plant Brassica seed
** labor costs higher than planned due to weed issues, caused in part by overly-thin sowing
The 2005 growing season was a good season in most respects. We had unseasonably warm conditions in April that allowed the fields to dry out just long enough for planting by the last week of the month. May followed with a steady period of cool, wet conditions, during which seeds germinated but did not grow very rapidly. Conditions became dry and warm again in June, but arugula, being quite drought tolerant, showed no adverse response to the heat and began to grow steadily. Rainfall throughout the remainder of the season was steady but not overly high, resulting in a low incidence of fungal disease.
These conditions affected our results in that the long period of cool and wet conditions in May made everything grow more slowly. The rest of the season, though, was an unusually good one such that we did not get to measure the various methods against one another under late-season stress conditions.
Our findings showed clearly that even though yields per acre were highest with the standard transplant method, the sharp drop in production costs for the direct-seeded methods will result in a higher return per acre. For example, given an average wholesale arugula seed price of $15 per pound (for organic seed), the return per acre for the transplant method in this growing season would have been $4498.20 ($7.35/lb profit X 612 lbs per acre), whereas the return per acre for the drilled treatment would have been $6441.12 ($12.78/lb profit X 504 lbs per acre). This represents a 30% increased profit margin.
The one economic factor that we didn’t include in any of the equations was the time and money we spent in modifying a grain drill to be able to plant small Brassica seed at an acceptably low rate. After considerable time we were able to have our grain drill plant at approximately one seed every two inches, which is still more dense than optimal. Some of this time, however, involved experimenting with different methods of adapting the drill. Further modifications would be needed for optimal seeding, if indeed it could be achieved. We did not include these expenses in any of the profit calculations as we considered this time to be a matter of capital investment. A grower who wished to direct-seed Brassicas over a significant acreage might find it worthwhile to invest in a precision seeder.
Our results indicate that all three of the methods we evaluated led to production of equivalently high-quality seed, but that one of the methods, drilling, was clearly more cost-effective than the others under the parameters and conditions of this particular experiment. The baking/drilling method was the least cost-effective and we did not feel that it showed enough promise to warrant further investigation. In contrast, the broadcast method showed considerable promise, despite the less-than-exceptional yield data we collected in this given year.
The next step, in our view, would be to more closely evaluate the parameters required to optimize the broadcast seeding method. The greatest advantage of this method is that it allows seeding without heavy equipment, and can thus be more reliably performed in the last week of April. Trials done this summer at High Mowing Seeds showed that planting these crops even a week later than we did can severely affect yields. Thus we believe it is critical to get seed in the ground no later than the 1st of May. Also, the broadcast method allows for maximal weed suppression by the crop plants, potentially eliminating the need for cultivation and hand-weeding.
As we were attempting broadcast seeding for the first time during this project, and only had one treatment plot to work with, we erred on the side of caution by seeding it quite heavily. We were concerned that if we seeded it too lightly and germination wasn’t particularly good, the whole plot would overgrow with weeds and would have to be tilled under. In fact what happened was that the arugula came up in a lush lawn, easily smothering weeds in the early season, but then overcrowding each individual plant such that none of them set much seed and there was so little airflow that white mold became a problem. We would like to better assess the method by seeding at several lower rates to see which might strike a balance between weed suppression and overcrowding. If this seeding rate can be optimized, the greater flexibility in planting time and possibility for reduced weed pressure might make broadcast seeding the method of choice.
If conditions prove favorable for allowing heavy equipment on the fields before May 1st again this year, we plan to compare drilling seed to broadcast seeding at two different rates. The broadcast seeding was not successful enough in this initial study to warrant complete reliance on that method, but it showed enough promise to warrant further investigation. The drilling method proved reasonably reliable, but still requires a certain amount of hand-weeding, a factor we would greatly like to minimize. Broadcasting any thinner will require all hand weeding, as no mechanical cultivation will be possible.
A. Outreach article submitted to “NOFA-Notes” in January of 2006 (see enclosed)
B. Outreach article submitted to Vern Grubinger for use in “Agriview” (see enclosed)
C. Outreach article and final report submitted to Richard Wiswall for use by the NOFA-Vermont Organic Seed Production Technical Assistance Program.
D. Results discussed with Tom Stearns of High Mowing Seeds for dissemination during
workshops and other programs for seed growers.
E. NOFA-VT workshop held during course of project entitled “How to Design Your Own
On-Farm Trial.” This workshop was not about the SARE-funded project itself,
but rather used the project as an example of on-farm research, and thus allowed other growers to see the project in progress. Attendance was low due to heavy rain that day, but the workshop helped spread word of the project.
Jodi and Michael Lew-Smith
January 24, 2006