Effectiveness of wet spent brewer's grains as mulch in mixed vegetable production

Final Report for FNE12-743

Project Type: Farmer
Funds awarded in 2012: $6,989.00
Projected End Date: 12/31/2015
Region: Northeast
State: New York
Project Leader:
Regina Dlugokencky
Seedsower Farm
Expand All

Project Information

Summary:

The purpose of this study was to investigate the effectiveness of Spent Brewer’s Grain, a by-product of Beer Breweries, as a low-cost option for suppressing weeds in organic onion and broccoli production. This study compared three treatment types: Straw, Spent Brewer’s Grains, and Control Plots (no mulch whatsoever) for weed suppression, evaluated the quality and weight of the two crops, and finally, analyzed results of micro and macronutrients of the three plots. There were four replications of the three treatment types.

A significant difference in time spent weeding and weight of weeds was found between the weeded Straw plot and the un-weeded Control plot.  There was also a significant difference in time spent weeding and weight of weeds between the weeded Spent Brewer’s Grain plot and the un-weeded control plot, and the least amount of time was spent weeding the straw-mulched plots during the growing season. Quality was not affected by any treatment, and was high for both crops. 

The results suggest that control of weeds can be best achieved by mulching, regardless of type of mulch, and weeding combined.

  • No significant difference was found in time spent weeding and weight of weeds between the Straw Plots (weeded or un-weeded) and SBG Plots (weeded or un-weeded) and the un-weeded control plot.

This data suggests that SBG is as effective as Straw as mulch for weed suppression.

In terms of effects of type of mulch on yield, a significant difference in weight was found only between the onions mulched with straw (whether weeded or un-weeded) and those grown in the un-weeded Control Plot.  No statistical significance was found in the yield of Broccoli following the onions between the three treatment plots.

Macro and Micro Nutrient analysis revealed a drop in Potassium and Sulfur levels as compared to soil samples at pre-plant, and an increase in Sodium, Calcium, Magnesium, Manganese, and Zinc. Calcium and Magnesium were higher in the Straw and Control plots than in Spent Brewer’s Grain plots, when compared to pre-plant samples, even though these two nutrients are associated with Spent Brewer’s Grains.

The land where I conducted this study on had very, very high weed pressure and so results may have been diminished.  This scope of this particular study doesn’t go beyond one growing season to evaluate how Spent Brewers Grain affects soil quality. I would hypothesize that the value of SBG is underestimated but would be interested to see if the benefits are longer lived and how they would change over time.  I posit that even more benefits of this product are yet to be explored, including investigating the effect of SBG on soil organisms. Anecdotally, I have observed a higher population of earthworms in soil that has been mulched with SBG than soil that has not.

Introduction:

Organic vegetable production prohibits using many forms of weed control afforded to the conventional grower. Organic growers are limited to hand weeding, cultivation, and mulching to keep weed pressure to a minimum. Hand weeding is time consuming and thus labor costs are high. Cultivation is limited in long-term effectiveness. Mulching material for Long Island (NY) farmers is an expensive option since large-scale cereal farming is not done on Long Island.

With the establishment of over 20 new Microbreweries on Long Island and more in the planning stages, Spent Brewer’s Grains (SBG), a byproduct in the brewing process, are becoming more abundantly available. A Microbrewer brewing a single seven barrel batch (217 gallons) of beer, will consistently produce a large amount (~220 pounds per brewing day) of this material, leaving brewers with the problem of quick disposal. Most Microbrewers consistently brew more than two batches of beer each week.

Spent Brewer’s Grain offers many benefits to growers. According to the Cooperative Extension Service of Alaska of every 100 pounds of SBG, 28 pounds are nutrient based. Nutrients from SBG are composed of Nitrogen (1 pound per 100 pound of SBG), Phosphorus, Potassium, Calcium and Magnesium, though the nutrients other than Nitrogen are at trace levels.

SBG has a Nitrogen content of ranging from 1-4 pounds of nitrogen per 100 pounds of SBG, or 1 – 4% which is comparable to Cow Manure at the low end (1.7%) or Sheep Manure at the high end (3.75%), and a C:N ratio ranging from 12:1 to 15:1. Often given to livestock producers or used as compost feedstock, this nutrient-rich material is an ideal, low cost option for more immediate needs.

My proposal is to study if wet Spent Brewers Grains can be effectively used as an inexpensive mulching material.   In addition to assessing weed control, effect of Spent Brewer’s Grains on quality and yield of two crops, as well as changes to pH, micro and macronutrients were also measured.

According to the Organic Farming Research Foundation, the number of organic farms has increased 20% each year since 1997. SBG could be an effective and inexpensive tool to assist new and financially stretched organic farmers suppress weeds.

Outreach will be through local and regional Agricultural conferences, Seedsower Farm’s website, my blog, agricultural based listservs, in discussions with other farmers, and possibly publication.

In January 2012, I was awarded a Sustainable Agriculture Research & Education (SARE) Farmer’s Grant to study the effectiveness of spent brewer’s grains as a direct-applied mulch in organic vegetable production. I was granted an extension on the initial grant and was able to fully execute it in 2014 at a certified organic farm in Huntington, NY. In this second iteration of the grant, I chose to use storage onions for the first crop and broccoli for the second. Soil testing was expanded to include soil sampling between the two crops, in addition to the initial testing and testing at the end of the growing season.

In order to execute the study outlined above, I chose to study two consecutive crops that span the entire growing season on Long Island (March – November).

Storage onions were chosen because they are notoriously intolerant of weeds and have little or no canopy with which to shade weed seeds, and as a storage variety, the onions could be sold at a Winter Farmer’s Market. Broccoli was studied, because of the ease of transplanting into an already mulched area and because it could be grown following onions and would complete the season to study the effectiveness of weed suppression for the spent grain vs. straw. Broccoli is also a valuable crop for fall markets on Long Island, and the timing of the harvest was close to the Thanksgiving Holiday where sales would be brisk.

 

Project Objectives:

The study was conducted in 2014, with assistance in the design and of the project by Dr. Margaret Tuttle-McGrath, Plant Pathologist, from Cornell University Long Island Horticultural Research and Extension Center. Dr. Tuttle-McGrath has also helped me with questions during the season and will help with the statistical analysis and interpretation. My Farmer Grant Specialist, Carole Delaney, assisted in re-assessing aspects of my grant after some changes were thought of to improve the study’s design.

Planting:

Two varieties of onions transplants were purchased from Johnny’s Select Seeds: Patterson & Red Zeppelin. Both onions were of similar size and maturation date, and was reported to have good to excellent storage. A total of 960 plants of each variety was planted, for a total of 1,920.

The spacing for the onions on 12 inch beds was 6 inches a part in-row, with the two varieties spaced approximately 6 inches apart on a diagonal line. The total measurement for the planting area was 1,200 sq. ft. Treatment plots were randomly assigned.

On April 3, I began to prep the fields and lay out the rows, and planted Row 1. Rows 2 through 4 were planted on April 5. The plant spacing was accomplished by laying lines at the row distance needed with a measuring tape run to measure in-row spacing and used a long tool handle to dibble the holes for the plants. A total of 5.25 hours was required to plant the entire area.

A trench was made between the two rows of onions in each plot and Cheep Cheep Organic Fertilizer (4-3-3) was laid down between them. Approximately two pounds per 120 linear feet was applied.

The project called for the first treatment to include straw mulch at one inch in depth; the second treatment would use wet SBG as mulch also at a depth of one inch. Both mulches were applied manually several weeks after planting time. The control group had no mulch whatsoever. For purposes of statistical analysis, the plots were assigned randomly.

Mulching:

The total area mulched with the spent grain equaled about 160 sq. ft. and was mulched at a 1 inch depth.

SBG mulch was laid down on May 14 (Rows 1 + 4) and again on May 20 (Rows 2 + 3) and required approximately 754 pounds of material. All of the Grain from this year’s study was provided by Blind Bat Brewery in Centerport, New York.

Application of the Spent Brewers Grain mulch for this project was manual and took two hours for the total area of 160 sq. ft Wet brewer’s grain is wet (and stinky…especially as it ages) and a bit more difficult to apply than Straw. First-hand experience of using the grain in a previous study provided insight on the difficulty of applying it with a 6” spacing without the grain touching the base of the plants. Since I previously found no negative effects of the SBG being placed right up to the side of plants in non-study situations, I applied the grain without concern about it touching the plants. As a result, it was easier (and faster) to apply than the straw. The plants were growing well after about two weeks and seemed to be thriving in the wet mulch.

Straw mulch was also laid down on May 14 and took approximately 3 hours for the total area of 160 sq. ft. Three bales covered the four treatment areas at the depth of 1 inch.

Weeding:

Weeding was done June 24 + 25, and again on July 28 + 29, with a final weeding done while harvesting onions in August. Weeding and weighing was quite time consuming, since the weed pressure at this site was very high. The weeds in the un-weeded sections were so tall that they had to be cut back earlier in the season to prevent shading out the rows next to them. (Weights of the toppings were added to the final weed weights.)

Harvesting:

As noted above 960 plants of two storage onions were planted (Patterson and Red Zeppelin). All together, I harvested 758 Patterson (yellow) Onions weighing a total of 182.58 lbs and 606, and Red Zeppelin (red) Onions weighing 147.28 lbs. These total included any greens left on the plant, though most of the foliage had dried back to the bulbs.

As I harvested, it became pretty obvious that someone had harvested (aka poached) quite a few of the Red Zeppelin onions in replication row number four, as the impression of what appeared to be fairly sizeable bulbs was still evident.

Broccoli Planting and Harvesting:

Broccoli starts were begun on July 4 and planted on August 20. A single row of broccoli was planted in each of the study plots and was spaced at 18 inches apart (80 plants per 120 row feet), for a total of 320 plants. The variety, ‘Marathon’ was chosen for its cold hardiness and anticipated production of side shoots, but a cold snap in mid-November where temperatures dropped into the twenties at night, seriously diminished the potential for some of the plants to ever reach full maturity and for mature plants to continue with side shoot production. Of the 320 Broccoli Plants, I was able to harvest 299 main heads weighing 128.2 lbs. Side shoot production weighed in at a mere 6.2 pounds, but I do not include these in my calculations. Harvesting began on November 4 and was completed on November 30.

Soil Testing:

Soil samples were taken at three points: pre-plant, between onions and broccoli crops and at the end of season. 

Because mid-study I thought it would be more effective to sample the soil at three points, instead of two, additional funds were requested for the third sampling of the soil from the different treatments and their replications. As it turned out, the samples that I took both in August (between the onion harvest and broccoli planting) as well as the end of season soil samples were insufficient in quantity. To address this I chose to combine samples for all four replications of each of the treatments. This resulted in a total of 7 soil samples: One for pre-plant baseline measurement, three for Straw, SBG and Control treatments on 8/19 and three for the same treatments taken on 12/15.

 

Cooperators

Click linked name(s) to expand
  • Dr. Margaret Tuttle-McGrath

Research

Materials and methods:

There were two treatments and a control, with four replications that were randomly assigned. A total of four, 120 linear foot rows were planted. Rows were 12 inches wide with paths between each row at 24 inches wide. Each row included treatment plots with SBG, Straw, and a control plot with no mulch. Each treatment plot consisted of 40 linear feet of row space, for a total of 160 linear feet of each treatment.

A total of three soil samples were taken from the growing area: before the growing season (pre-plant on 4/13), between the two crops (8/19) and again after the growing season (12/15) for each of the treatment and control plots to determine if there were any changes in pH, micro and macro nutrients.

Each treatment area was divided in half. One half (20 feet) was weeded throughout the season as needed and the other half (20 feet) was weeded after the onion harvest. The delineation of these two halves was clearly made with tall field stakes. Weeds were to be hand pulled when they reached at least 6 inches in height to enable easier hand weeding, and to minimize disturbance of the mulch. (Note: the weeds grew so vigorously that they were pulled at a larger stage of growth than planned, and the mulch was ultimately disturbed.)

Weeding was done three times during the season. The first weeding session was done on all treatment plots after the plants were in, but before the mulch was laid. Since these weeds were not part of the suppression aspect of the study, they were not weighed, nor was the time used to weed counted.

After the mulch was laid, the weeds that were pulled from the weeded half were weighed, with care taken to remove as much soil as possible from the root system. Two other weeding sessions took place; one in the middle of the season and again before final harvest.  It was hoped that the total weight of the weeds would provide quantitative measures of the weed control for the two treatment areas with mulch and will allow comparison of the effectiveness of the SBG as a weed suppressant.         

The control plots without mulch were also split in half, delineated by field stakes and were weeded and weighed to determine the quantity of weeds that would normally grow without a mulch barrier. The un-weeded portions of the treatment beds were weeded and weights were taken at the time of final harvest.

Treatment Schematic

   

SBG-W

SBG-W

SBG-NW

Control-W

SBG-NW

SBG-NW

SBG-W

Control-NW

Straw-W

Control-W

Straw-W

SBG-NW

Straw-NW

Control-NW

Straw-NW

SBG-W

Control-NW

Straw-NW

Control-NW

Straw-W

Control-W

Straw-W

Control-W

Straw-NW

Row 1

Row 2

Row 3

Row 4

Key:    SBG=Spent Brewer’s Grains            
           W=Weeded: Weeded throughout the season
           NW=Unweeded: Weeded at end of season

Research results and discussion:

All of the phases of planting, harvesting, and recording for this study are complete, following are the statistical results and total weights recorded for each treatment and replication. Statistical analysis of the production of the onions and broccoli, and of the effectiveness of the weed suppression was done using JMP Statistical Analysis Software and was conducted by Karen LeMarsh, Research Support Specialist and assistant to Dr. Margaret Tuttle-McGrath, Long Island Horticultural Research and Extension Center.

Weed Suppression – Statistical Results (Actual Weed weights can be found in the Accomplishments section of this report)

   

Weeding Averages

 

Trt

Treatment

Weight (Pounds)

Time Spent (Minutes)

 

1

Control (not weeded)

117.7

a

73.8

a

 

2

Control (weeded)

71.5

abc

63.3

abc

 

3

SBG (not weeded)

115.1

abc

65.0

abc

 

4

SBG (weeded)

61.0

bc

43.8

bc

 

5

Straw (not weeded)

70.1

abc

56.3

abc

 

6

Straw (weeded)

27.6

c

36.8

c

 

 

P-value (treatment)

0.0007

0.0053

 

 

Numbers in each column followed by the same letter or no letter are not significantly different from each other (Tukey’s HSD, P=0.05).

 

               

  • A significant difference in time spent weeding and weight of weeds was found between the weeded Straw plot and the Un-weeded Control plot.
  • There was also a significant difference in time spent weeding and weight of weeds between the weeded Spent Brewer’s Grain (SBG) plot and the un-weeded control plot.

The least amount of time was spent weeding the straw-mulched plots during the growing season and the total weight of the weeds was less than for the control plot that was weeded once at the end of the experiment. The plots mulched with SBG also took less time and resulted in lower total weight of weeds as compared to the control plots that were weeded only once.

The results suggest that control of weeds can be best achieved by mulching, regardless of type of mulch, and weeding combined.

  • No significant difference was found in time spent weeding and weight of weeds between the Straw Plots (weeded or un-weeded) and SBG Plots (weeded or un-weeded) and the un-weeded control plot.

This data suggests that SBG is as effective as Straw as mulch for weed suppression.


Onion Harvest – Statistical Results

   

Onion Yield-Averages

   

Red Zeppelin

Patterson

Trt

Treatment

Number

Weight (Pounds)

Number

Weight (Pounds)

1

Control (not weeded)

23.5

4.0

29.5

3.2

b

2

Control (weeded)

25.8

5.7

33.5

8.0

ab

3

SBG (not weeded)

24.0

5.0

29.0

6.1

ab

4

SBG (weeded)

23.3

6.7

27.0

6.6

ab

5

Straw (not weeded)

26.8

7.8

37.5

10.2

a

6

Straw (weeded)

28.3

7.6

33.0

11.6

a

 

P-value (treatment)

0.8804

0.4069

0.1206

0.0062

             
 

Numbers in each column followed by the same letter or no letter are not significantly different from each other (Tukey’s HSD, P=0.05).

As a group (not separated by variety) a significant difference in weight was found only between the onions mulched with straw (whether weeded or un-weeded) and those grown in the un-weeded Control Plot.

Below are the actual total weights by variety and treatment of the onions. The statistical analysis done did not distinguish between the two varieties, so it was done on the total number onions in each treatment.

Although statistical significance for weight differences could not be found, it does appear that the yields were greatest from onions grown in the straw treatment.

 

 

 

 

 

 

 

Onions

     

 

Treatment

Patterson

Red Zeppelin*

 

 

 

Number

Pounds

Number

Pounds

 

 

Control-Un-weeded

118

12.8075

94

16.16

 

 

Control-Weeded

134

32.03625

103

22.675

 

 

Control-Total

252

44.84375

197

38.835

 

 

SBG-Un-weeded

116

24.34375

96

19.98125

 

 

SBG-Weeded

108

26.225

93

26.81

 

 

SBG-Total

224

50.56875

189

46.79125

 

 

Straw-Un-weeded

150

40.63125

107

31.12125

 

 

Straw-Weeded

132

33.4275

113

30.53

 

 

Straw-Total

282

74.05875

220

61.65125

 

 

Totals

758.00

169.47

606.00

147.28

 

 

*Onions harvested by poacher!

     

 

 

Total of Each Variety Planted=960

     

 

               

 

The onions from the Straw treatment group were also larger in size, averaging 4.20 oz. (Patterson) 3.96 oz. (Red Zeppelin) compared to 3.61 oz. and 3.96 oz. for those mulched with SBG; and 2.84 oz. (Patterson) and 3.15 oz. (Red Zeppelin) in Control Group.

 

Patterson

Red Zeppelin*

Treatment

Number

Ounces (Average)

Number

Ounces

(Average)

Control-Avg. Unit Weight

252

2.847222222

197

3.15411168

SBG-Avg Unit Weight

224

3.612053571

189

3.96116402

Straw-Avg Unit Weight

282

4.201914894

220

4.48372727

 

Broccoli Harvest – Statistical Analysis

   

Broccoli Yield Averages

Trt

Treatment

Number

Weight (oz)

1

Control

24.8

160.7

2

SBG

27.3

179.2

3

Straw

22.8

173.1

 

P-value (treatment)

0.2939

0.7209

 

There was no statistical significance in the yield of Broccoli following the onions between the three treatment plots. While not statistically significant, the greatest yield was found in the plots where Spent Brewer’s Grains were used as mulch. 

Soil Samples – Results

(Please see Appendix for comparison of 08/19 and 12/15 values to pre-plant)

0413-Pre-plant Sample

0819=Midseason Sample

1215=End of Season Sample

 

Soil Sample Results

 

           

Sample ID

Pre Plant

Straw 1215

SBG    1215

Control 1215

Straw 0819

SBG    0819

Control 0819

Lab Number

64

65

66

67

68

69

70

Sample Depth in inches

6

6

6

6

6

6

6

Total Exchange Capacity (M. E.)

15.81

15.35

15.79

16.63

17.86

16.96

14.62

pH of Soil Sample

6.4

6.9

6.7

7.0

6.6

6.2

6.5

Organic Matter, Percent

10.21

17.73

21.30

16.94

18.34

18.83

14.98

 

SULFUR:                             p.p.m.

20

11

10

11

13

17

16

Mehlich III
Phosphorous:                  
ppm

264

250

313

267

282

359

308

SODIUM:                             ppm

11

21

24

27

15

16

15

 

Calcium (60 to 70%)

64.96

74.43

72.15

75.86

71.31

65.55

65.48

Magnesium (10 to 20%)

14.97

17.67

16.84

18.04

16.43

15.95

20.47

Potassium (2 to 5%)

5.76

1.32

1.17

0.98

1.1

0.88

1.21

Sodium (.5 to 3%)

0.3

0.6

0.65

0.72

0.37

0.41

0.45

Other Bases (Variable)

5

4.5

4.7

4.4

4.8

5.2

4.9

Exchangable Hydrogen (10 to 15%)

9

1.5

4.5

0

6

12

7.5

 

Boron (p.p.m.)

0.72

0.9

0.84

1.02

0.9

0.9

0.67

Iron (p.p.m.)

304

225

234

216

246

249

243

Manganese (p.p.m.)

17

26

26

25

29

27

27

Copper (p.p.m.)

1.82

1.7

1.78

1.71

1.58

1.69

1.77

Zinc (p.p.m.)

9.17

19.01

19.95

20.99

20.31

20.45

22.89

Aluminum (p.p.m.)

618

175

169

176

218

240

212

Soil samples were taken three times during the growing season. A pre-plant sample was taken on April 13, a midseason sample was taken on August 19 after the onions were pulled and prior to Broccoli being planted. The final sample was taken on December 15 after the Broccoli was harvested. The soil tests were sent to Logan Labs for analysis in February, 2015.

The results from the soil samples were not as straightforward as I would have anticipated. Not being a soil scientist, some of the results were a bit confusing. After doing a little bit of research, I found data that helped illuminate the results a bit.

Onion growth requires three main nutrients for growth: Nitrogen (N) and Potassium (K) and also Sulfur. Of the micronutrients needed for onion growth, Boron and Iron the most important.

As the soil sample above indicates, the Potassium and Sulfur levels found in the soil at pre-plant on April 13 was higher than at any other sampling point. Perhaps this can be attributed to the uptake by the onions for growth. Although Boron and Iron are both needed in small amounts for vigorous growth, it appears that only Iron was lower than at pre-plant.
           
Nutrient needs for Broccoli include an abundance of Nitrogen and sufficient Boron.

Without statistical analysis behind these figures, I can only make a judgment on them at face value: pH levels were unstable, with values at 6.4 at pre-plant, dropping to 6.2 at the first testing point for the SBG Plots, and rising to a pH level of 7.0 in the Control Plot for the samples take on 12/15.

Organic matter measured at 10.21% at pre-plant, and as one would expected increased in the Straw and SBG plots, with the highest values in the latter. It is unclear to me why organic matter would have also risen in the Control Plots.

In regard to other nutrients that were higher later in the season than at pre-plant, there was also an increase in Sodium, Calcium, Magnesium, Manganese and Zinc. The 12/15 soil sample results showed Calcium and Magnesium (two micronutrients that are associated with SBG) were higher in the Straw and Control plots in comparison to pre-plant, so no solid correlation could be made with the SBG.

The main purpose of this study was to determine if Spent Brewer’s Grains would be an effective and inexpensive alternative to using straw as mulch in organic onion production.   A plus side to mulching with organic materials is the benefits of increased water retention and possible increase in organic matter and nutrients. These benefits are not only important to crops that are currently being grown but also to crops that follow. I will discuss the implications of using straw versus SBG as mulch below.

Weed Suppression

This study has illuminated the cost of labor that is required to successfully grow onions using organic methods. Below is a table of the actual total weight of weeds and time taken to weed by treatment type. Using a scenario where a laborer is paid a wage of $10 an hour, we can clearly see that using hand cultivation alone is the most costly of methods to control weeds.

While the straw was most effective in suppressing weeds, it does cost money if not produced on farm and labor is still needed to apply it. The numbers below were generated from data collected on a 1,200 square foot piece of land, in an effort to more realistically reflect a grower’s labor costs, I have extrapolated my results by multiplying my expenses by 36.378 to estimate costs for a plot the size of one acre. (43650/1200 = 36.378)

The reduction of labor costs by using a combination of hand weeding mulch of some type can be noted in the table below.

Spent Brewer’s Grain, a free product, worked well enough as a weed suppressant to indicate its value as an alternative to straw, at least in parts of the country where the cost is prohibitive.

Treatment

Weed Wt (lbs)

Weed Time (Hours)

Mulching Time (Hours)

Labor Cost @ $10 per hour

Mulch Cost

Total Cost for Weed Management 1,200 sf

Total Cost for Weed Management Per Acre

Total Control Un-Weeded*

470.83

4.92

0.00

$    49.17

0.00

$       49.17

$ 1,784.75

Total Control Weeded**

286

4.22

0.00

$     42.17

0.00

$       42.17

$ 1,530.65

Total SBG Un-Weeded*

460.38

4.33

0.50

$     48.33

0.00

$       48.33

$ 1,754.50

Total SBG Weeded**

244

2.92

0.50

$     34.17

0.00

$       34.17

$ 1,240.25

Total Straw Un-Weeded*

280.34

3.75

0.75

$     45.00

6.00

$       51.00

$ 1,851.30

Total Straw Weeded**

110.5

2.45

0.75

$     32.00

6.00

$       38.00

$ 1,379.40

*Unweeded=treatment plots weeded at end of season only.

**Weeded=Weeded twice during the growing season

As an aside, it is worth noting the difference in weed populations depending on the treatment. Control Plots and Straw tended to have great varieties of weeds as compared to the SBG Plots, but the weeds that did grow in the SBG plots were monstrous in size: Lambsquarters roots from one SBG plot weighed in at 24 lbs. There may be some quality to the SBG that may suppress some weeds, or perhaps these particular weeds gained an head-start advantage and as a result reduced emergence of other varieties.

Also noticed, but impossible to capture with a photo was the deeper color of the weeds that grew in the SBG plots. These were much greener than those in the adjacent straw plots. One possibility is that the Nitrogen level in the SBG was a factor.

Types of Weeds Noted by Treatment Type

Control

Straw

SBG

Galinsoga

Chickweed

Galinsoga

Grasses

Clover

Lambsquarters (5 – 6 Ft)

Lambsquarters

Galinsoga

Pennyslyvania Smart Weed

Pennsylvania Smart Weed

Grasses

Pigweed (1/4 ” diameter Stems!)

Pigweed

Lamium

 

Purslane

Pennsylvania Smart Weed

 

 

Plantain

 

 

Purslane

 

Finally, the weed pressure at the study site was beyond that of any other growing space I’ve experienced, so the effectiveness of the mulch treatments may have been diminished in comparison to a site where weed pressure is less intense. The Farmer who owns the property regularly spreads farm-produced compost. Perhaps the process by which he makes this compost doesn’t fully kill weed seeds. The annual application of compost may also explain the high organic matter.

Produce Quality

The produce quality for both crops was high. The storage onions cured well and continue to be enjoyed by the researcher. (It would be interesting to expand the study to see which onions held the longest depending on treatment type).

The Broccoli was also of high quality, but weather proved to be a factor in its production. While November started with above average temperatures, mid-month, the lows reached into the 20s for several consecutive days. It would have been interesting to see how much side shoot production would have yielded if we had not had the frigid temperatures so early in the growing season.

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary

Education/outreach description:

The results of this study will be shared on two major agricultural related listservs: Comfood (Tufts University) and ANET-MG (SARE), and others as they are identified.

In addition, the results of this survey will be available on my Website (seedsowerfarm.com), my Blog (http://farmersgrant2014.blogspot.com/) and through informal conversations with other organic growers. I have contacted Growing for Market, Small Farms Quarterly, and NOFA’s Natural Farmer Newspaper to submit this study and its results for publication.

Project Outcomes

Assessment of Project Approach and Areas of Further Study:

My recommendations for future research into using Spent Brewer’s Grains would include finding a location that has less intense weed pressure. The land where I conducted this study on had very, very high weed pressure and so results may have been diminished.

Additionally, if doing another study of this sort, and because I definitely had some theft of onions, I would ensure that signage noting that a study is being conducted is visible, so that impromptu, midnight Pick-your-own activities don’t occur.

This scope of this particular study doesn’t go beyond one growing season to evaluate how Spent Brewers Grain affects soil quality. I would hypothesize that the value of SBG is underestimated but would be interested to see if the benefits are longer lived and how they would change over time.

Finally, besides appearing to be suitable mulch for onion production, further studies on other crops may yield even more promising results, as would investigation into the benefits Spent Brewer’s Grain has on improving both soil condition and fertility.

Potential Contributions

The potential of SBG to reduce expenses and labor for organic farmers is evident. Craft breweries are opening at a rapid pace all across the country and brewers are eager to have this byproduct taken off of their hands. Organic growers with limited budgets can reap these “free” rewards if they are willing to work with the brewery to pick up the SBG on a timely basis.

I posit that even more benefits of this product are yet to be explored, including investigating the effect of SBG on soil organisms. Anecdotally, I have observed a higher population of earthworms in soil that has been mulched with SBG than soil that has not.

In addition, I would be curious to see if a difference exists between SBG and Straw in the soil nutrition on fallow growing areas.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.