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

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

Summary

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

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

Initially the study was begun in 2012 but not completed at Fox Hollow Farm (Huntington, NY), where I worked as a Farmer/CSA Manager. Due to a change in employment, I was unable to complete the study at that location. I was granted an extension on the initial grant and was able to fully execute it in 2014 at Makijanian’s Poultry Farm, also 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.

Objectives/Performance Targets

I had planned 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.

There were two treatments and a control, with four replications that were randomly assigned. A total of four, 120 linear foot rows were planted. The rows were 12 inch 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 feat of each treatment.

A soil sample was taken from the growing area before the growing season, between the two crops and again after the growing season for each of the treatment and control plots to determine if there were any changes in pH, micro and macro nutrients. An analysis of the changes, if any, will be included in my final report.

Accomplishments/Milestones

The study was conducted at Makinajian’s Poultry Farm in Huntington.   I was assisted 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, helped me in re-assessing aspects of my grant after some changes were thought of to improve the study’s design.

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 had good to excellent storage. A total of 960 plants of each variety was planted, with a total of 1,920.

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 to applied manually several weeks after time planting. The control group had no mulch whatsoever. For purposes of statistical analysis, the plots were assigned randomly.

Each treatment area was divided in half. One half (20’) was weeded and the other half (20’) was not. The delineation of these two halves was clearly made with tall field stakes. Weeds were hand pulled when they reached at least 6” in height to enable easier hand weeding, and to minimize disturbance of the mulch. Weeding was done three times during the season. The first weeding session was done after the plants were in, but before the mulch was laid, but as these were not part of the suppression aspect of the study, they were not weighed. 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. Note: the weed pressure at this particular growing site was intense. Two other weeding sessions took place; one in the middle of the season and again at harvest.  

It is hoped that the total weight of the weeds will 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 unweeded portions of the treatment beds were weeded and weights were taken at the time of final harvest.

Planting:

The spacing for my 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 my planting area was 1,200 sq. ft.

Using an Excel Spreadsheet, I calculated that I would need to plant 1,920 onion plants to fill the planting area.

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. Despite my affirmation to find a better system for planting, I used the same system I had two years ago, which was laying lines at the row distance needed and ran a tape to measure in-row spacing and used a long tool handle to dibble the holes for the plants. It took me a total of 5.25 hours to plant the entire area, but I also had help from a friend.

Mulching:

The total area mulched with the spent grain equaled about 160 sq. ft. This allowed me to mulch at a 1 inch depth.

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

Some observations: Wet brewer’s grain is wet (and stinky…especially as it ages) and more difficult to apply than Straw. Since I had first-hand experience of using the grain two years ago in my first attempt at this study, I knew that the Spent Grain would more difficult to apply with a 6” spacing without the grain touching the base of the plants, so I abandoned that goal, knowing I had already seen that it would not be problematic in my working with it as a mulch in non-study situations since 2012.

Application of the Spent Brewers Grain mulch for this project was manual and took me 2 hours for the total area of 160 sq. ft. I suspect an inventive farmer with mechanical skills could find a way to apply it with a tractor, but hand mulching was my method for consistent application.

The plants seemed very happy after about two weeks and seemed to be holding their own 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.

Weeding:

I began weeding the plots on June 24 + 25, and again on July 28 and did a final weeding 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 I had to cut them back earlier in the season to prevent shading out the rows next to them. (I kept weights of the toppings and added them to the final weed weights). My final report will contain all of the weights and times for this process.

Harvesting:

Figures of the effects of the mulch on production and the significance, if any, of the type of mulch will be presented in my final report. As I harvested, it became pretty clear that someone had harvested quite a few of the onions in treatment plot number 4, as the impression of what appeared to be fairly sizeable bulbs was evident.

As noted above 960 plants of two storage onions were studied, 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.

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, 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 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 lbs, 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. 

I was able to complete all of the phases of planting, harvesting, and recording for this study, but have yet to compile the statistical analysis of the production of the onions and broccoli, and of the effectiveness of the weed suppression. I will share these results in my final report.

Because mid-study I thought it would be more effective to sample the soil at three points, instead of two, an additional $300 will be needed for the third sampling of the soil from the different treatments and their replications. The statistical analysis, as well as soil sample results for this study will be included in the final report.

Weather was certainly a factor in the production of the Broccoli. While November started with above average temperatures, mid month, the lows reached into the 20s for several consecutive days.

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.

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