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

This project is to study the effectiveness of spent brewer’s grains as a direct applied mulch in organic vegetable production
The question is if wet Spent Brewers Grains 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 measurements on the changes to pH, micro and macronutrients.

Objectives/Performance Targets

The two crops chosen were consecutive crops that are grown throughout the growing season. Shallots are notoriously intolerant of weeds and have little or no canopy with which to shade weed seeds, and because they are a desirable and profitable market crop. Broccoli has an ease of transplanting into an already mulched area and because it can be grown following onions and will complete the season for the purpose weed suppression. Broccoli is also a valuable crop for fall markets on Long Island.

The study design was two treatments and a control to be replicated four times on the same parcel, and randomly assigned. This means a total of four, 120 foot rows. The rows are 42 inch wide with paths between each row at 18 inches wide. Each row included treatment plots with SBG, Straw and a control plot with no mulch. Each treatment plot consisted of 40 feet of row space.

A soil test planned included pH and macro and micronutrient analysis was to performed on the field before the growing season and again after the growing season for each of the treatment and control plots to determine if there were any changes in these measurements. An analysis of the changes, if any will be included in my final report.

Accomplishments/Milestones

The study was conducted at Fox Hollow Farm in South Huntington, where I worked as the Farmer/CSA Manager from January – August, 2012. I was assisted in the design of the project and the statistical analysis and interpretation by Dr. Margaret Tuttle-McGrath, Plant Pathologist, from Cornell University Long Island Horticultural Research and Extension Center.

As previously noted, my intention for 2012 was to study the effect of Wet Spent Brewery Grain (SBG) as a direct applied mulch on Shallots and then Broccoli. Unfortunately, due to unexpected changes I was unable to complete the study in 2012, so journal and data entries are only related to the allium portion. In addition, soil samples were taken and are stored in the freezer. I am hopeful that I will have a parcel on which to repeat and conclude the study in 2013.

Two varieties of shallots were started from seed purchased from Johnny’s Select Seeds: Saffron F1 on February 5, and Ambition F1 on February 11. One additional planting of the same two varieties was made on March 3, but these seemed too small to include in the study.

Because I was concerned that I would not have enough plants to utilize the entire area, we decided the plot size would be too small to be manageable and yield enough data for statistical analysis.
To make matters worse, my shallot plants became infested with black aphids and though I successfully eradicated the plants of this pest using an air compressor, they seemed weak compared to onion plants I had purchased from Johnny’s Selected Seeds for the CSA I was running.

My technical advisor and I decided to substitute onions for shallots. Because I wanted to include a specialty onion in my study and wanted onions that would store well, I chose Red Marble Cipollini. This variety of Cipollini onions are full sized at Avg. 1 1/2-1 3/4″ diameter by 3/4-1”. The other variety I chose was Ailsa Craig, a sweet, non-storage onion, which is approximately 4” wide and weighs up to 2 lbs at maturity. The two varieties would also allow me to observe how the mulch affects very small and very large onions.

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 be applied manually at the time of planting and replenished, if needed, through the growing period to keep depth level consistent. The control group is to have 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 30” field flags. Weeds were to be hand pulled when they reached at least 6” in height (or 7-14 days) to enable easier hand weeding, especially of the mulched areas where hoeing would disturb the mulch. The weeds that were pulled from the weeded half were to be weighed and should have also been counted each time it was weeded (7-14 days), with care taken to remove as much soil as possible from the root system.

It was hoped that the total weight and counts 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 split in half, delineated by field flags and weeded, weighed and also counted to determine the quantity of weeds that would normally grow without a mulch barrier.

Planting:

The spacing for my onions on 48 inch beds was 8 inches apart, with the two varieties spaced approximately 12 inches apart. The total measurement for my planting area was 1,920 sq. ft.
I calculated that I would need to plant 2,880 onion plants.

On May 4, I started planting with a jig and a hand dibble, but soon realized this method was too laborious and slow, for the amount of linear footage that needed planting. Instead, resorted to 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. I completed planting on May 5. It took me a total of 12 hours to plant the entire area, but I had a little help from a friend. (Note: next year I am having an onion planting party!)

Mulching:

The area mulched with the spent grain equaled about 640 sf, and required approximately 1,700 lbs of wet spent brewer’s grain (SBG) mulch. This allowed me to mulch at a ½ inch depth.

I began mulching on May 27 with the spent grain and applied approximately 212 sq ft of SBG. As I mulched the designated treatment plots it became abundantly clear that Blind Bat Brewery was not able to produce enough grain for coverage to happen all at once, so another source was located. With an additional 428 sq. ft. still requiring mulching, I turned to another local brewer and friend at Long Ireland Beer Company in Riverhead.

Some observations: Wet brewer’s grain is stinky…especially as it ages. The spacing of 8″ was a blessing because it makes applying the grain much easier; closer spacing would have made it more difficult because my goal was to keep the grain away from the base of the onion plants by about a 1/2 inch.

Application of the grain for this project was manual and took me 5.25 hours for the total area of 640 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 and consistent application proved to be difficult.

The depth of grain was approximately 1/2 inch, and I had hoped to add to it as time went by to attain a 1″ depth, but was unable to actually achieve that because between the time I put the first batch down and then the second, the weeds had already started to grow. Not wanting to disturb the grain I put down by pulling the existing weeds, I left the depth at ½ inch.

After mulching the area with spent grain, I ran the overhead irrigation system for 45 minutes to settle the mulch down and to minimize the smell, which unfortunately smells something akin to puke.

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

Straw mulch was put down on June 9 and took approximately 3.5 hours for the total area of 640 sq. ft.

Weeding:

I began weeding the plots on June 24 and weeded the entire area once over the course of two weeks. Weeding and weighing was quite time consuming, taking about 8.5 hours, and was heavy and dirty work. I was unable to weed all of the treatment areas at one time, so I did it piecemeal and weeded on 6/24, 7/2, 7/7, 7/9 and 7/11. Two of the repetitions (Row three and Row four) were weeded on 6/24 and the count for these weeds were recorded, but between my first weeding session on 6/24 and the next on 7/2, I completely forgot to count the weeds, so weed count data is incomplete for Rows one and two. With the farming season in full swing, the weeding aspect of the study was unintentionally neglected. In total, I “harvested” over 482 lbs of weeds.

Observations: Of note is that the treatment using spent brewer’s grains yielded weeds of less diversity: mainly Pigweed, Purslane and Crabgrass; with the Pigweed and Purslane being extra large and succulent. The control area (i.e. un-mulched) had a much wider range of weed types, including: Pigweed, Purslane, Hairy Galinsoga, Pennsylvania Smartweed, Field Pennycress, Chickweed, Henbit, Barren strawberry, & Bittercress. The treatment area mulched with straw had some Pigweed, Purslane, but mostly Oats, which appeared to originate from the straw itself.

Also of note was that I saw lady bug nymphs here and there on the pigweed. Also in the SBG treatment areas, the pigweed had a lot of wooly aphids…perhaps a result of the high nitrogen content contributing to the outrageous growth. Insect pressure seemed fairly minimal, until the last session of weeding in the SBG treatment area, where the mosquitos were wild! (Cilantro geranium leaves worked great to keep them away, so I rubbed my neck with them and stuck a couple of sprigs behind my ears.)

Weeding the SBG treatment areas really disturbed the mulch, and also because the weeds were pretty closely spaced to the onions, the green onions tops were often damaged in the process. This is especially true of the last weeding session on 7/7. Being unable to add more mulch, due to the density of the weeds in the area that remained un-weeded probably resulted in even more weeds emerging. The rate of weed growth in the areas mulched with spent grain is a consideration I didn’t factor in.

Harvesting:

I was able to wrap up all of the onion harvesting at Fox Hollow Farm and the weights and counts are noted in the table below. Because I was not sure about the status of my study, I did get the broccoli starts going anyway. Many of these starts were donated to Cornell for a study they were conducting, some were given to friends and others were planted in my home garden.

To keep track of the different treatments the onions were being pulled from, I used index cards with detailed info about the treatment area (SBG, Straw, Control) and if it was weeded (weeded, not weeded) and wrote weight and number count on back. I also took photos of the different harvests for a visual feel for the harvest.

Even before actually doing statistical analysis and just through observation, it appeared that the onions did best in the straw treatment. This was true even in the areas that were not weeded. The SBG treatments areas yielded fairly large onions, too.

Of note: when I started to harvest Row 4 Control (not weeded), it was obvious that the plants had no chance against the Pennsylvania Smart weed that engulfed them. The few I had tried to harvest appeared to not change in size at all from when they were planted.

All together, I harvested 1,019 harvested Marble Cipollini Onions weighing a total of 91.97 lbs and 1, Ailsa Craig Exhibition Onion weighed in 236.7 lbs. These total included any greens left on the plant, though most of the foliage had dried back to the bulbs.

Detailed harvest data is noted in the table below.

• Harvest Data

Impacts and Contributions/Outcomes

JMP Statistical Software was used to analyse the data. Please see SARE Grant Table file below.

Conclusions:

1) There were no significant differences in the weeding weight or weeding time among the control, SBG, and Straw plots. However, these values were greatest for control and least for the straw treatment.

a) A significant difference in the weight of the Red Marble harvests from the weeded straw plot was found in comparison to the control (not weeded), but not to the SBG whether it was weeded or not. There were no significant differences between the SBG (weeded or not) and the Control Plots (weeded or not).

b) A significant difference in the weight of the Ailsa Craig harvest from the weeded straw plot was found in comparison to the Control plots (weeded or not), but not in comparison to the Spent Brewer’s Grains (weeded or not) or the un-weeded Straw plot.

c) There was a significant difference in the weight of the Ailsa Craig harvest between the weeded Spent Grain Plot (for Ailsa Craig) was found in comparison to the un-weeded control plot.

Observation A suggests that even if using straw, weeding is needed to make a significant difference in yields in (at least) the Red Marble variety, and that spent grain, apart from being a less expensive option did not effectively suppress weeds in terms of yields.

Observation B also suggests that for best results, straw, along with occasional weeding will result in better yields in the Ailsa Craig Variety, and that SBG was not effective in weed suppression. As noted with the straw treatment, it appears that additional weeding might be of benefit in addition to mulching with spent grain.

Observation C suggests that similar to straw that spent brewers grain mulch is most effective when supplemented with some weeding.

Discussion:

Though the data suggest that Spent Brewery Grain is not an ideal weed suppressant, a repeat of this study with correct depth of one inch application of spent grains, along with earlier and more regularly scheduled weeding might yield more favorable results with spent grain vs. straw mulch.

A more significant difference between the treatment plots and the control plots for the Ailsa Craig variety may indicate that the mature onion size is of importance when working with SBG. As noted earlier, next year’s experiment will include storage onions with an anticipated similar approximate size at maturity.

Other benefits to using SBG as a mulch have been noted through informal observation, including an increase in the number of earthworms, somewhat more crumbly soil texture, suggesting improved drainage, and because of the high level of cellulose in the SBG added stable organic matter. I also found a garden snake in one of the plots mulched with SBG, which suggests that it provides a beneficial environment for larger beneficial organisms as well as a predatory insects such as lady bugs. Finally, since the straw purchased cost $7.50 a bale, and then also required labor to apply, the cost-free nature of the SBG could also be of benefit to a farmer with a tight budget.

It should also be noted that the sun exposure to the area that was planted was not as abundant as I was advised it would be and while it was amended with plenty of organic matter, drainage was somewhat slow. These two factors may have significantly affected the growth of all of the onions for this project, but in particular for the onions where SBG was used as a treatment, water retention could have prolonged due to the initial wetness at application time and affected the development of the onions, particularly the Red Marble Cipollini variety. (See number of onions harvested as compared to planted in the Harvest Data section.)

• Use one variety of onion, or at least of the same size and maturity date (the Red Cipollinis were likely not able to handle the amount of grain put upon them, as noted by the number of plants that simply disappeared from the treatment plots)

  Ensure that the sunlight is equal among all areas (Trees at the south side of the field in this year’s study plot created more shade…an issue with other crops as well)

  Plant onions seedlings of consistent size (When planting the first row of onions, I planted all of the onions no matter what size; as I saw that I would have more than enough, in the second, third and fourth replications, I chose a minimum size and planted those and larger.)

  Order plants and don’t try to grow them myself; that way I’ll have the number I need without worrying.

  Order a storage onion variety; if using two varieties, choose similarly sized onions.

  Build a jig! Dibbling nearly 4,000 holes is tiring and probably caused some shoulder trauma as well. (Ideally, I’ll find a way to make a “roller” with the dibbles spaced at 8″ each.)

  Get a planting party together.

  Put all the grain down at once in one area at 1″ and do it fast. SBG is really putrid smelling after hanging around a few days.

  Weed more regularly, perhaps with hired help, and when weeds are still small. Pulling large weeds greatly upset the SBG and likely allowed more weeds to invade more quickly.

  Consider replenishing the SBG after transplant of the Broccoli as harvesting the onions will likely cause great disturbance of the existing SBG.

  Keep a log of when the field was irrigated

  36” beds will be sufficient for 4 rows of onions.

Outreach is planned at the conclusion of the study, but I have been adding details of the study as it progressed on my blog (http://farmersgrant2012.blogspot.com/) and website (http://seedsowerfarm.com/blog-2/).

• Data Analysis

Collaborators: