On farm research allows growers to evaluate compost tea as an Integrated Pest Management practice
Published in the March 2001 BioCycle
Lisa Wickland, Todd Murray & Joyce Jimerson
Pressure to reduce pesticide usage, recent awareness of alternative controls, combined with a marketing trend towards natural cure-alls can tempt farmers into unreal expectations. The farm is a living lab. Its environment is vital, the conditions variable, and each farm influences natural control practices in specific ways according to a farm's distinctive environment. Many natural controls are not pesticides, these are living communities, and the success of a well-versed integrated pest management program depends on the farmer's continual involvement and watchful eye.
Integrated Pest Management (IPM) is a problem-solving process using multiple control strategies in concert with one another. IPM consists of pest identification, threshold determination, pest monitoring, 'least toxic' management decisions, record keeping and finally, evaluation. Many growers overlook the evaluation process of IPM. University researchers traditionally provide reliable recommendations for pest problems. However, in a time when growers are inundated by new management strategies, the plethora of snake oils and silver bullets challenge individual growers to judge useful management practices for themselves. For an additional challenge, many preferred IPM strategies, such as biological control, are still in their early developmental stages and are not yet fully understood by the academic community. Growers have limited reliable information to base decisions on. This is why on-farm research is paramount.
Why Growers Make the Best Researchers
Research in agriculture has to be useful, relevant and practical. Who else knows what growers need than growers themselves? Who else understands the real life scenery of agricultural production than the farmers? Who else can understand the limitations of new management strategies than those who live it daily? Growers need to be involved with the development of new technology and research. There are many resources available to help assist in on-farm research. Cooperative Extension, research universities and private consultants can provide much of the know-how of experimental design and give a hand in the interpretation of results. There is even money available to support on-farm research. The purpose of sharing this article is to exemplify the process of on-farm research in hope that growers, pest managers and compost users will use these standard methods to critically evaluate their practices.
What is Compost Tea?
Compost is like a rainforest of soil organisms, a diverse microbial community. Compost tea is exactly like it sounds… as if you brewed tea, only with compost in the tea bag instead. In other words, compost tea is a water extract of compost. Compost tea production dates back to ancient times. Traditionally, people made tea in buckets or large containers with hand stirring action to bring in oxygen. Now, there are newfangled brewers that keep the tea continually oxygenated. Theoretically, beneficial microorganisms would reproduce better and be more abundant in an oxygenated environment. Tea made without the oxygenation process could become anaerobic, which would mean different kinds of organisms would grow and potentially produces organic acids detrimental for plant growth.
Maturity, composition and the environment of compost are major factors for determining the fate of the microbial community in the tea. Temperature, brewing length, method, timing and frequency of application, and weather conditions all play a large part in the final tea results. It is important to keep these factors as consistent as possible. Although no one has control over sunshine, the type of compost used, brewing and application methods can be monitored.
Teas can be brewed in various ways as well as with different ingredients. For mechanical tea brewers, manufacturers suggest vermicompost compost, kelp and molasses be added with water. These additional components offer food and nutrients for microbes in the tea and may benefit plants. Vermicompost is used because of its biological value, consistency, and availability. Vermicompost is a mixing and ingestion of organic material by worms, which encourages an aerobic mesophyllic environment. The mechanical brewers hope to continue this environment. Up here in Whatcom County, we have the pleasure of a large amount of separated dairy manure, which is perfect for feeding worms. Pacific Garden Company is taking advantage of this resource to produce quality vermicompost.
Why use it?
There is a growing interest in the use of compost tea as a disease inhibitor due to its concentration of beneficial microbial organisms. Many growers are trying to reduce their use of conventional pesticides with various alternative pest management methods. There are many microbial components that enhance plant growth and aid disease suppression, including: bacteria (Bacillus), yeasts (Sporobolomyces and Cryptococcus), and fungi (Trichoderma), as well as chemical antagonists such as phenols and amino acids. In theory, by introducing a diverse microbial community to agricultural systems, beneficial microorganisms in compost tea out-compete destructive microorganisms for nutrients. This biological control practice is common in plant pathogen suppression. However, there is very little scientific data useful for growers, and few facts published about aerated compost tea.
Brainstorming and butting heads… Building a Hypothesis
In April of 2000, Whatcom County greenhouse grower Alison Kutz-Troutman of Cascade Cuts gave Cooperative Extension an opportunity to test the efficacy of compost tea as a valuable IPM strategy. The previous winter when she was considering a compost tea brewer purchase, Alison contacted the Cooperative Extension for any information or advice we might suggest. All that we could offer was personal anecdotal experience dating back 25 years, when it was a fad for gardeners in New England to make compost tea in five gallon buckets. There were also a few interesting research trials, but again, from the various bucket methods that were made without emphasis on aeration of the tea.
Although we could offer no proven benefits, Alison bought a brewer, and began conducting informal trials on her crops, seeing trends that she attributed to tea use. Alison noted that when applied to Cyclamen, she observed "a clear suppression of Fusarium (crown rot) in the crop." The control group was treated with two conventional applications of fungicide, and there was some incidence of Fusarium. "We found no Fusarium in the tea group, (which was not treated with fungicide)." They also saw suppression of Botrytis (gray mold) throughout the crop of French Lace scented Geraniums. One of the growers exclaimed: "This is the best crop of scented Geraniums I've ever seen!"Although we could offer no proven benefits, Alison bought a brewer, and began conducting informal trials on her crops, seeing trends that she attributed to tea use. Alison noted that when applied to Cyclamen, she observed "a clear suppression of Fusarium (crown rot) in the crop." The control group was treated with two conventional applications of fungicide, and there was some incidence of Fusarium. "We found no Fusarium in the tea group, (which was not treated with fungicide)." They also saw suppression of Botrytis (gray mold) throughout the crop of French Lace scented Geraniums. One of the growers exclaimed: "This is the best crop of scented Geraniums I've ever seen!"
While Alison showed optimism concerning the compost tea brewer's role in her operation, at Cooperative Extension, we were not as confident.
Todd Murray, the IPM coordinator for Whatcom County Cooperative Extension, rolled his eyes and turned up his ivory towered nose, "where's your data? How do you know you have control of your plant pathogens?"
Joyce Jimerson, Whatcom County Master Composter Program Manager, added cantankerously, "In my day, we just soaked compost in water. We didn't need to add air. It worked fine… and we liked it."
The idea of using oxygenating brewers to make tea was intriguing, and merited further research. Watching Alison's enthusiasm over her experiences with the brewer encouraged us to offer help to conduct standardized trials with the tea to see what, if any, difference compost tea could make on specific crops for specific diseases. We collaborated and conjured up a hypothesis. Todd wanted to scrutinize the efficacy of compost tea as an IPM strategy, Joyce wanted to see if anaerobic was different than aerobic teas, and Alison wanted to take her research to the next level with amendments to the tea. We needed to keep it simple. If more variables are added into the trials, it is more difficult to find answers.
The hypothesis stated, "there is no difference in the suppression of diseases that cause damping off in seedlings between weekly treatments of water, aerobic and anaerobic tea." We designed our experiment to test our hypothesis.
Know your enemy
To solve a problem, you need a problem. Then seek information to find a solution to that problem. Learn all the strategies of the enemy; where the mess hall is, where the troops hide out, and most importantly, what kind of artillery to use. Identifying the pest will provide a great amount of specific information. If the enemy is an insect, take samples to an entomologist, or if it is a disease, a plant pathologist can help. Different pests require different management approaches. Knowing about your pest also helps you know how to study it. Some pests are only active at specific times of the day and some are only susceptible during a certain stage in their lifecycle.
Alison explained her problems and walked us through the day-to-day life of her crops from seed to sale. She taught us the limitations and problems she faces to control her disease pressures. For her farm, ornamental basil crops sown in spring have difficulty battling 'damping off' diseases caused by Fusarium, Pythium, and Rhizoctonia organisms. On her farm, 'Siam Queen' is the most susceptible variety. This is the perfect problem to test. Many conditions and organisms cause damping off, so we periodically sent the plants off to have pathogens identified.
Decisions on Experimental Design
When deciding on an experimental design, you need to know what components of the environment affect your experiment. Locate your plots in an area where all factors are going to be as uniform as possible. For instance, setting up plots next to the door or by a fan will introduce unwanted variables. At the center of Alison's greenhouse, there is little variability in temperature, airflow, and watering conditions. For our experiment, we chose this site and a Completely Randomized Design. This design structure selects plots from a larger population and randomly assigns treatments to selected samples. It is a simple yet precise design used for research with uniformity throughout the test plots.
Figure 1--Completely randomized design showing 4 replication for the three treatments. Each square represents an individual flat with 24 pots per flat. Blue = conrol, red = anaerobic, green = aerobic.
How many plants do you need to make a valid point about the role of compost tea in disease suppression? As a general rule large samples paint a clearer picture. Your sample is a representation of what really happens on your farm. Does it make sense to base all your decisions on one row of corn, or one flat of plants? What happens when that flat is accidentally sold or the neighbor's cow eats your row of corn? Replication of your experimental treatments offers a safeguard against the unpredictable variations of everyday life.
In these experiments, we planted 2 (288 cell) starter flats with four to six basil seeds per cell. These flats were randomly separated into the different treatments and then different replications, and flagged with bright tape to distinguish them as trial starts. We started with 192 cells per treatment with 4 replications (48 cells for each replication). These were treated and placed in a controlled germination chamber for five days, then moved to a warm greenhouse for further development. They were monitored closely for disease every week starting with the second treatment, seven days after planting.
Two to three weeks later, we transplanted them into 3.5" pots with four-six plants per pot, totaling about 100 pots per treatment, with at least 24 pots per replication. Each pot was color coded with a sterilized toothpick, and each replication flat of 24 pots was marked with flagging tape and randomly placed on the floor of the greenhouse. After the plants were put into place, the entire site was flagged with bright tape and markers to ensure the trial plants were set apart from the rest.
Comparing Apples to Apples, The Importance of Consistency
Consistency is the most important factor in getting meaningful results from research trials. Don't get caught comparing apples to oranges. Plant the same variety, keep observations and sampling processes identical, and never change treatments after starting the experiment. The purpose of research is to see differences between treatments. If anything besides the treatment is different, the data could reflect these changes. To remain consistent, we randomly assigned treatments to basil plants, applied treatments the same time, same day every week, and the same person collected data. We kept the biases and unwanted variation at a minimum.
Don't forget to notify your staff about your research. It takes a matter of seconds for months of data to go out the window or off the farm. Labeling the site with "do not cross" police tape is a good idea. Workers may not be aware of the time and energy you put into the research, and efforts can be lost to accidental pesticide applications or premature harvest of the crop. We learned first hand when, without obvious markers, a few trial flats were sold and results were lost for that whole trial. This is always a problem in on-farm research but can be easily avoided with little effort. Simple communication and flashy tape can prevent this from happening.
Applying the Treatments
Our treatments consisted of a control, anaerobic and aerobic tea. The control was straight tap water. Anaerobic and aerobic tea shared the same ingredients, differing only in the brewing process. For the anaerobic tea, we soaked vermicomposted separated dairy solids, soluble kelp and molasses in a bag for 48 hours. The solution was strained and mixed with water to a dilution of 1:10. The aerobic tea was brewed in a large aerated container, developed by Growing Solutions. This extract was also diluted to the same ratio with water. The tea treatments began upon germination, and continued until the plants were ready for sale. 8 am Thursday was teatime. Applications were early in the morning to avoid UV damage to the tea (many organisms are sensitive to UV sunlight). A hand held atomizer was used to apply a 'sprench' (combined foliar and drench application) of tea, penetrating about ¼" into the soil. A plastic shield was put up between treatment plants to prevent drift of tea to other plants during applications. Consistency is of utmost importance; the application of treatments is what you are testing.
Measuring Up The Enemy
Armed with hand lenses, wax pencil and data sheets, every week we examined each plant within each pot for signs of damping off. A plant was diseased if the shoot exhibited symptoms of damping off. Indicators include a split stem, wilted foliage, visible dark brown rot at the soil line, and sometimes spore production.
Figure 2. Sample data sheet.
Although a noble job, data collection is tedious. To become a good data collector, be mechanical. Clear your mind and let your data collection sheets guide you through the plots, this will ensure the data samples represent what's really happening. Start at one end of the block and systematically evaluate each plant for each plug for each plot. Data collection needs to be consistent to avoid any biases in the results. Do not try and observe trends as you collect the data. Ignore the broken irrigation, barks over your walkie-talkie and nagging employees for the next few minutes and fill out the data sheet.
Statistics or Sadistics?
The dictionary describes statistics as the "mathematics of collection, organization, and interpretation of numerical data, especially the analysis of population characteristics by inference from sampling." What does this mean? It means you have collected data in a standardized and organized fashion that allows you to apply mathematical principles to interpret your results. This scientific method provides a known degree of reliability to your results and is factual instead of anecdotal. Often the most intimidating part of research is analyzing the data. Seek help; Cooperative Extension, universities, computers, the Internet and consultants can assist with data analysis and interpretation of results.
Three trials and seven months later, it was time to analyze the results. We opted to analyze our data with a computer program using one-way analysis of variance, with a least significant difference pair wise comparison of means. Although this sounds like a bunch of jargon, it is a method of analysis that provides you with the power to accept or reject your original hypothesis. It considers the number of samples and compares the normal variation within and between each treatment. The resulting magic number tells us whether treatments differ significantly, known as significant difference.
What did our data tell us? Over all, the data was inconsistent. In two of the three trials, we found a significant difference between weekly treatments of water, aerobic tea, and anaerobic tea in the suppression of damping off in seedlings. Although there was a greater incidence of disease in the control plants than both aerobic and anaerobic teas, statistical differences did not occur until 6 to 8 weeks after germination. Thus, when compost tea works, it takes some time to see the results. We found no statistical difference between the bucket-type and the new oxygenated brewing method of tea.
Figure 3. The graph depicts average percent of healthy plants withing each treatment for each trial. *Significant difference between the presence of disease in control plants and that of both aerobic and anaerobic compost tea. **Trial lasted considerably fewer weks due to loss of sample plants.
To Tea or Not to Tea?
Even though some of our results are statistically significant, the practical benefits of using compost tea to suppress root diseases may be marginal. In our research, we did not see an extreme amount of disease suppression as we observe when experimenting with traditional pesticides. Using tea as a reliable amendment is difficult since benefits are contributed through many factors instead of known active ingredients, like pesticides. Unlike many other types of cultural amendments or pest treatments, compost is comprised of a very large and diverse community. The community dynamics of compost tea is not understood or currently controllable.
Integrated Pest Management selects the least disruptive, scientifically proven method of control. IPM is not a strategy decided with tunnel vision, IPM practitioners consider many factors when evaluating a management strategy. Economics, markets, efficacy, and duration of the management practice are important along with the interests of and impacts on society, human health, non-target organisms and the environment.
Is Cascade Cuts satisfied with integrating compost tea in its IPM program?
"ABSOLUTELY. Growers need to determine what is economically feasible for them in their particular setting, whether evaluating a chemical product, or natural supplements such as compost teas. It (the experiment) enabled us as growers to evaluate crops in a subjective manner… We had some really obvious successes with the tea."
She was philosophical about this on farm trial and recognizes the need for growers to do more research: "the basil studies raised more questions than gave answers. That is alright-and understandable. The whole field of microbiology seems to be in its infancy-we need more testing methods and much more information about what we are actually looking at."
For this farm, compost tea is good to the last drop.
Lisa Wickland is a technician for the IPM Project at Washington State University Cooperative Extension in Whatcom County. Todd Murray is the IPM Project Manager and Joyce Jimerson is the Master Compost Program Manager, WSU Whatcom County. Please visit our website http://whatcom.wsu.edu/ for more information on Composting, IPM and On-farm research.
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