Abstract

Solutions to the problem of high-cost, unsafe, and non-sustainable commercial agricultural fertilizers will involve finding soil fertility methodologies that are:

• Effective: As effective as their commercial counterparts (if not more so)
• Low-cost: Solutions with minimal or preferably a one-time investment that is not reliant on industrial systems
• Sustainable: Solutions used to increase soil fertility and crop yield incrementally over time with repeated usage. A solution that "builds soil" with residual effects that are beneficial and not harmful to the environment.

A possible solution to the problem of commercial fertilizers could be using Aerated Compost Tea (ACT) during the growing phase of crops.

What this Study Does

This study observes and measures the effects of ACT on the:

• Germination
• Growth 
  • Weight
  • Yield
• Nutrient Density (measured in NDS / Nutrient Density Score developed during the course of this research)

Of Swiss Chard (Beta vulgaris L. var. cicla),
Lettuce (Lactuca sativa), and
Kale (Brassica oleracea var. sabellica)

in a 3-month growing season.

What is Aerated Compost Tea (ACT)?

Aerated compost tea, or ACT is the cultivation of the diversity and biomass of beneficial aerobic microorganisms in the soil through the suspension of compost in an aerated water solution, which includes trace amounts of bacterial food in the form of molasses and fish emulsion (Morgan, 2017). 

The finished solution is applied to the crop's soil as a root drench and sprayed on the leaves of the plant

What are the Benefits of Aerated Compost Tea if Proven a Viable Solution? 

If ACT is proven to be viable, its benefits would be the following:

• Lowered Costs for External Inputs in the Current System of Farming

Current costs for farmer fertilizer inputs have risen dramatically. 

"Several phosphate and potash fertilizer products have increased by 15-20 percent since late September, while the cost of anhydrous ammonia, urea, and other nitrogen fertilizer products have increased by approximately 50 percent in the past two months. The rapid increase in fertilizer costs is being driven by high global demand, very tight supplies of many fertilizer ingredients, and by shipping issues at U.S. ports." (Thiesse, 2022).

Unlike expensive chemical fertilizers, ACT requires no huge expense apart from the purchase of the following one-time equipment:

• A 5-gallon bucket 
• A 200-watt pump and hose
• A mesh from which to suspend compost
• vermicomposting worms for the creation of bacterially-rich compost or a plant-based thermophilic compost

Thus, ACT is not industry-dependent since the farmer can create compost tea on the farm from his or her production waste.

Neither does ACT require a lot of input in time. The ACT process can take as little as 10 minutes to set up, as long as a source of compost is readily available.

In this study, pathogen-free vermicompost serves as the main source of compost. This compost is created in situ and does not require external purchase or inputs aside from the optional purchase of red-wriggler composting worms (Eisenia foetida). 

• Similar or Improved Soil and Crop Fertility

ACT has been used as a crop fertilizer, soil amendment, disease suppressant, and foliar spray (Shaban & Fazeli-Nasab, 2015). It could play a threefold agricultural role in food production and negate the need for additional soil amendment or foliar spray products.

It introduces higher concentrations of microbial populations into the soil to increase their diversity and number. An increase in beneficial microbial life in the soil correlates with an increase in soil fertility (Ingham, 2005).

This microbial life, in turn, increases water retention and improves soil tilth or structure.

The liquid nature of compost tea allows it to seep into the soil and "harder-to-reach" areas without much effort from the farmer.  

If proven viable, ACT could lead to similar or better crop fertility, growth, and yield. This would mean better production without costly inputs and chemical detriments to the environment and human health.  

• Increased Nutrient-Density in Crop Production

If proven viable, another benefit of using ACT in crop production would be an increase in the nutrient density of the crops we grow.

Nutrient density in plants in this study is measured by comparing 21 key nutrients needed for optimal plant health.  Because the data also provided certain heavy metal toxins found in plant leaf analysis, toxins were also taken into account and lowered the NDS score when present.

What are the Benefits of Studying the Effects of ACT on Swiss Chard, Kale, and Lettuce?

In this study, Swiss chard (Beta vulgaris L. var. cicla), kale (Brassica oleracea var. sabellica), & lettuce (Lactuca sativa) were chosen as crops due to their longer growing season in Virginia.  

As such, they provide a more extended harvest season and longer-term potential income for the farmer throughout the year. 

Another reason to study compost tea in the growth of these vegetables is that there are not many studies on the effects of compost tea on foliation.  Instead, most studies deal with disease suppression.  It would be good for farmers to understand the specific uses compost tea applications hold for different vegetables and at different seasons of the year.  This study on leafy greens sheds light on one type of vegetable that is underrepresented in the literature.

Proposed Solution

I propose a study measuring the growth, yield, and nutrient density of Swiss Chard (Beta vulgaris L. var. cicla), kale (Brassica oleracea var. sabellica), & lettuce (Lactuca sativa) grown with and without ACT to discover whether or not ACT could outperform or match the results found by the use of commercial fertilizers.   

The benefits of such a solution would be:

• Lowered Costs for External Inputs in the Current System of Farming
• Similar or Improved Soil and Crop Fertility
• Increased Nutrient Density in Crop Production

Conclusion

The results from the study revealed distinct outcomes across the three crops studied and general outcomes such as:

General Outcomes

1. ACT benefits specific crops.  While this study allowed for limited crop testing, the testing performed showed that ACT could be more beneficial when used on certain crops, and not necessary on others.
2. The study also revealed that contrary to previous literature and teachings on aerated compost tea, compost tea microbiome diversity dropped significantly after six hours of brewing.  Microbiome bacterial counts however did multiply for about three main bacterial families, suggesting that the aerated composting process selects for specific bacterial families and amplifies only a few families.  This is in contrast to previously held teachings and beliefs that compost tea aeration amplifies all beneficial bacteria counts.

Distinct Outcomes

 
LETTUCE
ACT-treated lettuce, as well as Control, displayed the highest Nutrient Density Score (NDS) among treatments.  ACT-treated lettuce also had the lowest toxin scores when compared to the other treatments, suggesting ACT could be a potential nutrient-enhancing treatment as well as a toxin-lowering treatment

SWISS CHARD
However, in Swiss chard, N-treated samples demonstrated the highest Nutrient Density Index (NDI)

KALE
In kale, the ACT treatment achieved the highest yield, Nutrient-Density Index (NDI), as well as the biggest root development.

Conclusions about ACT’s Effects on Leafy Greens (Swiss chard, Lettuce and Kale)

In this study, ACT made kale more nutrient-dense. In lettuce ACT affected nutrient density just as much as the control did.

ACT also seemed to increase the yield or number of plants harvested in Swiss chard and kale

ACT treatment was not helpful for seed germination.

ACT also did not help Swiss chard in terms of growth and nutrient density as the N-treatment did, which may suggest the benefits of ACT are crop-specific. 

• Does ACT exhibit Similar or Improved Soil and Crop Fertility?
  In this study, ACT treatments exhibited similar and improved soil and crop fertility for lettuce and kale but not for Swiss chard
• Does ACT increase Nutrient-Density in Crop Production?
  In this study, ACT treatments showed comparable nutrient density in lettuce and kale to their commercial counterparts but not in the case of Swiss chard
• Does ACT have lower costs for external Inputs in the Current System of Farming
  Yes! In this study, ACT costs include a one-time investment in a pump, bucket, and red wriggler worms, equivalent to ⅓ the cost of the Nitrogen application throughout the course of this project.

It is important to note that the number of treatments to measure nutrient-density in this study does not make the results statistically significant and further research and funding is encouraged as nutrient-testing is costly.  

Compost Tea Microbiome Findings

This study primarily aimed to assess the impact of Aerated Compost Tea (ACT) on plant growth and soil health. While achieving these objectives, an unexpected yet significant observation was made. The research revealed that the brewing process of ACT led to a notable decrease in microbial diversity, as indicated by the Shannon Diversity Index and the Krona Graphs, when compared to the original vermicompost.

However, this reduction in diversity was accompanied by the selective amplification of specific beneficial microbial groups, including potential Plant Growth-Promoting Rhizobacteria (PGPRs) such as Pseudomonas and Acinetobacter. These organisms are known for their roles in nutrient solubilization, phytohormone production, and disease suppression.

This dual outcome presents a nuanced perspective: while lower microbial diversity might reduce ecological resilience, the targeted increase in PGPR populations could enhance ACT's functional benefits for disease control or plant growth. This finding was not anticipated in the original research design but opens a promising avenue for future studies. Further investigation is needed to determine optimal brewing practices that maintain microbial diversity while promoting the growth of beneficial bacterial communities, thereby maximizing the agronomic potential of ACT as a sustainable alternative to conventional fertilizers.

The microbial outcomes in vermitea vs. vermicompost, mirrors patterns seen in other tests run by the Aggrego Data lab of Dr. Zack Jones (Aggrego Data) as well as other vermimposters who have DNA tested their vermicomposts and vermiteas. These systems also show a shift from microbial diversity to functional dominance, of a few key bacterial players, which offer disease resistance and nutrient cycling benefits.

Together, these findings support the broader conclusion: when carefully brewed, Vermitea can be an effective, low-cost, and sustainable biofertilizer alternative, providing the same amount of beneficial bacteria when compared to commercial offerings, competitive plant health and nutritional benefits while reducing reliance on industrial inputs.