Using invasive Eurasian milfoil as an organic soil amendment: Effect on tomato yield

Final Report for FNE14-791

Project Type: Farmer
Funds awarded in 2014: $6,697.00
Projected End Date: 12/31/2014
Region: Northeast
State: New York
Project Leader:
Brittany Harris
Fledging Crow Vegetables
Co-Leaders:
Ian Ater
Fledging Crow Vegetables
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Project Information

Summary:

The “Using Invasive Eurasian Milfoil as an Organic Soil Amendment: Effect on Yield of Tomato Crop” project aimed to identify the effect of low and high does treatments of Eurasian Milfoil on tomato yields as compared to a control group. In a randomized block experiment in a 96” by 24” high tunnel, we created 12 experimental blocks (each measuring 20” by 3”), and randomly assigned one of 3 treatments to each block. The treatments were applied as a mulch. The treatments were, (1) high dose of Eurasian milfoil; 10 gallons of moist milfoil per 60ft2 block, (2) low dose of Eurasian milfoil; 5 gallons of moist milfoil per 60ft2 block, or (3) control; no milfoil applied.  We then carefully measured yield of the 15-20 plants in the middle of each block all season long.  Yields were not statistically significantly different between high dose, low does, and control groups.  The actual total yield of tomatoes in the High Milfoil Dose zones was 552.02 lbs, as compared to 570.99 lbs in the Low Milfoil Dose zones and 609.09 lbs in the Control zones. 

We believe this is due to the way the milfoil was applied, as a mulch instead of as a soil amendment. In the past , we have had anecdotal evidence of success with milfoil used as part of our composting system. We believe that the beneficial properties (if any) of the milfoil mulch was not available for uptake by the plants in the way it was applied.

Introduction:

Fledging Crow Vegetables is an 18-acre Certified Naturally Grown vegetable farm in Keeseville, NY. It has been in operation since 2008 and supplies a 400-member CSA program, as well as wholesale accounts and 4 weekly farmers’ markets. Due to the high levels of production, we are constantly seeking new ways to replenish nutrients in our soils and improve soil structure. Our research project aimed to explore the viability of Eurasian Milfoil as an inexpensive organic fertilizer that can be locally sourced.  Eurasian Milfoil (EM) is an invasive aquatic species that consistently out-competes native vegetation and quickly spreads to form dense mats on lake bottoms that degrade water quality and interfere with water recreation. We originally set out to test the effectiveness of Eurasian Milfoil (Myriophyllum spicatum) when applied as a soil amendment, but due to timing difficulties we ended up applying the EM as a mulch.  Our technical advisor, Amy Ivy, was the Executive Director of Cornell Cooperative Extension and she was instrumental in the experimental design and she took all of the soil and foliar samples during the project. Ian Ater, Brittany Harris, and Ross MacFarland carried out the experiment, including weighing yields from the tomato plants twice weekly for eleven consecutive weeks.

Project Objectives:

The objectives of this study were to:

  • Determine the effect of EM amendment as a soil fertility management practice by measuring yield of tomatoes with and without the amendment.
  • Use foliar nutrient tests to determine whether plant nutrient levels increase with the application of EM

Cooperators

Click linked name(s) to expand
  • Amy Ivy
  • Ross MacFarland

Research

Materials and methods:

The “Using Invasive Eurasian Milfoil as an Organic Soil Amendment: Effect on Yield of Tomato Crop” project aimed to identify the effect of low and high does treatments of Eurasian Milfoil on tomato yields as compared to a control group. Brittany Harris (Coordinator) carefully managed the measurement of tomato yield throughout the growing season, and Amy Ivy (technical advisor), aided in experimental design and oversight, and took foliar and soil tests. 

We learned that milfoil is not available until June, when temperatures rise in the Northeast and milfoil grows in the lakes.  The tomatoes are transplanted into the greenhouse in April, so we were not able to work the milfoil into the soil as planned. Instead, we applied the milfoil as a mulch around the tomato plants and placed drip irrigation on top of the milfoil to see if any nutrient would be added to the soil that could in turn increase tomato yields. 

In a randomized block experiment in a 96” by 24” high tunnel, we created 12 experimental blocks (each measuring 20” by 3”), and randomly assigned one of 3 treatments to each block. The treatments were applied as a mulch. The treatments were, (1) high dose of Eurasian milfoil; 10 gallons of moist milfoil per 60 ft2 block, (2) low dose of Eurasian milfoil; 5 gallons of moist milfoil per 60 ft2 block, or (3) control; no milfoil applied.

We then carefully measured yield (in lbs. of ripe tomatoes harvested) of the 15-20 plants in the middle of each block all season long (July 2014-September 2014). Yields were not significantly different between high dose, low does, and control groups. We believe this is due to the way the milfoil was applied, as a mulch instead of as a soil amendment. In the past, we have experienced anecdotal evidence of success with milfoil used as part of our composting system. We believe that the beneficial nutrients from milfoil (if any) was not available for uptake by the plants in the way it was applied. In the future we would like to study milfoil’s effect on the soil, rather than on its source as a nutrient, but that will be another experiment entirely.

 

Research results and discussion:

The milfoil applied as mulch provided little nutrient value to summer crop of high tunnel tomatoes. It did not increase yield; in fact the control plots had a higher overall yield than either of the two treatments. The total yield of tomatoes in the High Milfoil Dose zones was 552.02 lbs, as compared to 570.99 lbs in the Low Milfoil Dose zones and 609.09 lbs in the Control zones. 

Foliar nutrients level were lower August after the milfoil application than in June before the application, but that is to be expected since August is the period of maximum fruit load and nutrient use by the crop. 

The time of application of the milfoil was not ideal in terms of providing a nutrient benefit. Tomatoes need to be planted in late April-early May but milfoil is not available until June. The supply was limited this year, with only one application possible. The foliar nutrient levels were statistically the same between the 3 treatments, indicating that the milfoil did not have an effect.

 

Tests conducted:

6/20/14 – pre milfoil application foliar nutrient analysis of 4 quadrants of study area

8/10/14 – post application foliar nutrient analysis of each of the 12 treatments

11/24/14 – dry sample of milfoil foliar nutrient analysis

 

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary:

Education/outreach description:

The results of our experiment did not prove very useful to other farmers. As a result we have modified our outreach plan. We worked with Amy Ivy to write an article for the Eastern New York Commercial Horticulture Program Newsletter. The article is a "lessons learned" piece that instructs farmers interested in using milfoil to apply it to their compost piles or work it into their fields experimentally, instead of appling it as a mulch.

Project Outcomes

Assessment of Project Approach and Areas of Further Study:

Future Recommendations

More research is need to see what benefit, if any, Eurasian Milfoil can provide to soil nutrient and structure on vegetable farms. If growers have interest in using milfoil in the future, it is recommended that they experiment on working the milfoil into the soil or compost in the fall. This is due to the fact that milfoil is only available during the summer months when water temperatures in local lakes are high enough to support its growth.

Growers who have added milfoil to their compost or worked into the soil before planting feel it has a benefit. To study this more fully milfoil will need to be stockpiled in advance and then worked into the soil in significant amounts before planting in a replicated trial to see if it enhances root growth and therefore plant growth. It may well be that the key benefit milfoil provides is as a renewable source of organic matter to improve soil health. This could be a significant benefit and further study to determine optimum rates would be very useful.

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.