Farm Duckweed Harvesting

Project Overview

FW07-008
Project Type: Farmer/Rancher
Funds awarded in 2007: $8,519.00
Projected End Date: 12/31/2009
Region: Western
State: Washington
Principal Investigator:

Commodities

  • Animals: poultry, swine

Practices

  • Animal Production: feed/forage
  • Crop Production: nutrient cycling, tissue analysis
  • Education and Training: extension, farmer to farmer, on-farm/ranch research, participatory research
  • Natural Resources/Environment: habitat enhancement

    Summary:

    INTRODUCTION

    JJJ Farms is a family farm located in the temperature climate of the Washington Puget Sound, near Kingston. Our primary product is pork, with a secondary market in poultry

    We have an approximately 1-acre pond in the southwest corner of our farm. The pond is planted and protected for wildlife habitat, with a small island in the center. While vegetative strips protect the pond from sediment buildup, soluble pollutants, mainly nitrate and phosphorus, do collect in the pond during runoff months. The pond is seasonal, and, while containing water year round, out flow stops during the dryer season. The pond is also used for pasture irrigation, and it varies in depth from about 4 feet to 8-12 feet at either end.

    While many aquatic plants are great reservoirs of nitrogen and phosphates, only by removing these living plants from the pond do you reduce the pollutants. If left to die and decay in the pond, the pollutants are released back into the water.

    In July, we had a sample tested for feed content, and while duckweed is 96% water, the resulting 4% was 41.38% protein, 2.3% fat, and 16% crude fiber – pretty high quality feed, after the water is extracted.

    OBJECTIVES

    The purpose of this project is to see if harvesting duckweed (Lemnaceae), a floating aquatic plant, as a supplemental animal/poultry feed can have an impact on reducing soluble nitrate and phosphorus in runoff water and serve as a supplemental animal feed.

    RESULTS

    We started aeration in spring 2007 using an existing 5 cfm air compressor, aerating the pond in 3 different zones at rotating time intervals. Water testing began in July of that year, at the cessation of outflow from the pond and continued through the duckweed harvest season of 2008.

    In fall of 2007, using the SARE’s funding, we were able to upgrade the air compressor to a 15 cfm unit. While this upgrade did show a small appreciable difference in water quality testing, especially in the nitrates, it did greatly increase the duckweed harvestable tonnage. In 2007, we harvest 3,653 pounds. In 2008 we harvested 7,096 pounds, a 49% increase in usable livestock and poultry feed.

    CONCLUSIONS

    Using a small to medium air compressor to aerate and agitate pond nutrients for a duckweed-growing medium is a viable option. Duckweed is a highly nutritious supplemental livestock/poultry feed. While harvesting is labor intensive, if the crop is growing well, a day’s feeding can be harvested in a relatively short time, and other than rinsing, no other preparation is necessary.

    We harvested 5.37 tons of alternative feed for livestock and poultry during 2007 and 2008. As a “by-product” of this feed, we have significantly cleaned up our pond.

    Duckweed feeding will continue for years to years to come on JJJ Farm, and will be incorporated into our feed management plan.

    RECOMMENDATIONS

    If using pond for irrigation, try to irrigate then aerate. The aeration system will push the duckweed to the sides of the pond. If the water level drops during aeration, some duckweed will be trapped on the pond side.

    Duckweed will multiply about 40 times before dying out. As it ages, it will turn pale green/yellowish. This will appear as “streaks” or “splotches” of lighter colored material in the pond. There is nothing wrong with it, it is just getting past reproductive age. Scoop and feed these as they appear to keep younger plants reproducing.

    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.