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Mulching with Wool

Mulching With Wool: A Sustainable Method For Organic Farmers

by Katherine Charlton-Perkins & Melinda O’Briant of Cincinati, OH

Organic agriculture has its challenges for every farmer. Many farmers find unique approaches to deal with specific problems that occur on their farms whether they be pests, weeds, irrigation, or labor costs. Bonnie Mitsui of Turner Organic Farm, located in Cincinnati, Ohio, identified a problem of unwanted wool resulting from the production of lamb for meat. The problem at Turner Farm reflected a growing issue with the accumulation of sheep wool by many regional wool-growers and a non-existent market for the sale of imperfect wool. To maintain their sheep herds for lamb production, Turner Organic Farm typically shears 40 ewes and three rams annually, resulting in the accumulation of 260 pounds of raw, unsalable wool per annum. This unsalable wool is referred to in the industry as “kempy” wool.

The situation at Turner Farm is a small-scale representation of a larger problem facing many wool growers in Ohio today, as confirmed by the Ohio Wool Growers Association and the Mid State Wool Growers Cooperative Association. The accumulation of unsalable wool from the production of lamb for meat increases overall storage needs and overhead costs. The reason many wool growers store this kempy wool is simple; there is no existing market for kempy wool, as it has no textile value, and thus is considered an agricultural waste. During the 2010 growing season the price of kempy wool was seven cents per pound.

Mulching with Wool

At Turner Farm, Bonnie Mitsui and Melinda O’Briant, Garden Manager, resolved to address the wool storage problem by using the wool as a mulch in vegetable production. Melinda hypothesized that the wool would help to control flea beetle; one of Turner Farm’s most persistent pests in eggplant production. She hypothesized that the flea beetle, which breathes through tiny holes known as spiracles, might suffocate due to the lanolin in the wool. It was this initial hypothesis that spurred Bonnie Mitsui and Melinda O’Briant to approach me requesting that I conduct initial preliminary experiments testing kempy wool as a mulch in eggplant production. This initial experiment allowed me to apply my training in ecology and environmental science to agriculture. I was delighted to have the opportunity to conduct on-farm research that might be beneficial to other farmers. In our initial trial we applied the wool to the rows as entire fleeces and parted the wool around the base of the plants. The wool was roughly four to six inches in thickness, and we spread it over four foot rows. It matted down slightly after rain events, however, seemed to keep its overall density as a mulching material. The soil under the wool was cool and moist. It also seemed to support a diverse microbial habitat with a fluffy and aerated tilth.

By the end of the 2010 summer growing season, the results of the initial experiment were so stunning that applying for a USDA Sustainable Agriculture Research & Education (SARE) Grant was the next step. Black Beauty eggplants mulched with kempy wool grew taller and yielded significantly more than eggplants mulched with hay. It was also remarkable that in the 2010 growing season a drought occurred and the eggplants mulched with wool were unaffected. Although the flea beetle damage was still observed on eggplants mulched with wool, the plants were visibly more resistant to the pest than plants mulched with hay. In our preliminary trials, we also noted that there were many complex environmental variables at play in conjunction with the application of wool mulch. The plants which received the wool treatment were significantly taller and darker in leaf coloration. The dark leaf coloration suggested that nitrogen was somehow more available to the plants mulched with wool. Although the flea beetle did not seem deterred, the plants were much more resistant to this stressor and appeared healthier than the samples mulched with hay. Row weight and number data suggested that the plants mulched with wool were more productive as there was a significant difference in row weight and number between the two treatment groups. We also noticed that the soil surface under the wool felt dramatically cooler and seemed to have better moisture retention than that under the hay mulch. After the initial experiment, we raked the wool and composted it. It can take up to two years for wool to fully break down. We believe that wool can be reused, or perhaps even left on the soil as long as plants are being rotated in order to not spread diseases to susceptible plants such as tomatoes.

Mulching with Wool

Upon applying for the grant, acquisition of funding was successful to repeat the experiment in more depth in the 2011-growing season. Prior to receiving the USDA SARE Grant in 2011 the price of wool was seven cents per pound. One of the many goals of the grant was to create a market for kempy wool, so the grant paid 25 cents per pound to wool growers, and allowed Turner Farm to purchase additional wool as the in-house amount was not enough to cover the large scale experiment which was proposed. As part of the USDA SARE Grant we set up a more rigorous and randomized experimental design, which included a checkerboard-mulching scheme with three treatments; kempy wool, hay, and a control treatment with no mulch. In addition to looking at eggplants, we also evaluated peppers and tomatoes. Four replicates of each treatment were included in the experimental area (each plot measured roughly 4ft x 4ft). A portable weather station was also employed at the plots to measure environmental variables. In addition to confirming our results from 2010 our aim was to gain an understanding of the other beneficial contributions of wool, particularly its mode of action by assessing such environmental factors as soil moisture, air temperature, and precipitation. Although our subjective research already suggested that wool is an excellent weed deterrent, we were curious about the other impacts of the wool that resulted in the improvements in plant vitality and production. We compared wool mulch, hay mulch (pseudo control), and no mulch (control) using a randomized planting scheme with four replicates (plants) per treatment group and a total of as many as 100 single variety of tomatoes, eggplant, and peppers. The use of monitoring equipment, namely the HOBO weather station allowed us to repeat our preliminary experiments while monitoring critical environmental variables. Sampling occurred three times each week over the course of the 4-month experiment. Rain events provided water to the plants and in the event of a drought (as our soil has high organic matter content), watering occurred once a week on a standard treatment for each row.

Mulching with Wool
Eggplant with hay mulch.

Our results were confirmed in 2011 that again the wool mulch played an enormous role in increasing productivity and yield. Foliar analysis was conducted and the results showed an increase in nitrogen in samples mulched with wool. We also found that temperatures under the wool were less variable. In addition, moisture levels were more constant under the wool. We had an excess of wool after the experiment was established, and we used the wool mulch on sweet potatoes and found again the dark leaf coloration, but also that deer damage was mitigated. Three rows of sweet potatoes mulched with hay next to the wool mulched rows were obliterated by deer damage, however, the rows mulched with wool were untouched. Out of the rows mulched with wool we harvested almost 4 times more sweet potatoes, than the un-mulched/deer damaged rows. Not only did nitrogen availability to the plants (eggplants) increase, but, due to this increase in nitrogen we concluded that we could save considerably on the cost of fertilizer and labor due to reduction in time spent on cultivation. We also would no longer have to consider taking up valuable space in our hay-lofts to store this wool, thereby saving in overhead costs. We believe that many organic farmers will have the potential to benefit by mulching with wool especially if they can network with wool-growers in their area.

Mulching with Wool
Eggplant with wool mulch.