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How Interested are Crop Farmers in Using a Fertilizer Derived from Dairy Manure?

Posted by Karen Hills | December 9, 2020
It used to be that livestock and crops were integrated on a single farm and manure provided an important source of fertility for crop production. However, the advent of commercial fertilizer, increased specialization on farms and more concentrated livestock operations meant that manure is often viewed as a liability rather than as a resource. Dairy farms are a good example of farms that often have a surplus of nutrients.  And yet, if these nutrients could be recirculated to crop farms, they could provide valuable nutrients for crop growth.

Cows eat at an indoor feed rail
Manure from dairy cows already provides valuable nutrients for growing feed on dairy farms. In some cases, exporting those nutrients for use on crop farms provides a benefit to the dairy in terms of achieving nutrient management goals as well as improving the overall sustainability of agricultural systems. Photo: USDA, under CC BY-NC-ND 2.0

One particular approach to nutrient recovery, called Dissolved Air Flotation (DAF), concentrates the nutrients, providing more options for transport to distant farm fields or export off-farm (Benedict et al. 2018). I described results of a food safety of fertilizers derived from dairy manure, including DAF solids, when applied to raspberries in a previous post.

Two years ago, I had the opportunity to participate in a project surveying crop farmers for a project looking at whether demand existed for manure-derived fertilizer. Understanding crop farmers’ perspective is important, because being able to produce a safe and effective product is not of any use without a viable market. To this end, I worked with a team at the Center for Sustaining Agriculture and Natural Resources and Dr. Joe Cook from Washington State University’s School of Economic Sciences to better understand how crop farmers would view this product, particularly focusing on willingness to pay and attributes of potential importance to end users.

We distributed a survey to crop growers and crop consultants at three grower meetings in Washington State in late 2018. We used what is called a “discrete choice experiment” in which participants are asked to make hypothetical choices between options combining three attributes that we were interested in: distribution channel, form, and price. One option was always to stay with the “status quo” fertilizer. For the sake of this exercise, we asked respondents to assume no food safety issues, no additional regulatory burden, and assume that the product could be used in certified organic production (it currently can’t be due to a polymer used in the process). Of the 90 surveys that were distributed, 37 were returned, representing 27 growers and 10 crop consultants in a variety of crop types, representing both conventional and organic production systems. Then came the fun part – number crunching.

We found that distribution channel – in other words, whether or not the manure-derived fertilizer was obtained through a grower’s existing fertilizer supplier – had no impact on whether a respondent was more likely to choose the manure-based fertilizer over their status quo fertilizer regime.

The product resulting from the dissolved air flotation process is in a semi-wet form (like wet compost) but we anticipated that an air dried or pelletized it may help with ease of storage and transport, or spreading. As we suspected, respondents did prefer air dried or pelletized to wet forms of the product. The inclusion of a price attribute helped us understand how much more respondents were willing to pay for the various forms of the product. We assumed that the price would need to be the same or less than current fertilizer prices to be desirable, so set the price at 50%, 75%, or the same as current fertilizer prices. Our results indicate that respondents were willing to pay 23% and 39% more for air dried and pelletized products, respectively, than for the semi-wet option.

Texture of manure in semi-wet, air dried and pelletized forms, and appropriate delivery devices..
Form of dairy-manure derived solids may be important for market uptake, with a greater willingness to pay for air dried or pelletized DAF solids.

Our results also indicated that there are other factors beyond the ones we asked about that led respondents to stay with their current fertilizer regime in the hypothetical choice exercise. Responses to open-ended questions provided some clues about those factors. For example, understandably, growers wanted much more information, particularly field trial results and information on nitrogen release. Matching the timing of nitrogen release with crop needs is critical, but can be challenging to achieve with organic fertility sources such as this manure-derived product. There may be an opportunity to focus on the soil building properties of the biofertilizer, as some respondents expressed an interest in building organic matter and micronutrients in soil through use of this product, rather than using it primarily as a source of macronutrient (nitrogen, phosphorus, potassium) fertility.

Manure applied along base of established raspberry canes.
Phosphorus rich solids from Dissolved Air Flotation (DAF) were applied to established raspberry plantings for a research trial in Whatcom County, Washington. Photo: Chris Benedict.

The reality of the situation is that nutrient recovery technologies, such as the one used to produce the manure-derived fertilizer considered by survey respondents, are expensive and cash-strapped dairies are likely to have a difficult time investing in such equipment, at least in the near term. Adoption will require progress on several fronts, including both development of markets for resulting products (the focus of this study) and a broader recognition of the value that such systems provide in terms of helping dairies achieve their nutrient management goals and providing recycled nutrients to croplands, substituting at least partially for synthetic fertilizers and, thus, improving overall watershed nutrient balances.

For more details on the survey project, see the published paper.

For more information on the larger “Dairies to Berries” project, funded through a Conservation Innovation Grant from the Natural Resources Conservation Service, see the project website.

References