Source: Potato Grower
Before continuing this article, readers should ponder their response to the question posed in the subtitle: What do you think about manure usage in cropping systems? Would you use manure as a fertilizer to grow potatoes, small grains and/or other crops? Is it superior or inferior to inorganic fertilizers? How would manure usage in cropping systems impact soil health metrics and crop production?
According to the UN’s Food and Agriculture Organization (FAO), manure is underutilized worldwide, with less than 25 percent of manure generated applied as fertilizer. For livestock operations, nutrients in the form of feed are imported onto the farm. Meanwhile, crop-producing operations import nutrients in the form of inorganic fertilizers. The application of inorganic fertilizers to regional cropland instead of manure utilization represents a net increase of nutrients to the region. This contributes to a regional imbalance and over-application of nutrients. Connecting livestock producers who have an excess of livestock manure with crop farmers who can utilize manure as a fertilizer and offset application of inorganic fertilizer can provide a win-win situation. Furthermore, manure and compost application can improve soil health by increasing soil carbon because those products are high in organic carbon themselves.
Soil health can be defined as the continued capacity of soil to function as a vital living system, within ecosystem and land-use boundaries, to sustain biological productivity, promote the quality of air and water environments, and maintain plant, animal and human health. For cropland, this definition can be interpreted as the continued capacity of soil to function as a vital living system to sustain healthy crop production. The bottom line is that if soil is not healthy, crop production becomes increasingly more difficult and expensive. For example, if soil microbial populations are diminished (through tillage, fumigation, etc.), fewer nutrients are cycled. This means more inorganic fertilizer should be applied and there is a higher risk for nutrient loss to the environment.
In southern Idaho, one barrier to this win-win situation is potentially negative perceptions of dairy manure and compost applied as fertilizer by crop producers. Thus, a survey was developed in 2020 to assess agricultural producers’ and their advisors’ perceptions of the benefits and challenges of manure use in cropping systems.
Overall, manure application was perceived to be beneficial for crop fertility and crop yields, as well as to soil health metrics such as soil biology, soil water-holding capacity and nutrient cycling. Seventy-one percent of the 128 respondents indicated that manure and inorganic fertilizer were complementary nutrient sources in cropping systems; 11 percent indicated they were independent of each other; 11 percent indicated they felt the two were competing, with inorganic fertilizer being preferred; and 7 percent indicated they were competing products with manure being preferred.
Respondents were asked what challenges they observe to using manure in cropping systems in regard to several factors: economic, agronomic, neighborhood or rural community, logistics, and regulatory. Responses were separated and ranked according to whether the respondent was an agricultural producer or an advisor. Both agricultural producers and advisors perceived the cost of manure transportation and land application to be the top challenge. Weed seed introduction was viewed as the greatest agronomic challenge by both groups, but other top challenges varied. Specifically, for producers, the categories that manure presented the most challenges to were logistics and agronomic, while their advisors indicated that agronomic challenges were the biggest hurdles.
These survey results are important for several reasons. First, agricultural producers and their advisors identify that manure can benefit soil health metrics such as soil biology, water-holding capacity and nutrient cycling. However, there is a disconnect between producers and their advisors about the barriers to manure usage. Advisors perceive manure as being a challenge in many agronomic ways, such as unpredictability of crop-available nutrients and poor uniformity of manure application. This may lead to manure being under-recommended as a fertilizer.
Understanding these perceptions will be valuable in developing educational programming and research topics that will help agricultural producers successfully recycle manure nutrients. Consider this question again: What do you think about manure usage in cropping systems?
Author Linda Schott is an assistant professor and extension specialist in nutrient and waste management based at the University of Idaho’s Twin Falls Research & Extension Center. She can be contacted at lschott@uidaho.edu.