Wyoming is famous for its harsh climate, and any local knows it’s something Wyomingites embrace with pride. Throughout our state’s history, the struggle with nature has created a special need for resiliency—a resiliency that might well describe many of Wyoming’s agricultural systems. It’s no wonder that ruminant animals, namely cattle and sheep, traditionally have been the cornerstone of Wyoming agriculture, with their ability to eke out a living on Wyoming’s vast grazing resources making them the ideal food producers on our state’s non-arable lands.

Early settlers quickly discovered, however, that maintaining animals through Wyoming winters requires stored forage and a lot of it—as much as 2–2.5 tons of hay per cow each year. For many ranchers today, this critical winter forage is produced on mountain hay meadows, areas of the landscape near rivers and streams where large swaths of grass hay are flood-irrigated with water from spring runoff. Meadows traditionally have been a low-input forage system that utilizes simple ditches and canals to expand the footprint of irrigable land near a water source. With the introduction of water, meadows developed naturally as water-loving sedges, rushes and grasses replaced hardy prairie vegetation, and after nearly a century, the continued influence of flood irrigation has shaped meadows as we know them today.

Although irrigating meadows increased the productive capacity of ranches, inefficient irrigation creates some unique management challenges. Meadows routinely remain saturated for weeks to months in the spring and early summer as forage grows prior to harvest. The excess water makes fertility management difficult, because fertilizers are subject to runoff, leaching and gaseous losses from the field. Early research found that, at best, the nitrogen-use efficiency of meadows caps out around 30%, and that meadows routinely respond to nitrogen fertilizer inputs. Low productivity means ranchers must balance management decisions to ensure they have enough hay available for the winter.

With recurring drought causing hay prices to skyrocket in recent months, and economic struggles of the pandemic causing fertilizer prices to double in just one year, it is time to reassess meadow management and sustainability. Here we share new ongoing research in the Departments of Ecosystem Science and Management and Plant Sciences that seeks to better understand meadow hay production for a new generation.

Meadow soils are unique

Early research on meadows focused on agronomic and economic management strategies to maximize forage production and value for livestock producers in the Mountain West. Studies of fertilizer response, grazing, harvest, and irrigation in the 1960s and 1970s provided the foundational meadow management tactics that still are in use today. An overriding theme in the early literature is that meadows are difficult to manage because of their unique soils, as influenced by flood irrigation. Researchers commonly described the surface horizon of meadow soils as being high in organic matter and stored nutrients that were of limited availablity to plants. This “thatch” or “sod-bound” layer developed because of the reduced decomposition of organic matter in the soil during saturated conditions, which in turn did not recycle nutrients for plant growth in subsequent years. Although researchers found as much as 1–2 tons per acre of organic nitrogen in the thatch layer, they acknowledged its unavailability as a disconnect in the nutrient cycling of meadow soils.

As Wyoming steps into a future of increasing demand for food production, it is critical to utilize every resource available for plant growth. Thus, our research began as an initial curiosity about the large amounts of stored nitrogen in meadow soils. We quickly realized the thatch layer, or specifically, the O-horizon (“O” signifying a high concentration of organic matter) needs to be examined more closely. We hypothesized that continuous flood irrigation has led to the development of an O-horizon that is limiting nitrogen availability for hay production, and that proper management can naturally release nitrogen from the system for increased plant growth.

After one year of data collection, we are finding evidence to support our hypothesis. In spring of 2021, we identified four local ranches that utilize flood irrigation for meadow hay production. At each ranch, we are comparing three unique agroecosystems: long-term fertilized, irrigated hay meadows; long-term unfertilized, irrigated hay meadows; and corresponding natural rangelands. By excavating the soil in all three agroecosystems, we confirmed that continuous flood irrigation leads to the development of an O-horizon in meadow soils.