Wisconsin has been proudly known as America’s Dairyland for many years. However, recent data on dairy farms in the Driftless Region (Figure 1)
are suggesting times are changing in the dairy industry for Western Wisconsin and surrounding states. According to the USDA NASS, the number of dairy farms in the Driftless Region with less than 100 head of cattle have been on the decline over the past 10-15 years. On the flip side, farms with 100+ head of cattle have been increasing [1]. The largest dairy farms (>500 head) more than doubled their number between 2007 and 2017. In total, the number of dairy farms showed a slight (<10%) decrease over the same period (Figure 2). This is, in essence, a “consolidation” of dairy farms, where although the total number of dairy farms has not changed drastically, there is a pronounced shift from small dairies to large dairies occurring in this region.
The consolidation of dairy farms in the Driftless Region has been accompanied by substantial changes in the area of annual row crops planted in the region. Over 14 HUC-8 levels watersheds in the Driftless Region (all of which drain into a Mississippi River tributary), a spatial analysis of USDA Cropland Data Layer data indicates that annual crop (corn, soybeans, and wheat) acreage increased in every watershed between 2006 and 2017 (Figure 3a). Across the 
watersheds, row crop acreage increased by 20,000 or more acres, which for some watersheds was a >30% increase from 2006 acreage (Figure 3b). Most of the land that was converted to row crops came from grasslands & pastures (51.6%) or alfalfa (23.2%) (Figure 4). This reflects the dairy farm consolidation trends in that as the small dairies go out of business, less land is needed for pasture or alfalfa and may be converted to row crops. Another reason for the large increase in row crop acreage could be a strong biofuel market in the late 2000s, which increased the incentive to put more land into production [2,3].
So what are the environmental impacts of such changes? Research is currently underway to quantify the relationships between the trends in row crop acreage, annual precipitation, and regional hydrology that have been observed in the Driftless Region watersheds. We expect this work to be published in the near future. However, similar studies have shown the ways in which row cropping can influence the landscape and impact hydrologic processes. The steep topography of the Driftless Region makes any land that is utilized for row crops particularly vulnerable to soil erosion and compaction [4]. This impacts the hydrologic cycle by reducing the ability of water to infiltrate into the soil profile, which in turn increases runoff [5,6]. With a shift from perennial vegetation to annual row crops (which has been the case with the Driftless Region over the past 10-15 years), there are now periods where the ground is fallow before planting/emergence and after harvest and is highly susceptible to erosion/runoff [5,6,7]. Along with the land cover changes, increases in annual precipitation were observed in the Driftless Region between 2006 and 2017 (Figure 5), which can act to enhance these effects [8,9]. Overall, these findings suggest that the result of an increase in row crop acreage and annual precipitation is an increase in the amount of water leaving the landscape into the waterways. Not only does this affect local hydrology, but in the case of the Driftless Region, it is likely to result in an increase in water, sediment, and nutrients leaving the region via the Mississippi River down to the Gulf of Mexico. Therefore, any future row crop expansion should be accompanied by careful management decisions motivated by both economic and environmental factors.
Collaborators: Andy VanLoocke, ISU Department of Agronomy; Shane Hubbard, UW-Madison Space Science & Engineering Center; Chris Kucharik, UW-Madison Department of Agronomy
Thanks to the ISU Department of Agronomy & the UW-Madison Space Science & Engineering Center for supporting this research!
Sources
[1] USDA National Agricultural Statistics Service (NASS). Website: https://www.nass.usda.gov/.
[2] Lark, TJ, Salmon, JM, & Gibbs, HK (2015) ‘Cropland expansion outpaces agricultural and biofuels policies in the United States’, Environmental Research Letters, 10.
[3] Schilling, KE et al. (2008) ‘Impact of land use and land cover change on the water balance of a large agricultural watershed: Historical effects and future directions’, Water Resources Research, 44(7), pp. 1–12.
[4] Potter, KW (1991) ‘Hydrological impacts of changing land management practices in a moderate-sized agricultural catchment’, Water Resources Research, 27(5), pp. 845–855.
[5] Juckem, PF, et al. (2008) ‘Effects of climate and land management change on streamflow in the driftless area of Wisconsin’, Journal of Hydrology, 355(1–4), pp. 123–130.
[6] Knox, JC (2001) ‘Agricultural influence on landscape sensitivity in the Upper Mississippi River Valley’, Catena, 42(2–4), pp. 193–224.
[7] Zhang, YK and Schilling, KE (2006) ‘Increasing streamflow and baseflow in Mississippi River since the 1940 s: Effect of land use change’, Journal of Hydrology, 324(1–4), pp. 412–422.
[8] Rogger, M, et al. (2016) ‘Land use change impacts on floods at the catchment scale: Challenges and opportunities for future research’, Water Resources Research, 53, pp. 5209–5219.
[9] PRISM Climate Group, Oregon State University (2017) 'PRISM Climate Data' [online]. Website: http://prism.oregonstate.edu.