Digital mapping of structural conservation practices in the Midwest U.S. croplands: Implementation and preliminary...

The application of best management practices is a long-term conservation effort in Midwest U.S. croplands, and many farmers have adopted structural conservation practices (SCPs) to reduce soil erosion and surface water runoff, such as terraces and grassed waterways. Despite that, the geographic distribution of these practices is barely known in the region, and mapping initiatives are required to develop timely and spatially explicit inventories of SCP areas. This study presents the first mapping of SCPs in the agricultural areas over 12 Midwest U.S. states. Semantic segmentation model (adapted U-Net) and National Agriculture Imagery Program 2018-2019 data were used to map the SCP areas at 2-m spatial resolution (490.2 billion pixels). In general, mapping results achieved 78.2% overall accuracy across 20 counties. Our results indicate that 52% of SCP areas are distributed over Iowa (26%), Illinois (15%), and Nebraska (11%). In contrast, the states with the lowest SCP areas are Michigan and North Dakota, with less than 4% of SCP areas. Since the SCP extent is also dependent on the number of cropland areas per state, the percentage of SCP per cropland area was calculated. Specifically, the average percentage of SCP area per cropland is ~1.19%, ranging from 0.8 (e.g., North Dakota and south Minnesota) to 5.5% (e.g., northeast Kansas and southwest Iowa). Interestingly, results also illustrate that regions with high soil erosion rates present the largest percentage of SCP areas in croplands, indicating conservation efforts by farmers. While this preliminary analysis shows some limitations in the mapping quality (mislabel, non-accurate location or discontinuity of SCP areas), the framework has a potential for operational conservation monitoring. The development of such mapping has positive implications for conservation programs, and this geospatial inventory is easily accessible information for the large-area evaluation of conservation practices across Midwest U.S. croplands.