# Mixed-Species Cover Crop Biomass Estimation Using Planet Imagery
## 2 Materials and Methods  
### Site and Experiment Description  
The study was conducted at the USDA, Agricultural Research Service (ARS), Crop Production Systems Research Unit (CPSRU) research farm located in Stoneville, MS, in the mid-south region of the USA (33\({}^{\circ}\)26\({}^{\prime}\)36.24\({}^{\prime\prime}\) N and 90\({}^{\circ}\)53\({}^{\prime}\)3.08\({}^{\prime\prime}\) W). Four separate ongoing research study sites (Figure 1) with different cover crop species and seeding rates were selected for this study within the CPSRU research farm. The soil texture within these study sites was predominantly Commerce series (fine-silty, mixed, superactive, nonacid, thermoc Fluvaquentic Endoaqueous), with some Dowling series (very-fine, smecititic, nonacid, thermoc Vertic Endoaqueous). Figure 1: Study site and data products used. (**A**) Mississippi state map with the Crop Production Systems Research Unit (CPSRU) location marked as star; (**B**) four study sites with cover crops (labeled 1–4) within CPSRU research farm (red with main crop corn and yellow with soybean, cover crop treatment detail is provided in Table 1); (**C**) hyperspectral spectroradiometer (Fieldspec4 Standard-Res) used to collect 350-2500 nm canopy reflectance; and (**D**) Planet imagery downloaded for the study site through Planet Explorer. Each of the four study sites was established with a randomized complete block design (RCBD) with four replications to evaluate cover crop and other treatments on main crop productivity and soil health. Plots within all four study sites that included cover crop treatments were selected for this paper. Hence, study sites 1, 2, 3, and 4 contained a total of 12, 16, 16, and 32 plots, respectively, with cover crop and fallow treatments (Table 1). Biomass from fallow plots of study sites 2 and 3 were not collected, thus a total of 68 plots (12, 12, 12, and 32 plots for study sites 1, 2, 3, and 4, respectively) were used to perform the analysis for this paper. Study sites 1 and 4 (Figure 1) contained eight rows for each plot (32 m \(\times\) 8.4 m), while study sites 2 and 3 consisted of four rows per plot (12 m \(\times\) 4.2 m). All four study sites were planted with cover crop treatments between the last week of October and the first week of November in 2020 and 2021 (Table 1). Study site 1 comprised three cover crop treatments: rye (_Secale cereale_ L.), rye + crimson clover (CC, _Trifolium incarnatum_ L.), and no winter cover crop, planted both in no-till and conventional till plots. Data from both no-till and conventional till plots were combined in study site 1. The main crop at study site 1 was soybean (_Glycine max_ L.), planted a week after cover crop termination. Study sites 2 and 3 contained mixed-species cover crops seeded with different seeding rates (Table 1). Species included were Austrian winter pea (_Pisum sativum_ L.), rye, crimson clover, hairy vetch (_Vicia villosa_ Roth), wheat (_Triticum aestivum_ L.), oats (_Avena sativa_ L.), and purple turnip (_Brassica rapa_ L.). The main crop at study sites 2 and 3 were soybean and corn (_Zea mays_ L.), respectively. Study site 4 included rye, hairy vetch, and crimson clover as individual species and a mix of these cover crop species (Table 1). The main crop at study site 4 was corn. Standard recommended agronomic practices for the main crop (corn and soybean) were followed with fertilizer and herbicide application while cover crop received no fertilizers and herbicides. Cover crops were terminated a week before main crop planting by application of paraquat dichloride. Weather data were downloaded from Delta Agricultural Weather Center, Stoneville, MS (2.5 km from study plots) ([[http://deltaweather.extension.msstate.edu/stoneville-aws](http://deltaweather.extension.msstate.edu/stoneville-aws)]([http://deltaweather.extension.msstate.edu/stoneville-aws](http://deltaweather.extension.msstate.edu/stoneville-aws)), accessed on 20 November 2022).