# Mixed-Species Cover Crop Biomass Estimation Using Planet Imagery
## 3 Results
### Planet Imagery and Cover Crop Biomass--ANOVA  
The four study sites had different cover crop species and mixed combination treatments. Their biomass production ranged from 2.48 Mg ha\({}^{-1}\) for study site 1, fallow plot,  
Figure 3: Cover crop seeding rate and pure live seed effect on biomass (across all four studies and cover crop species/mix for both year 2021 and 2022): (**A**) biomass yield and seeding rate linear relationship; (**B**) biomass return per kilogram of seeds; (**C**) biomass and pure live seeds linear relationship; and (**D**) biomass return per square meter of pure live seeds. Least square mean (individual points on the figure) of each treatment was used to plot the relationship and trends. \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline
**Bands and VIs** & **Nov** & **March** & **April\_A** & **April\_B** & **Nov** & **March** & **April\_A** & **April\_B** \\ \hline \multicolumn{1}{c}{} & \multicolumn{3}{c}{Correlation with biomass} & \multicolumn{3}{c}{Correlation with seeding rate} \\ \cline{2-9}  & \(-\)0.01 & \(-\)0.34 & \(-\)0.54 * & \(-\)0.54 * & \(-\)0.03 & \(-\)0.35 & \(-\)0.48 & \(-\)0.47 \\ Green & \(-\)0.15 & \(-\)0.24 & \(-\)0.54 * & \(-\)0.54 * & \(-\)0.11 & \(-\)0.26 & \(-\)0.48 & \(-\)0.48 \\ Red & 0.02 & \(-\)0.42 & \(-\)0.53 * & \(-\)0.42 & \(-\)0.02 & \(-\)0.42 & \(-\)0.46 & \(-\)0.40 \\ NIR & 0.41 & 0.74 * & 0.55 * & 0.39 & 0.26 & 0.57 * & 0.39 & 0.24 \\ NDVI & 0.21 & 0.56 * & 0.57 * & 0.43 & 0.13 & 0.52 * & 0.46 & 0.34 \\ EVI & 0.32 & 0.66 * & 0.57 * & 0.44 & 0.21 & 0.57 * & 0.42 & 0.35 \\ EVI2 & 0.41 & 0.62 * & 0.57 * & 0.43 & 0.25 & 0.52 * & 0.43 & 0.33 \\ MSR & \(-\)0.13 & 0.00 & 0.27 & 0.50 * & \(-\)0.05 & 0.24 & 0.33 & 0.43 \\ OSAVI & 0.35 & 0.61 * & 0.57 * & 0.42 & 0.23 & 0.54 * & 0.44 & 0.31 \\ SR & 0.20 & 0.60 * & 0.56 * & 0.45 & 0.13 & 0.56 * & 0.45 & 0.34 \\ ExG & \(-\)0.35 & 0.33 & 0.25 & 0.03 & \(-\)0.23 & 0.21 & 0.16 & 0.03 \\ ExR & 0.08 & \(-\)0.44 & \(-\)0.47 & \(-\)0.31 & 0.06 & \(-\)0.48 & \(-\)0.45 & \(-\)0.31 \\ \hline \hline \end{tabular} Note: refer to Table 2 for VI derivation information. * Statistically significant at \(p\leq 0.05\).  
\end{table} 
Table 3: Pearson correlation coefficients of PlanetScope bands and vegetation indices (VI) during November (Nov), March, and April (April_A = 1-15 April; April_B = 15-30 April) with cover crop biomass and seeding rate. to 6.65 Mg ha\({}^{-1}\) for study site 4, rye + clover + vetch cover crop combination (Table 4). Only two study sites (1 and 4) included biomass measurements from follow plots, where weeds with random mixture of swinecress (_Coronopus didynus_ (L-) _Sm._), hairy buttercup (_Rannunculus sardous_ Crantz), henbit (_Lanium amplexiaule_ L), white clover (_Trifolium repens_ L), and Italian ryegrass (_Lolium perenne_ L. ssp. _multiforum (Lam.) [PERSON]_) were observed. Weeds were completely suppressed in the cover crop plots. Overall, higher biomass was observed at study sites 1 (5.17 Mg ha\({}^{-1}\)) and 4 (5.31 Mg ha\({}^{-1}\)) compared to study sites 2 (3.20 Mg ha\({}^{-1}\)) and 3 (3.30 Mg ha\({}^{-1}\)), where fallow plots were excluded. At study site 1, the rye cover crop produced 80% more biomass than the fallow plot. Rye + clover mix produced 32% more biomass compared to the rye cover crop. Even though biomass differed by CC treatment, none of the reflectance bands and indices were affected by these biomass differences. At study site 2, neither cover crop biomass nor any reflectance bands and indices were affected by cover crop treatment. At study site 3, the low seeding rate (50 kg ha\({}^{-1}\)) of legume mix and cereal mix produced 3.1 and 3.3 Mg ha\({}^{-1}\) biomass, respectively; however, they were not statistically significantly different. The high seeding rate (135 kg ha\({}^{-1}\)) of legume + cereal mix (HiMix-LC treatment) produced 3.5 Mg ha\({}^{-1}\) biomass, and it was statistically significantly different from low seeding rate legume mix only. The canopy reflectance index EVI showed the highest value with legume mixed and the lowest with legume/cereal mix.