# Regional Crop Gross Primary Productivity and Yield Estimation Using Fused Landsat-MODIS Data
## 3 Results
### Crop Yield Monitoring in Montana
For these crops, the most accurate model predictions are concentrated in the north-central part of the state, termed the 'Golden Triangle' and known for highly productive dryland grain farming; model accuracy is generally lower moving in any cardinal direction from this region. The spatial patterns of model uncertainty for barley production (Figure 7c) is moderate, with generally better model performance in the north-central portions of MT around Pondera, Teton, Choteau and Glacier counties. However, the model results exhibit somewhat larger uncertainties in the eastern part of the state, where counties are less specialized in barley production and farming practices are more variable. The eight-year study period was too short for effectively quantifying and diagnosing regional trends in planted area and crop yield/production. However, the total planted area for all seven MT crop types showed a significant increasing trend from 2008 (4.36 \(\times\) 10\({}^{6}\) hectares) to 2015 (5.95 \(\times\) 10\({}^{6}\) hectares). The statewide averaged crop production for alfalfa was 3.01 \(\times\) 10\({}^{6}\) ton during the study period, with two annual production peaks in 2010 (3.83 \(\times\) 10\({}^{6}\) tons) and 2013 (3.21 \(\times\) 10\({}^{6}\) tons) (Figure 8). The amount of land allocated to alfalfa increased during the study period at a rate of 1.52 \(\times\) 10\({}^{5}\) hectares per year. Alfafla is relatively productive (3.77 \(\pm\) 1.06 tons/hectare) and has a larger planted area (3.63 to 18.05 \(\times\) 10\({}^{5}\) hectares) in MT during 2008 to 2015 than the other six crop types. Barley showed a strong increasing trend in crop production from 2011 to 2015, together with a significant increase in planted area (Figure 8). Maize showed an increasing trend in planted area from 2008 to 2014, but did not show a congruent increase in crop production; maize production also peaked in 2013 (2.00 \(\times\) 10\({}^{5}\) ton) relative to the other years examined (Figure 8). Though maize represented the lowest planted area of the major MT crops from 2008 to 2015, peas showed significant and consistent increasing trends in crop  
Figure 7: Standard error of model estimated annual crop production compared with USDA NASS reported crop production records per county for (**a**) alfalfa, (**b**) spring wheat, (**c**) barley and (**d**) winter wheat across MT. The NA term and associated white areas denote MT counties with no reported NASS crop production data for the crop types examined in this study. production and planted area during the study period (Figure 8). However, the crop yield for peas was 1.24 \(\pm\) 0.28 tons/hectare, covering approximately 3.7% of the total cropland area in MT. There were no obvious trends in planted area or production for MT wheat crops (Figure 8). Spring wheat and winter wheat were planted over large areas in MT (>1.10 \(\times\) 10\({}^{6}\) hectare), while estimated annual production and yield for these two cereal crops averaged 1.27 \(\pm\) 0.27 and 1.90 \(\pm\) 0.39 ton/hectare during the study period, respectively.