Soybean [Glycine max (L.) Merr.] yield formation in fi eld environments can be either source-limited or sink-limited, depending on the assimilatory capacity of the mother plant relative to the assimilate demands of the developing seeds. Our objective was to evaluate yield and seed quality relationships under source-limited and sink-limited conditions during the seed-fi lling period, as protein and oil comprise on average more than 600 g kg -1 of the soybean seed. Field experiments were conducted in fi ve central Minnesota environments to examine the eff ects of multiple pod removal, shade, and defoliation treatments on soybean yield, seed size, seed protein concentration, and seed oil concentration. Pod removal, shade, and defoliation treatments each resulted in decreased yield and altered protein and oil concentrations relative to the control. Averaged across all levels for each treatment, pod removal increased seed size 19% over the control, while defoliation and shade resulted in respective seed size reductions of 7.7 and 15% when compared to the control. Despite diff erential treatment eff ects on individual seed growth, pod removal and shade treatments each resulted in increased seed protein concentration and decreased seed oil concentration. In contrast, defoliation resulted in seeds with lower protein concentration and higher oil concentration than pod removal and shade. Pod removal and shade eff ects on seed quality diff ered primarily in magnitude, as the average oil concentration across all shade treatments was 10 g kg -1 lower than the average oil concentration across all pod removal treatments. No individual treatment resulted in increased oil concentration relative to the control.

The terrestrial water budgets of the Prairie Coteau (PC; 38,000 km2) and Northern Glaciated Plains (NGP; 66,000 km2) regions of South Dakota, USA were characterized using a combination of in situ observations of groundwater and surface water, remote sensing estimates of terrestrial water storage changes from the Gravity Recovery and Climate Experiment (GRACE) and surface water changes from Landsat, and modeled changes in soil moisture, snow water equivalent, and total canopy water storage. In response to increased wetness in 2010 and 2011 over the region, prevalent surface water bodies accounted for a significant fraction of the terrestrial water budget of the PC, whereas the NGP, an area with sparse surface water, exhibited a greater increase in groundwater storage concomitant with enhanced seasonal variability. Over the study period from 2003 to 2011, GRACE‐based estimates of terrestrial water storage agreed well with combined groundwater, soil moisture, snow water equivalent, and total canopy water storage over the NGP, as surface water is not a significant component in this area. However, closure was improved over the PC if surface water changes were included in the water budget.

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This investigation used a modified parameterization of the Agricultural Land Management Alternative with Numerical Assessment Criteria (ALMANAC) model to improve simulated growth and biomass yield of upland switchgrass (Panicum virgatum L.) ecotypes in northern U.S. locations. Leaf area development, biomass accumulation, and N utilization of upland ecotypes were parameterized by field evaluations from Montreal, QC, Canada, and sites throughout the northern U.S. Great Plains. Resulting ALMANAC simulations were validated against measured yields from 66 location–years of switchgrass production across 13 sites in Minnesota, North Dakota, and South Dakota. As contrasted to the model defaults, the modified parameterization reduced RMSE of annual simulated yields from 3.77 to 2.62 Mg ha−1 and improved percentage bias from −16 to 13%. Model performance was most improved in environments with no N fertilization, where ALMANAC simulated annual yields with an RMSE of 1.73 Mg ha−1 and percentage bias of −0.5%. Relative to the default ALMANAC parameterization, the modified parameterization also simulated a longer growing season and extended the median simulated maturity date from 1 to 28 August, greatly improving the estimation of switchgrass phenology within the study region. Sensitivity analyses revealed that simulated switchgrass yield was unaffected by modifications of runoff curve number and was most affected by modifications of radiation use efficiency. The other seven parameter modifications each had a median yield impact of 0.57–1.4 Mg ha−1. This work provides an improved characterization of upland switchgrass ecotypes in northern U.S. locations for future ALMANAC users.

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