winter rye (Secale cereale l.) cover crop (rcc) has potential to reduce no 3 -n loss from corn (Zea mays l.) and soybean [Glycine max (l.) Merr.] fields. However, rcc effects on annual crop productivity and corn optimal n fertilization requirement are unclear. the objectives were to evaluate corn and soybean yield response to rcc and corn optimal n rate. treatments were no-rcc and rcc with six fertilizer n rates (0-225 kg n ha -1 ) applied to corn in a no-till corn-soybean (cs) rotation at four iowa sites in 2009 through 2011. the rcc biomass and n uptake was low, with a maximum of 1280 kg dry matter (dM) ha -1 and 26 kg n ha -1 , respectively. in the no-n control, the rcc reduced soil profile no 3 -n by 15 kg n ha -1 only at time of rcc control before corn planting. corn canopy sensing, plant height, and plant population indicated more n stress, reduced plant stand, and slower growth with rcc. the rcc reduced corn grain yield by 6% at the economic optimum n rate (eonr). the eonr was the same with no-rcc and rcc, but plant n uptake efficiency (Pue) was reduced at low n rates with rcc, but not above the eonr. soybean yield was not affected by rcc. results indicate n fertilization rate should be the same with or without rcc. improvement in rcc systems and management could make rcc a more viable practice within notill corn and soybean production.Abbreviations: CS, corn-soybean; DM, dry matter; EONR, economic optimum nitrogen rate; NDVI, normalized difference vegetative index; NUE, nitrogen use efficiency; PAN, plant available nitrogen; PUE, plant nitrogen uptake efficiency; RCC, rye cover crop; SOM, soil organic matter; YEONR, yield at economic optimum nitrogen rate. E nvironmental concerns related to crop N fertilization is an ongoing issue (USEPA, 2007), including reducing N in surface waters related to hypoxia in coastal surface waters Kladivko et al., 2014). Nitrogen application rate to corn is an important factor in regard to cropping system profitability and NO 3 loss. Applying only the optimal N rate will not stop NO 3 loss, nor necessarily achieve the drinking water standard (Lawlor et al., 2007). Successful development of agricultural systems that benefit water quality have to be more inclusive of several agricultural practices, rather than only N rate or timing (Hatfield et al., 2009). Therefore, additional in-field practices are needed to reduce NO 3 losses (Sainju and Singh, 2008).Nitrate losses in tile drainage water from corn production systems can range from 7 to 68 kg N ha -1 yr -1 (Lawlor et al., 2007), and with most values ranging from 29 to 56 kg N ha -1 yr -1 (Sawyer and Randall, 2008). Cover crops have shown potential for uptake of residual N from fertilizers or inorganic N released from degrading soil organic matter (SOM) in the period between annual crops (Strock et al., 2004;Tonitto et al.,

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a b s t r a c tThe ability of biogeochemical ecosystem models to represent agro-ecosystems depends on their correct integration with field observations. We report simultaneous calibration of 67 DayCent model parameters using multiple observation types through inverse modeling using the PEST parameter estimation software. Parameter estimation reduced the total sum of weighted squared residuals by 56% and improved model fit to crop productivity, soil carbon, volumetric soil water content, soil temperature, N 2 O, and soil NO 3 À compared to the default simulation. Inverse modeling substantially reduced predictive model error relative to the default model for all model predictions, except for soil NO 3 À and NH 4 þ . Post-processing analyses provided insights into parametereobservation relationships based on parameter correlations, sensitivity and identifiability. Inverse modeling tools are shown to be a powerful way to systematize and accelerate the process of biogeochemical model interrogation, improving our understanding of model function and the underlying ecosystem biogeochemical processes that they represent.

A large retrospective autopsy study of patients was analyzed to evaluate the major etiologic and pathologic factors contributing to fatal acute pancreatitis (AP). From an autopsy population of 50,227 patients, 405 cases were identified where AP was defined as the official primary cause of death. AP was classified according to morphological and histological, but not biochemical, criteria. Patients with AP died significantly earlier than a control autopsy population of 38,259 patients. Sixty percent of the AP patients died within 7 days of admission. Pulmonary edema and congestion were significantly more prevalent in this group, as was the presence of hemorrhagic pancreatitis. In the remaining 40% of patients surviving longer than 7 days, infection was the major factor contributing to death. Major etiologic groups in AP were chronic alcoholism; postabdominal surgery; common duct stones; a small miscellaneous group including viral hepatitis, drug, and postpartum cases; and a large idiopathic group comprising patients with cholelithiasis, diabetes mellitus, and ischemia. The prevalence of established diabetes mellitus in the AP group was significantly higher than that observed in the autopsy control series, suggesting that this disease should be considered as an additional risk factor influencing survival in AP. Pulmonary complications, including pulmonary edema and congestion, appeared to be the most significant factor contributing to death and occurred even in those cases where the pancreatic damage appeared to be only moderate in extent. Emphasis placed on the early recognition and treatment of pulmonary edema in all cases of moderate and severe AP should contribute significantly to an increase in survival in this disease.

Winter rye (Secale cereale L.) cover crop (RCC) use in corn (Zea mays L.) and soybean [Glycine max. (L.) Merr.] production can alter N dynamics compared to no RCC. The objectives of this study were to evaluate RCC biomass production (BP) and subsequent RCC degradation (BD) and N recycling in a no‐till corn–soybean (CS) rotation. Aboveground RCC was sampled at spring termination for biomass dry matter (DM), C, and N. To evaluate BD and remaining C and N, RCC biomass was put into nylon mesh bags, placed on the soil surface, and collected multiple times over 105 d. Treatments included rye cover crop following soybean (RCC‐FS) and corn (RCC‐FC), and prior‐year N applied to corn. Overall, the RCC BP and N was low due to low soil profile NO3–N. Across sites and years, the greatest BP was with RCC‐FC that received 225 kg N ha−1 (1280 kg DM ha−1), with similar N uptake as with RCC‐FS (27 kg N ha−1). The RCC biomass and N remaining decreased over time following an exponential decay. An average 62% biomass with RCC‐FS and RCC‐FC degraded after 105 d; however, N recycled was greater with RCC‐FS than RCC‐FC [22 (80%) vs. 14 (64%) kg N ha−1, respectively], and was influenced by the RCC C/N ratio. The RCC did not recycle an agronomically meaningful amount of N, which limited N that could potentially be supplied to corn. Rye cover crops can conserve soil N, and with improved management and growth, recycling of crop‐available N should increase.