The use of winter cover crops (WCC) such as hairy vetch (Vicia villosa Roth) and cereal rye (Secale cereale L.), in a corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation provides long‐term benefits that are generally overlooked. There is a particular lack of information regarding the effects of WCC on soil physical and chemical properties. The objective of this study was to assess the effects of four crop sequences (C/S, corn‐fallow/soybean‐fallow; C‐R/S‐R, corn‐rye/soybean‐rye; C‐R/S‐V, corn‐rye/soybean‐vetch; and C‐R/S‐VR, corn‐rye/soybean‐vetch and rye) under no‐till on several soil physical and chemical properties. Soil chemical properties included soil organic matter (SOM), pH, total nitrogen (TN), nitrates (NO3–N), and available phosphorus (P). The analyzed soil physical properties analyzed were: water‐aggregate stability (WAS), bulk density (Db), penetration resistance (PR), total porosity (TP), pore‐size distribution, water retention properties, and saturated hydraulic conductivity (Ksat). The experimental design was a split‐split‐plot where whole‐plot treatments (sampling period) had a Latin square design and subplot treatments (crop sequences) were arranged in a randomized complete block design with four replications. Compared with winter fallow, crop sequences that included WCC provided substantial benefits from the soil productivity standpoint. Specifically, the use of the C‐R/S‐V or C‐R/S‐VR increased SOM down to 30 cm. All WCC sequences improved WAS with increases of 9, 13, and 17% for C‐R/S‐R, C‐R/S‐V, and C‐R/S‐VR, respectively. Winter cover crop sequences reduced Db and PR of the soil surface and increased total and storage porosity along with plant available water. While the C‐R/S‐V sequence was the most effective in reducing soil NO3–N, the C‐R/S‐R sequence was the most effective in fixing soil P.

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A cooled double crystal monochromator system is used on many high heat load X-ray synchrotron radiation beamlines in order to select, by diffraction, a narrow spectrum of the beam. Thermal deformation of the first crystal monochromatorand the potential loss of beam brightnessis often a concern. However, if downstream beam focusing is planned, the lensing effect of the monochromator must be considered even if thermal deformations are small. In this paper we report on recent experiments at an Advanced Photon Source (APS) beamline that focuses the X-ray beam using compound refractive lenses downstream of an X-ray monochromator system. Increasing the X-ray beam power by increasing the storage ring current from 100 mA to 130 mA resulted in an effective doubling of the focal distance. We show quantitatively that this is due to a lensing effect of the distorted monochromator that results in the creation of a virtual source downstream of the actual source.An analysis of the defocusing and options to mitigate this effect are explored.

Recent increases in corn (Zea mays L.) production in the U.S. Corn Belt have necessitated the conversion of rotations to continuous corn, and an increase in the frequency of tillage. e objective of this study was to assess the e ect of rotation and tillage on soil physical and chemical properties in soils typical of Illinois. Sequences of continuous corn (CCC), 2-yr corn-soybean [Glycine max (L.) Merr.] (CS) rotation, 3-yr corn-soybean-wheat (Triticum aestivum L.) (CSW) rotation, and continuous soybean (SSS) were split into conventional tillage (CT) and no-till (NT) subplots at two Illinois sites. A er 15 yr, bulk density (BD) under NT was 2.4% greater than under CT. Water aggregate stability (WAS) was 0.84 kg kg -1 under NT compared to 0.81 kg kg -1 under CT. Similarly, soil organic carbon (SOC) and total nitrogen (TN) were greater under NT than under CT with SOC values for 0 to 60 cm of 96.0 and 91.0 Mg ha -1 and TN values of 8.87 and 8.40 Mg ha -1 for NT and CT, respectively. Rotations a ected WAS, TN, and K levels with WAS being greatest for the CSW rotation at 0.87 kg kg -1 , decreasing with more soybean years (CS, 0.82 kg kg -1 and SSS, 0.79 kg kg -1 ). A similar pattern was detected for TN and exchangeable K. Results indicated that while the use of NT improved soil quality, long-term implementation of continuous corn had similar soil quality parameters to those found under a corn-soybean rotation.

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