Effects of Grazing on Nebraska Sandhills Meadow Forage Nutrient Content

Nebraska Sandhills subirrigated meadow pastures were used to measure the effects of grazing on forage nutrient content in summer pastures. Non-grazed pastures had greater diet CP content than grazed pastures early in the grazing season. By late July, grazed vs. non-grazed pastures did not differ in diet CP content. Non-grazed pastures had greater in vitro organic matter disappearance compared with grazed pastures from late July through September; however, early summer pastures were not affected. Observed results indicate the greatest differences in nutrient content between grazed and non-grazed meadow pastures occur early and late in the grazing season when the majority of cool-season grass species growth occurs

Effects of Grazing on Nebraska Sandhills Meadow Forage Nutrient Content

Nebraska Sandhills subirrigated meadow pastures were utilized to measure the effects of grazing on forage nutrient content in summer pastures. Pre-grazed pastures had greater protein and in vitro dry matter digestibility levelsand lower neutral detergent fiber levels compared with post-grazed pastures early in the grazing season. By late July, post-grazed vs. pre-grazed pastures did not differ in in vitro dry matter digestibility and neutral detergent fiber levels. Observed results indicate the greatest differences in nutrient content between post-grazed and pre-grazed pastures occur early in the grazing season

EFFECTS OF STOCKING RATE ON FORAGE NUTRIENT COMPOSITION OF NEBRASKA SANDHILLS UPLAND RANGE WHEN GRAZED IN EARLY SUMMER AND THE EFFECTS OF GRAZING ON NEBRASKA SANDHILLS MEADOW FORAGE NUTRIENT COMPOSTION

The objectives of this research were to 1) evaluate the effects of stocking rate on forage nutrient quality 2) quantify the relative proportions of current vs. previous year growth being consumed in early summer upland range pastures and 3) determine how grazing effects forage nutrient quality in subirrigated meadows in the Nebraska Sandhills. Experiment 1 was a two year study conducted on the experimental upland range paddocks at Gudmundsen Sandhills Laboratory. Twelve 2-hectare paddocks were assigned one of three treatments stocked at 0 (control), 0.57 (light), and 0.85 (heavy) AUM/ha. Ten 0.25 m2 quadrats were clipped per paddock during the study. Diet quality was determined using esophageally fistulated cows. Experiment 2 was conducted at a commercial ranch near Lakeside, NE. Esophageally fistulated cows sampled pastures either grazed or non-grazed throughout the grazing season starting on June 14 and ending late August in a two year study. Samples were analyzed for IVOMD, CP and NDF content. Stocked upland range paddock diet samples had decreased CP, IVOMD, and greater NDF content compared with control paddocks for diet samples. Diet samples were lower in quality compared with current year growth but greater in quality compared with previous year growth indicating cattle consumed previous year growth as part of the diet. Forage accumulation increased linearly in control paddocks but did not change in stocked paddocks. Grazed samples had lower CP content than non-grazed pastures early in the grazing season and unaffected later in the season. Neutral detergent fiber was greater in grazed compared with non-grazed pastures early in the grazing season. Diet IVOMD was most affected by grazing as season progressed. These studies indicate grazing and stocking rate effect diet quality in subirrigated meadows and upland range. Producers need to rotate cattle frequently in early summer to ensure high quality intake. Advisor: L. Aaron Stalker and Terry J. Klopfenstei

Stocking Rate Effects on Forage Nutrient Composition in Early Summer Pastures

Nebraska Sandhills upland range pastures were used to measure the effectsof stocking rate on forage nutrient content in early summer pastures. Stocked pastures had lower CP, in vitroorganic matter digestibility, forage availability, and higher NDF compared with ungrazed pastures. Clipped samples of current year growth had greater CP and in vitro organic matter digestibility than diet samples. Observed results indicate early season grazing decreasesdiet nutrient content and forage availability compared with ungrazed pastures, suggesting that cattle were consuming both current and previous year growth

Coronal Heating as Determined by the Solar Flare Frequency Distribution Obtained by Aggregating Case Studies

Flare frequency distributions represent a key approach to addressing one of the largest problems in solar and stellar physics: determining the mechanism that counter-intuitively heats coronae to temperatures that are orders of magnitude hotter than the corresponding photospheres. It is widely accepted that the magnetic field is responsible for the heating, but there are two competing mechanisms that could explain it: nanoflares or Alfv\'en waves. To date, neither can be directly observed. Nanoflares are, by definition, extremely small, but their aggregate energy release could represent a substantial heating mechanism, presuming they are sufficiently abundant. One way to test this presumption is via the flare frequency distribution, which describes how often flares of various energies occur. If the slope of the power law fitting the flare frequency distribution is above a critical threshold, $\alpha=2$ as established in prior literature, then there should be a sufficient abundance of nanoflares to explain coronal heating. We performed $>$600 case studies of solar flares, made possible by an unprecedented number of data analysts via three semesters of an undergraduate physics laboratory course. This allowed us to include two crucial, but nontrivial, analysis methods: pre-flare baseline subtraction and computation of the flare energy, which requires determining flare start and stop times. We aggregated the results of these analyses into a statistical study to determine that $\alpha = 1.63 \pm 0.03$. This is below the critical threshold, suggesting that Alfv\'en waves are an important driver of coronal heating.Comment: 1,002 authors, 14 pages, 4 figures, 3 tables, published by The Astrophysical Journal on 2023-05-09, volume 948, page 7