Grazing Cover Crops for Soil Health in an Integrated Crop-Livestock System

. Optimizing soil health requires building an environment that creates conditions which allow for best function of the chemical, biological, and physical properties of the soil to thrive as an organism and an ecosystem. Integrated crop-livestock systems (ICLS) use a systems approach to provide improvements to soil health parameters. In the fall of 2021, a randomized complete block study was conducted at the Coastal Plain Branch Experiment Station (CPBES) in Newton, Mississippi and at the Prairie Research Unit (PRU) in Prairie, Mississippi to observe the soil health effects of grazing cereal rye cover crops in a soybean production system. Three treatments were replicated three times across nine paddocks at each location. Treatments included: conventional soybean production respective for each location (CS); cereal rye established as a cover crop for a no-till soybean system (CC); and cereal rye established as a cover crop for a notill soybean system and grazed (GC). Soil health was measured by soil sample analysis and forage production. Soil samples were evaluated for soil respiration, total carbon (TC), nitrogen (N), phosphorus (P), and potassium (K). All paddocks were stocked at approximately 2000 lb ac1 using replacement beef heifers. Forage samples were collected throughout grazing periods and were analyzed for forage mass (FM) and nutritive value (crude protein – CP, total digestible nutrients - TDN) using near-infrared spectroscopy (NIRS). Mean FM from CG paddocks was 999 lb DM ac-1 at CPBES compared to 705 lb DM ac-1 at PRU. CP concentration was 25.6% from CPBES and 15.8% from PRU. Mean TDN was 56.3% at CPBES compared to 57.5% at PRU. Change in mean soil respiration from pre-grazing to post grazing at CPBES was 0.327mg CO2/g soil, 0.308 mg CO2/g soil, and 0.464 mg CO2/g soil in CS, GC, and CC treatments respectively. Change in mean soil respiration from pre-grazing to post grazing at PRU was -0.159 mg CO2/g soil, -0.034 mg CO2/g soil, and -0.072 mg CO2/g soil in CS, GC, and CC treatments respectively. Total carbon mean differences were 0.791mg C/kg soil, 0.953mg C/kg soil, and 1.01mg C/kg soil in CS, GC, and CC treatments at CPBES and were 0.595mg C/kg soil, 0.438mg C/kg soil, and 0.476mg C/kg soil in CS, GC, and CS treatments at PRU. Changes in mean N, P, and K were 0.06 mg N/kg soil, -12.141 mg P/kg soil, and 34.555mg K/kg soil at CPBES and 0.052 mg N/kg soil, 0.518 mg P/kg soil, and 17.409 mg K/kg soil at PRU in CS treatments, 0.082 mg N/kg soil, -3.899 mg p/kg soil, and 29.699 mg K/kg soil at CPBES, 0.032 mg N/kg soil, 0.325 mg P/kg soil, and 9.877 mg K/kg soil at PRU in GC treatments, and 0.082 mg N/kg soil, -3.217 mg P/kg soil, and 36.767 mg K/ kg soil at CPBES, 0.041 mg 0.357 mg P/kg soil, and 7.267 mg K/kg soil at PRU in CC treatments. Differences in nutrient concentrations can be attributed to nutrient cycling of residue from previous growing season and nutrient cycling from grazing heifers. A second year of grazing combined with additional soil sample analysis will help determine the effects grazing a cereal rye cover crop has on soil health of two distinct soils in eastern Mississippi

The Effects of Grazing Cover Crops on Animal Performance and Soybean Production

Grazing cover crops has the potential to offset costs incurred with cover crop establishment, thus incentivizing management adoption. Information regarding cover crop species in combination with grazing and their subsequent effects on soybean production is limited. A field trial was conducted in Newton, MS from 2019 to 2021 to assess these effects. Cover crop treatments included oats (O), O + crimson clover (OC), and OC + radish (OCR) were applied in a randomized complete block design with three replications. Cover crops differed in nutritive analysis; O had significantly lower mean CP, but greater total daily nutrients (TDN). Weaned beef steers grazing cover crops had lower ADG in the OCR treatment (3.03 lb hd-1 d-1), compared to O (3.52 lb hd-1 d-1) and OC (3.55 lb hd-1 d-1). No significant difference was observed in soybean grain yield between cover crop treatments. Mean yields were 51.1, 46.1, and 38.7 bu ac-1 for the O, OC, and OCR treatments, respectively. Total net returns for grazing plus soybean production were significantly lower in the OCR ($817.51 ac-1), compared to the O ($1,107.03 ac-1) and OC ($1,071.15 ac-1) treatments. These returns suggest that grazing provides an added value to cover crop establishment and provides incentives for increased revenue for producers willing to combine livestock and row crop enterprises

Associative Nitrogen Fixation Linked With Three Perennial Bioenergy Grasses In Field and Greenhouse Experiments

© 2020 The Authors. Associative nitrogen (N2)‐fixation (ANF) by bacteria in the root‐zone of perennial bioenergy grasses has the potential to replace or supplement N fertilizer and support sustainable production of biomass, but its application in marginal ecosystems requires further evaluation. In this study, we first combined both greenhouse and field experiments, to explore the N2 fixation effects of three temperate feedstocks Miscanthus × giganteus (giant miscanthus, Freedom), Panicum virgatum (switchgrass, Alamo), and Saccharum sp. (energycane, Ho 02‐147). In field studies across three growing seasons, plant and soil pools of candidate feedstocks were partially composed of N derived from the atmosphere (Ndfa). Energycane, giant miscanthus, and switchgrass were estimated to derive \u3e30%, %Ndfa. Greenhouse studies were also performed to trace isotopically labeled 15N2 into plant biomass and soil pools. Evidence for Ndfa was detected in all three feedstock grasses (using reference 15N of soil, chicory, and sorghum, δ15N~+7.0). Isotopically labeled 15N2 was traced into biomass (during grass elongation stage) and soil pools. Extrapolation of rates during the 24 hr labeling period to 50 days estimated 30%–55% of plant Ndfa, with the greatest Ndfa for energycane. The findings of the field natural abundance and greenhouse 15N2 feeding experiments provided complementary evidence that perennial bioenergy grasses have the potential to support relatively high rates of ANF, and accumulate diazotroph‐derived N into biomass when grown on non‐fertilized soil

Biomass production of herbaceous energy crops in the United States: field trial results and yield potential maps from the multiyear regional feedstock partnership

Current knowledge of yield potential and best agronomic management practices for perennial bioenergy grasses is primarily derived from small-scale and short-term studies, yet these studies inform policy at the national scale. In an effort to learn more about how bioenergy grasses perform across multiple locations and years, the U.S. Department of Energy (US DOE)/Sun Grant Initiative Regional Feedstock Partnership was initiated in 2008. The objectives of the Feedstock Partnership were to (1) provide a wide range of information for feedstock selection (species choice) and management practice options for a variety of regions and (2) develop national maps of potential feedstock yield for each of the herbaceous species evaluated. The Feedstock Partnership expands our previous understanding of the bioenergy potential of switchgrass, Miscanthus, sorghum, energycane, and prairie mixtures on Conservation Reserve Program land by conducting long-term, replicated trials of each species at diverse environments in the U.S. Trials were initiated between 2008 and 2010 and completed between 2012 and 2015 depending on species. Field-scale plots were utilized for switchgrass and Conservation Reserve Program trials to use traditional agricultural machinery. This is important as we know that the smaller scale studies often overestimated yield potential of some of these species. Insufficient vegetative propagules of energycane and Miscanthus prohibited farm-scale trials of these species. The Feedstock Partnership studies also confirmed that environmental differences across years and across sites had a large impact on biomass production. Nitrogen application had variable effects across feedstocks, but some nitrogen fertilizer generally had a positive effect. National yield potential maps were developed using PRISM-ELM for each species in the Feedstock Partnership. This manuscript, with the accompanying supplemental data, will be useful in making decisions about feedstock selection as well as agronomic practices across a wide region of the country

Associative nitrogen fixation linked with three perennial bioenergy grasses in field and greenhouse experiments

© 2020 The Authors. Associative nitrogen (N2)‐fixation (ANF) by bacteria in the root‐zone of perennial bioenergy grasses has the potential to replace or supplement N fertilizer and support sustainable production of biomass, but its application in marginal ecosystems requires further evaluation. In this study, we first combined both greenhouse and field experiments, to explore the N2 fixation effects of three temperate feedstocks Miscanthus × giganteus (giant miscanthus, Freedom), Panicum virgatum (switchgrass, Alamo), and Saccharum sp. (energycane, Ho 02‐147). In field studies across three growing seasons, plant and soil pools of candidate feedstocks were partially composed of N derived from the atmosphere (Ndfa). Energycane, giant miscanthus, and switchgrass were estimated to derive \u3e30%, %Ndfa. Greenhouse studies were also performed to trace isotopically labeled 15N2 into plant biomass and soil pools. Evidence for Ndfa was detected in all three feedstock grasses (using reference 15N of soil, chicory, and sorghum, δ15N~+7.0). Isotopically labeled 15N2 was traced into biomass (during grass elongation stage) and soil pools. Extrapolation of rates during the 24 hr labeling period to 50 days estimated 30%–55% of plant Ndfa, with the greatest Ndfa for energycane. The findings of the field natural abundance and greenhouse 15N2 feeding experiments provided complementary evidence that perennial bioenergy grasses have the potential to support relatively high rates of ANF, and accumulate diazotroph‐derived N into biomass when grown on non‐fertilized soil

Biomass production of herbaceous energy crops in the United States: field trial results and yield potential maps from the multiyear regional feedstock partnership

Current knowledge of yield potential and best agronomic management practices for perennial bioenergy grasses is primarily derived from small-scale and short-term studies, yet these studies inform policy at the national scale. In an effort to learn more about how bioenergy grasses perform across multiple locations and years, the U.S. Department of Energy (US DOE)/Sun Grant Initiative Regional Feedstock Partnership was initiated in 2008. The objectives of the Feedstock Partnership were to (1) provide a wide range of information for feedstock selection (species choice) and management practice options for a variety of regions and (2) develop national maps of potential feedstock yield for each of the herbaceous species evaluated. The Feedstock Partnership expands our previous understanding of the bioenergy potential of switchgrass, Miscanthus, sorghum, energycane, and prairie mixtures on Conservation Reserve Program land by conducting long-term, replicated trials of each species at diverse environments in the U.S. Trials were initiated between 2008 and 2010 and completed between 2012 and 2015 depending on species. Field-scale plots were utilized for switchgrass and Conservation Reserve Program trials to use traditional agricultural machinery. This is important as we know that the smaller scale studies often overestimated yield potential of some of these species. Insufficient vegetative propagules of energycane and Miscanthus prohibited farm-scale trials of these species. The Feedstock Partnership studies also confirmed that environmental differences across years and across sites had a large impact on biomass production. Nitrogen application had variable effects across feedstocks, but some nitrogen fertilizer generally had a positive effect. National yield potential maps were developed using PRISM-ELM for each species in the Feedstock Partnership. This manuscript, with the accompanying supplemental data, will be useful in making decisions about feedstock selection as well as agronomic practices across a wide region of the country

A Randomized Trial Comparing Antibiotics with Appendectomy for Appendicitis.

BACKGROUND: Antibiotic therapy has been proposed as an alternative to surgery for the treatment of appendicitis. METHODS: We conducted a pragmatic, nonblinded, noninferiority, randomized trial comparing antibiotic therapy (10-day course) with appendectomy in patients with appendicitis at 25 U.S. centers. The primary outcome was 30-day health status, as assessed with the European Quality of Life-5 Dimensions (EQ-5D) questionnaire (scores range from 0 to 1, with higher scores indicating better health status; noninferiority margin, 0.05 points). Secondary outcomes included appendectomy in the antibiotics group and complications through 90 days; analyses were prespecified in subgroups defined according to the presence or absence of an appendicolith. RESULTS: In total, 1552 adults (414 with an appendicolith) underwent randomization; 776 were assigned to receive antibiotics (47% of whom were not hospitalized for the index treatment) and 776 to undergo appendectomy (96% of whom underwent a laparoscopic procedure). Antibiotics were noninferior to appendectomy on the basis of 30-day EQ-5D scores (mean difference, 0.01 points; 95% confidence interval [CI], -0.001 to 0.03). In the antibiotics group, 29% had undergone appendectomy by 90 days, including 41% of those with an appendicolith and 25% of those without an appendicolith. Complications were more common in the antibiotics group than in the appendectomy group (8.1 vs. 3.5 per 100 participants; rate ratio, 2.28; 95% CI, 1.30 to 3.98); the higher rate in the antibiotics group could be attributed to those with an appendicolith (20.2 vs. 3.6 per 100 participants; rate ratio, 5.69; 95% CI, 2.11 to 15.38) and not to those without an appendicolith (3.7 vs. 3.5 per 100 participants; rate ratio, 1.05; 95% CI, 0.45 to 2.43). The rate of serious adverse events was 4.0 per 100 participants in the antibiotics group and 3.0 per 100 participants in the appendectomy group (rate ratio, 1.29; 95% CI, 0.67 to 2.50). CONCLUSIONS: For the treatment of appendicitis, antibiotics were noninferior to appendectomy on the basis of results of a standard health-status measure. In the antibiotics group, nearly 3 in 10 participants had undergone appendectomy by 90 days. Participants with an appendicolith were at a higher risk for appendectomy and for complications than those without an appendicolith. (Funded by the Patient-Centered Outcomes Research Institute; CODA ClinicalTrials.gov number, NCT02800785.)

Analysis of Outcomes Associated With Outpatient Management of Nonoperatively Treated Patients With Appendicitis.

Importance: In the Comparison of Outcomes of Antibiotic Drugs and Appendectomy (CODA) trial, which found antibiotics to be noninferior, approximately half of participants randomized to receive antibiotics had outpatient management with hospital discharge within 24 hours. If outpatient management is safe, it could increase convenience and decrease health care use and costs. Objective: To assess the use and safety of outpatient management of acute appendicitis. Design, Setting, and Participants: This cohort study, which is a secondary analysis of the CODA trial, included 776 adults with imaging-confirmed appendicitis who received antibiotics at 25 US hospitals from May 1, 2016, to February 28, 2020. Exposures: Participants randomized to antibiotics (intravenous then oral) could be discharged from the emergency department based on clinician judgment and prespecified criteria (hemodynamically stable, afebrile, oral intake tolerated, pain controlled, and follow-up confirmed). Outpatient management and hospitalization were defined as discharge within or after 24 hours, respectively. Main Outcomes and Measures: Outcomes compared among patients receiving outpatient vs inpatient care included serious adverse events (SAEs), appendectomies, health care encounters, satisfaction, missed workdays at 7 days, and EuroQol 5-dimension (EQ-5D) score at 30 days. In addition, appendectomy incidence among outpatients and inpatients, unadjusted and adjusted for illness severity, was compared. Results: Among 776 antibiotic-randomized participants, 42 (5.4%) underwent appendectomy within 24 hours and 8 (1.0%) did not receive their first antibiotic dose within 24 hours, leaving 726 (93.6%) comprising the study population (median age, 36 years; range, 18-86 years; 462 [63.6%] male; 437 [60.2%] White). Of these participants, 335 (46.1%; site range, 0-89.2%) were discharged within 24 hours, and 391 (53.9%) were discharged after 24 hours. Over 7 days, SAEs occurred in 0.9 (95% CI, 0.2-2.6) per 100 outpatients and 1.3 (95% CI, 0.4-2.9) per 100 inpatients; in the appendicolith subgroup, SAEs occurred in 2.3 (95% CI, 0.3-8.2) per 100 outpatients vs 2.8 (95% CI, 0.6-7.9) per 100 inpatients. During this period, appendectomy occurred in 9.9% (95% CI, 6.9%-13.7%) of outpatients and 14.1% (95% CI, 10.8%-18.0%) of inpatients; adjusted analysis demonstrated a similar difference in incidence (-4.0 percentage points; 95% CI, -8.7 to 0.6). At 30 days, appendectomies occurred in 12.6% (95% CI, 9.1%-16.7%) of outpatients and 19.0% (95% CI, 15.1%-23.4%) of inpatients. Outpatients missed fewer workdays (2.6 days; 95% CI, 2.3-2.9 days) than did inpatients (3.8 days; 95% CI, 3.4-4.3 days) and had similar frequency of return health care visits and high satisfaction and EQ-5D scores. Conclusions and Relevance: These findings support that outpatient antibiotic management is safe for selected adults with acute appendicitis, with no greater risk of complications or appendectomy than hospital care, and should be included in shared decision-making discussions of patient preferences for outcomes associated with nonoperative and operative care. Trial Registration: ClinicalTrials.gov Identifier: NCT02800785