Single- versus Double-Species Cover Crop Effects on Soil Health and Yield in Mississippi Soybean Fields

Conservation management practices can improve soil health while minimizing deleterious effects of agriculture on the environment. However, adoption of these practices, particularly cover crops, is not widespread, as they often reduce crop yields compared to traditional management practices. The purpose of the current study was to determine if a two-species cover crop treatment of rye (Secale cereale L.) and crimson clover (Trifolium incarnatum L.) could increase soil health parameters and maximize soybean (Glycine max L.) yield greater than rye only in tilled and no-till Mississippi field soils. Enhanced microbial biomass and organic matter input from cover crops increased the activities of β-glucosidase, cellobiohydrolase, fluorescein diacetate hydrolysis, N-acetylglucosaminidase, and phosphatase in surface soils. Rye plus clover tended to elicit higher activities than rye only in no-till plots. Both cover crop treatments inhibited soybean yield in tilled plots by 11–25%. These results indicate that tillage exacerbates yield inhibition by cover crops in soybean and that double-species cover crop treatments were more consistent in increasing activities linked to nutrient cycling. Further study examining different combinations of cover crops in no-till systems is necessary to gain a better understanding of how they can be implemented to enhance soil health while maximizing crop yield.

Soil Enzyme Activity and Stoichiometry: Linking Soil Microorganism Resource Requirement and Legume Carbon Rhizodeposition

Legumes provide multiple ecosystem services in agricultural systems. The objectives of this study were to evaluate the influence of different legumes through C rhizodeposition on the dynamics of C, N and P in soil and on microbial communities’ resource requirements. Legumes pea (Pisum sativum L.), faba bean (Vicia faba L.), white clover (Trifolium repens L.), crimson clover (Trifolium incarnatum L.) and non-legume wheat (Triticum aestivum L.) were grown in pots. Carbon rhizodeposition was quantified by using 13CO2 labeling, and six soil enzyme activities were measured: β-glucosidase (BG), arylamidase (ARYLN), N-acetyl-glucosaminidase (NAG), phosphatases (PHO) and alkaline and acid phosphatases (AKP and ACP). Enzyme stoichiometry approaches were applied. The results showed that BG, NAG and ACP activities were positively influenced by faba bean and clovers. Enzyme stoichiometry analysis revealed a limitation of microorganisms in C and P resources at the plant reproductive stage. These results were explained by plant functional traits. Plant biomass production, root total length, the ability of plants to rhizodeposit C and the C and N content of plant tissues were the main explicative factors. This study also shows that N and C nutrient supplies positively contribute to nutritional requirements and the growth of microorganisms and P availability in soil.

Green manuring with crimson clover as an alternative to mineral fertilization in maize production

Role of mineral fertilizers is to complement the soils’ indigenous supply of minerals for crop plants nutrition. Among the mineral nutrients, nitrogen is generally considered as the most yield-contributing. Obtaining nitrogen from legumes is potentially more sustainable than from industrial sources. Crimson clover (Trifolium incarnatum L.) has long been appreciated as cover crop grown for green manuring due to its capability for binding the atmospheric nitrogen into plant-available form. Green manuring effects of crimson clover for succeeding maize crop were tested in 2019 year on two locations of Northeastern Croatia differing in soil texture: 1) on the site A where the soil was compact and dominated by clay and 2) on the site B where the soil was loose and dominated by loam. The research was conducted in a year with favourable rainfall during maize vegetation. Results have shown that green manuring with crimson clover for maize as the main crop delivered somewhat lower maize grain and aboveground mass yields than the conventional full-dose mineral fertilization on deep fertile soils around Osijek (Northeastern Croatia). When compared to conventional agronomy, green manuring was associated with additional agrotechnical operations required for crimson clover cover crop establishment and its herbage incorporation into soil prior to seeding main maize crop. Research should be continued in more different environments (year × location combinations) in order to produce reliable evaluation of crimson clover’s green manuring services.

89 Fermentation Kinetics of Different Cool-Season Annual Mixtures With or Without Silage Inoculant

High moisture feeds such as baleage are becoming a more practiced feed storage method in the Southeast due to the ability for more timely harvests and consistent forage quality compared with dry hay. The objective of this study was to determine the nutritive quality and fermentation kinetics of three different cool-season annual mixtures stored as baleage. The forage treatments were wheat (Triticum aestivum) + T-Raptor (Brassica rapa × napus; WT), wheat + crimson clover (Trifolium incarnatum; WC), and annual ryegrass (Lolium multiflorum Lam.) + oats (Avena sativa) + crimson clover (ROC) which were planted at the E.V. Smith Research Center in Shorter, AL, as a 3 × 2 × 8 factorial design (n = 3). Forage was either inoculated (I) or not inoculated (N) with a cereal/grass silage inoculant to determine its efficacy in promoting proper fermentation. Samples were taken at 8 different days after ensiling to determine fermentation kinetics and quality. Crude protein of WC was greater (P ≤ 0.005) than all other forage treatments (17.1%) and wheat + crimson clover-I was greater (P = 0.024) than WC-N (17.7 and 16.4%, respectively). However, ROC–N had greater (P = 0.033) CP than ROC–I (16.5 and 15.0%, respectively). Wheat + T-raptor ensiled with the lowest (P ≤ 0.003) pH while ROC had the greatest (P ≤ 0.001; 4.5 and 5.4, respectively). Forage treatments WC and WT did not differ (P = 0.140) in lactic acid concentration (3.7%); however, both were greater (P ≤ 0.001) than ROC (0.9%). There were no differences (P ≥ 0.128) in acetic acid concentration among all forage treatments (3.5%). The results of this study indicate that WC had the greatest nutrient quality, but do not indicate that silage inoculants offer benefits to baleage fermentation kinetics.

64 Effects of grazing cool-season cover crops on forage and animal performance

Utilization of cool-season cover crops has been shown to increase soil health and cash crop performance in minimum tillage cash crop systems. Though evidence that grazing of cover crops can be viable is limited. Our objective was to determine animal and forage performance when grazing a cool-season annual cover-crop. Twelve 1.2 ha pastures were established in a forage mix consisting of black oats (Avena strigose), cereal rye (Secale cereal), crimson clover (Trifolium incarnatum), and T-raptor (Brassica napus × B. rapa) and randomly allocated to be grazed either 0, 30, 60, or 90 days. Three tester steers were randomly placed in each paddock with the exception of control paddocks and allowed ad libitum grazing. Animals were weighed every 30 d for determination ADG and total gain (TG). Forage was harvested bi-weekly and analyzed for NDF and ADF using an ANKOM fiber analyzer (ANKOM Tech, Macedon, NY). All data were analyzed using MIXED procedure of SAS version 9.4 (SAS Inst., Cary, NC). Differences were found in ADG between 90 and 60 days grazed (4.2 ± 0.12 vs. 2.8 ± 0.12 kg/d; P < 0.01) and 90 and 30 days grazed (4.2 ± 0.12 vs 2.7 ± 0.12 kg/d; P < 0.01). Differences in TG were detected between 90 and 60 days grazed (819 ± 13.35 vs. 386.67 ± 13.35 kg; P < 0.01), between 90 and 30 days grazed (819 ± 13.35 vs 261.33 ± 13.35 kg; P < 0.01), and between 60 and 30 days grazed (386.67 ± 13.35 vs 261.33 ± 13.35 kg, P < 0.01). No differences in NDF (44.86%, P = 0.99) or ADF (27.20%, P = 0.92) were detected between treatments. These results indicate that different grazing periods could influence cattle growth and performance without negatively impacting forage quality and production.

65 Effects of grazing cool-season cover crops on forage and animal performance

Utilization of cool-season cover crops has been shown to increase soil health and cash crop performance in minimum tillage cash crop systems. Though evidence that grazing of cover crops can be viable is limited. Our objective was to determine animal and forage performance when grazing a cool-season annual cover-crop. Twelve 1.2 ha pastures were established in a forage mix consisting of black oats (Avena strigose), cereal rye (Secale cereal), crimson clover (Trifolium incarnatum), and T-raptor (Brassica napus × B. rapa) and randomly allocated to be grazed either 0, 30, 60, or 90 days. Three tester steers were randomly placed in each paddock with the exception of control paddocks and allowed ad libitum grazing. Animals were weighed every 30 d for determination ADG and total gain (TG). Forage was harvested bi-weekly and analyzed for NDF and ADF using an ANKOM fiber analyzer (ANKOM Tech, Macedon, NY). All data was analyzed using MIXED procedure of SAS version 9.4 (SAS Inst., Cary, NC). Differences were found in ADG between 90 and 60 days grazed (4.2 ± 0.12 vs. 2.8 ± 0.12 kg/d; P < 0.01) and 90 and 30 days grazed (4.2 ± 0.12 vs 2.7 ± 0.12 kg/d; P < 0.01). Differences in TG were detected between 90 and 60 days grazed (819 ± 13.35 vs. 386.67 ± 13.35 kg; P < 0.01), between 90 and 30 days grazed (819 ± 13.35 vs 261.33 ± 13.35 kg; P < 0.01), and between 60 and 30 days grazed (386.67 ± 13.35 vs 261.33 ± 13.35 kg, P < 0.01). No differences in NDF (44.86%, P = 0.99) or ADF (27.20%, P = 0.92) were detected between treatments. These results indicate that different grazing periods could influence cattle growth and performance without negatively impacting forage quality and production.

Phenotypic and Nodule Microbial Diversity among Crimson Clover (Trifolium incarnatum L.) Accessions

Crimson clover (Trifolium incarnatum L.) is the most common legume cover crop in the United States. Previous research found limited genetic variation for crimson clover within the National Plant Germplasm System (NPGS) collection. The aim of this study was to assess the phenotypic and nodule microbial diversity within the NPGS crimson clover collection, focusing on traits important for cover crop performance. Experiments were conducted at the Beltsville Agricultural Research Center (Maryland, USA) across three growing seasons (2012–2013, 2013–2014, 2014–2015) to evaluate 37 crimson clover accessions for six phenotypic traits: fall emergence, winter survival, flowering time, biomass per plant, nitrogen (N) content in aboveground biomass, and proportion of plant N from biological nitrogen fixation (BNF). Accession effect was significant across all six traits. Fall emergence of plant introductions (PIs) ranged from 16.0% to 70.5%, winter survival ranged from 52.8% to 82.0%, and growing degree days (GDD) to 25% maturity ranged from 1470 GDD to 1910 GDD. Biomass per plant ranged from 1.52 to 6.51 g, N content ranged from 1.87% to 2.24%, and proportion of plant N from BNF ranged from 50.2% to 85.6%. Accessions showed particularly clear differences for fall emergence and flowering time, indicating greater diversity and potential for selection in cover crop breeding programs. Fall emergence and winter survival were positively correlated, and both were negatively correlated with biomass per plant and plant N from BNF. A few promising lines performed well across multiple key traits, and are of particular interest as parents in future breeding efforts, including PIs 369045, 418900, 561943, 561944, and 655006. In 2014–2015, accessions were also assessed for nodule microbiome diversity, and 11 genera were identified across the sampled nodules. There was large variation among accessions in terms of species diversity, but this diversity was not associated with observed plant traits, and the functional implications of nodule microbiome diversity remain unclear.

Low-Carbohydrate Tolerant LAB Strains Identified from Rumen Fluid: Investigation of Probiotic Activity and Legume Silage Fermentation

The objective of this study was to isolate and characterize lactic acid bacteria (LAB) with low carbohydrate tolerance from rumen fluid and to elucidate their probiotic properties and the quality of fermentation of Medicago sativa L. and Trifolium incarnatum L. silage in vitro. We isolated 39 LAB strains and screened for growth in MRS broth and a low-carbohydrate supplemented medium; among them, two strains, Lactiplantibacillus plantarum (Lactobacillus plantarum) RJ1 and Pediococcus pentosaceus S22, were able to grow faster in the low-carbohydrate medium. Both strains have promising probiotic characteristics including antagonistic activity against P. aeruginosa, E. coli, S. aureus, and E. faecalis; the ability to survive in simulated gastric-intestinal fluid; tolerance to bile salts; and proteolytic activity. Furthermore, an in vitro silage fermentation study revealed that alfalfa and crimson clover silage inoculated with RJ1 and S22 showed significantly decreased pH and an increased LAB population at the end of fermentation. Also, the highest lactic acid production was noted (p < 0.05) in LAB-inoculated silage vs. non-inoculated legume silage at high moisture. Overall, the data suggest that RJ1 and S22 could be effective strains for fermentation of legume silage.

The overseeding of two cool-season legumes (Hedysarum coronarium L. and Trifolium incarnatum L.) on switchgrass (Panicum virgatum L.) mature stands increased biomass productivity

In the Mediterranean rainfed systems, perennial warm-season grasses are profitable crops for the production of herbage as forage or feedstock for bioenergy purposes. During summer, when the production of cool-season crops is scarce, warm-season grasses can improve the productivity and stability of forage cropping systems. In Italy, switchgrass (Panicum virgatum L.) can be cultivated for herbage production or as energy crop. The objective of this work was evaluating if relay intercropping with cool-season legumes could be suited to convert a mature stand of switchgrass from energy to dual, energy and forage, production, together with improving the productivity and the quality of the harvestable biomass. All these things considered, a field experiment was carried out in Central Italy, on mature stands of two switchgrass varieties, Alamo and Blackwell, overseeded with two legumes: sulla (Hedysarum coronarium L.) and crimson clover (Trifolium incarnatum L.). The intercropping system was compared with fertilized and un-fertilized pure switchgrass stands. After two years of study, data showed that the intercropping increased the total above ground biomass (AGB) productivity. In the second year, the increase in total AGB production for switchgrass mixtures compared with the pure stands was greater for sulla, a biennial legume, than crimson clover.

Rosmarinus officinalis essential oil as an effective antifungal and herbicidal agent

In order to reduce the use of chemical pesticides, great interest has been focused on environment-friendly biological control agents and botanicals that preserve biodiversity. In this context, our study aimed to assess the antifungal and herbicidal activities of Rosmarinus officinalis essential oil (EO) to find an alternative to synthetic pesticides. The chemical composition of R. officinalis essential oil was determined by gaz chromatography-mass spectrometry analysis (GC-MS). Results showed that R. officinallis EO was rich in monoterpenes and the major constituents were 1,8-cineole (54.6%), camphor (12.27%) and α-pinene (7.09%). However, under laboratory conditions, two tests were carried out. The first one consisted on the study of EO antifungal activity using ELISA microplates and the second one consisted on evaluating the effect of EO on seedling growth of weeds. It was confirmed that this EO significantly inhibits spore germination of Fusarium oxysporum, Fusarium culmorum, Penicillium italicum and at 6 mM, the percentage of inhibition reached 100% on Fusarium oxysporum. Indeed, EO slows down seedling growth of Trifolium incarnatum, Silybum marianum, and Phalaris minor. In fact, EO at 5 mM completely inhibits seed germination. On the other hand, another experiment was carried out to evaluate the herbicidal activity by spraying EO on weeds. This showed that a novel herbicide formulation was set up for the first time to improve the activity of R. officinalis EO on post-emergence. Overall, R. officinalis EO can be suggested as a potential eco-friendly pesticide and suitable source of natural compounds potentially usable as natural pesticides.