Arachis Glabrata Research Articles

Soil bacterial community response to rhizoma peanut incorporation into Florida pastures.

Incorporating legumes is one option for improving pasture fertility, sustainability, and biodiversity. Diazotrophic microorganisms, including rhizobia that form symbioses with legumes, represent a small fraction of the total soil microbial community. Yet, they can offset nitrogen (N) fertilizer inputs through their ability to convert atmospheric N2 into plant-usable N via biological N2 fixation (BNF). This study used amplicon sequencing of 16S rRNA genes to investigate soil bacterial community composition and diversity in grazed 'Argentine' bahiagrass (Paspalum notatum Flügge) pastures where N fertilizer was supplanted with legume-derived N from BNF in some treatments. Treatments consisted of bahiagrass fertilized with (a) mineral N (224kg N ha-1 yr-1 ), (b) combination mineral N (34kg N ha-1 yr-1 ) and legume-derived N via cool-season clover (CSC) (Trifolium spp.) mix, or (c) combination mineral N (34kg N ha-1 yr-1 ) and legume-derived N via CSC mix and strips of Ecoturf rhizoma peanut (Arachis glabrata Benth.). Bradyrhizobium spp. relative abundance was 44% greater in the mixed pasture. Other bacterial genera with BNF or denitrification potentials were greater in pastures with legumes, whereas sequences assigned to genera associated with high litter turnover were greater in bahiagrass pastures receiving only mineral N. Soil bacteria alpha diversity was greater in pastures receiving 34kg ha-1 yr-1 N fertilizer application and the CSC mix than in pastures with the CSC mix and rhizoma peanut strips. Our results demonstrate soil microbial community shifts that may affect soil C and N cycling in pastures common to the southeastern United States.

SUSTAINABLE FORAGE PRODUCTION IN MELIA AZEDARACH BASED SILVOPASTORAL SYSTEM

Silvopasture experiment was conducted to find out the performance of Melia azedarach (Bakain) with fodder crops in silvopastoral model of agroforestry under rainfed conditions of Ranchi, Jharkhand. Four kinds of fodder grasses viz., Stylosanthes hamata (Stylo), Arachis glabrata (Charabadam), Brachiaria mutica (Para grass) and Pennisetum purpureum x Pennisetum glaucum (NB Hybrid). Maximum growth was seen in Bakain in terms of tree height (185 cm) and collar diameter (24.97 mm) when intercropped with Stylo. Maximum green & dry fodder yield was observed in sole NB Hybrid grass, whereas Charabadam recorded maximum crude protein content in silvopastoral condition. The soil nutrient status of silvopasture was also raised as compared to sole tree/crops.

Establishing rhizoma peanut–bahiagrass mixtures

AbstractRhizoma peanut (RP;Arachis glabrataBenth.) is a perennial legume with ability to persist and spread in mixtures with C4grasses. Most RP establishment studies focus on its use as a monoculture hay crop, and more information is needed on establishment strategies for RP–grass mixtures. The objectives of this study were to compare techniques for establishing RP–grass mixtures and quantify their effects on RP shoot emergence, frequency of occurrence (percentage of quadrats containing RP shoots), percentage ground cover, and RP shoot and root‐rhizome biomass. Treatments were (a) RP planted in monoculture (MRP; control), (b) RP planted simultaneously with bahiagrass (Paspalum notatumFlügge; RP‐BG), or (c) RP strip planted into existing bahiagrass pasture following removal of bahiagrass sod strips (Strip). There was no treatment or sampling date effect on RP shoot density (29.5 shoots m–2) during 10 wk after spring planting. By October, RP ground cover was greater for Strip (43%) than MRP (32%) and for MRP than RP‐BG (18%), and Strip and MRP had greater RP frequency than RP‐BG (82, 72, and 58%, respectively). Strip and MRP (1.39 and 1.10 Mg ha–1, respectively) had greater year‐of‐planting RP shoot mass than RP‐BG (0.52 Mg ha–1), but root‐rhizome biomass was not affected by treatment. Measures of establishment success for Strip generally were equal or superior to MRP, and Strip is a viable option for establishing RP–grass mixtures. Weed competition reduced RP establishment success in RP‐BG relative to the other treatments because herbicides tolerated by both bahiagrass seedlings and emerging RP shoots are unavailable.

Digestibility and nitrogen and water balance in horses fed rhizoma peanut hay.

Rhizoma peanut (RP, Arachis glabrata) hay has the potential to meet horses' crude protein (CP) requirements with less nitrogen excretion than other legumes. This study aimed to evaluate nutrient intake, apparent digestibility, and nitrogen balance of RP "Florigraze" hay compared with alfalfa (ALF, Medicago sativa L. "Legendary XHD") and bermudagrass (BG, Cynodon dactylon L. "Coastal") hays when fed to maintenance horses at 2% body weight/d on a dry matter (DM) basis. We hypothesized that nutrient intake would be comparable between the legume hays and lesser for BG and that RP would result in reduced nitrogen excretion compared with ALF. Six mature Quarter Horse geldings (593 ± 40 kg; mean ± SD) were randomly assigned to one of the hays in a replicated 3 × 3 Latin square with 21-d periods. A 14-d adaptation phase was followed by a 3-d total fecal and urine collection. Days 18 to 21 were used for a companion study. Intake of nutrients is reported on a DM basis. Digestible energy (DE) intakes from ALF (29.91 Mcal/d) and RP (29.37 Mcal/d) were greater (P < 0.0001) than BG (20.78 Mcal/d). CP intake was greater (P < 0.0001) for ALF (2.5 kg/d), followed by RP (1.9 kg/d) and BG (1.5 kg/d). All hays exceeded maintenance requirements for DE, CP, Ca, and P. Apparent digestibility of DM and CP was greatest (P < 0.0001) for ALF (69% and 84%), intermediate for RP (61% and 72%), and least for BG (46% and 64%). Apparent digestibility of neutral detergent fiber did not differ (P = 0.2228) among hays, while digestibility of acid detergent fiber (P = 0.0054) was least for RP but similar for ALF and BG. Water intake (kg/d) for ALF (57) was greater (P = 0.0068) than RP (45) and BG (41). Greater (P = 0.0271) water retention (kg/d) was observed for ALF (13.5), followed by RP (10.8) and BG (7.5). There was a difference in nitrogen excretion, with greatest urinary nitrogen excretion for ALF (P < 0.0001) and greatest fecal nitrogen excretion for BG (P = 0.0001). Total nitrogen excretion was greater (P < 0.0001) for ALF (278 g/d), followed by RP (211 g/d) and BG (179 g/d). Nitrogen retention was greater (P = 0.0005) for ALF when represented as g/d (ALF: 129, RP: 86, and BG: 57 g/d) but similar (P = 0.0377) to RP when presented as percent of nitrogen intake (ALF: 32%, RP: 29%, and BG: 24%). Results indicate that RP hay is a suitable legume for horses by meeting DE and CP requirements and having a significant reduction in nitrogen compared with ALF.

Feeding behavior and preference of horses fed rhizoma peanut hay

Rhizoma peanut (RP, Arachis glabrata Benth) has been used as alternative legume hay for horses; however, feeding behavior and preference of horses fed this hay in comparison to other commonly fed hays warrant investigation. This study aimed to evaluate the feeding behavior and preference of mature horses with maintenance requirements fed RP “Florigraze” hay compared with alfalfa (ALF, Medicago sativa L. “Legendary XHD”) and bermudagrass (BMG, Cynodon dactylon L. “coastal”) hays. Six mature Quarter Horse geldings (593 ± 40 kg; mean ± SD) were used in a replicated 3 × 3 Latin square with 21-day periods. Horses were individually housed in 5 × 4 m stalls bedded with wood shavings. Hays were offered to horses in 46 × 36 cm 66-L rubber-polyethylene containers. Hays were analyzed for chemical composition before the start of the study. After a 14-day diet adaptation, 24-hour behavioral observations were conducted using scan sampling. Time spent feeding, inactive, and at other activities were recorded every 10 minutes. Three-choice preference tests were conducted for a 2-hour duration twice daily on day 20 and 21 by simultaneously presenting 1 kg (as-fed basis) of all 3 hays. Horses’ first choice, hay consumption, and number of times each hay was smelled or tasted but left in preference for another hay were recorded. Preference data were analyzed using descriptive statistics, while behavioral data and hay consumption were analyzed using repeated measures mixed model ANOVA. A hay x time-of-day effect was observed on feeding time (P = 0.0408), and ALF resulted in reduced feeding time 2-4 hours after meals were offered compared to RP and BMG. Daily feeding time was shorter (P < 0.0001) with ALF than BMG (11.7 vs. 8.9 h/d), but RP (9.9 h/d) did not differ from BMG or ALF. Total daily inactivity time was greatest for ALF (P = 0.0037) and similar between BMG and RP. Hay consumption was greatest (P < 0.0001) for ALF (0.996 ± 0.015 kg as-fed/test; mean ± SE), followed by RP (0.935 kg), and least with BMG (0.792 kg). Horses show preference for legumes over grass hay, which might be associated with the higher protein and energy and lower fiber concentration of the hays. Rhizoma peanut has the potential to provide improved welfare by providing decreased inactivity time compared to ALF, while being preferred over BMG. These attributes make RP a suitable forage source for horses.

Herbage responses and nitrogen agronomic efficiency of bermudagrass–legume mixtures

AbstractBermudagrass (Cynodon spp.) is an importantwarm‐season grass for livestock in the southern United States. To be productive, bermudagrass requires supplementary N. This 2‐yr study assessed whether N fertilization could be halved by introducing alfalfa (Medicago sativa L.) or rhizoma peanut (RP; Arachis glabrata Benth.) into ‘Tifton‐85’ bermudagrass monocultures without compromising productivity. Treatments were: bermudagrass, N‐fertilized bermudagrass, alfalfa (‘Alfagraze 600 RR’), RP (‘Florigraze’), and the mixtures bermudagrass–alfalfa and bermudagrass–RP. Mixtures were fertilized with 45 kg N ha–1 harvest–1, whereas N‐fertilized bermudagrass received 90 kg N ha–1 harvest–1. Seven harvests were made each year. Nitrogen‐fertilized bermudagrass and mixtures had similar total herbage accumulation (HA) in 2017, but mixtures produced approximately 3,340 kg DM ha–1 yr–1 less than N‐fertilized bermudagrass in 2016, which had a drier summer. Percentage of alfalfa in the mixtures decreased from 68 to &lt;1% by the end of the study. Rhizoma peanut proportion in mixtures was often low (max. 8%). Nitrogen‐fertilized bermudagrass had the greatest total harvested N in May of 2016 (96 kg N ha–1), but it did not differ from bermudagrass–RP in May of 2017. Nitrogen agronomic efficiency (NAE) was greater for mixtures (27.5 kg DM kg–1 N applied) than for N‐fertilized bermudagrass (21 kg DM kg–1 N applied). Greater NAE in mixtures occurred due to limited response to high N fertilization rates in the N‐fertilized bermudagrass. Further studies on establishment methods, cultivar selection, and management practices are still needed to adopt a successful bermudagrass–legume mixture in northern Florida.

Cover Image, Volume 113, Issue 4

On the cover: Steers grazing strips of rhizoma peanut (Arachis glabrata Benth) and bahiagrass (Paspalum notatum Flüggé) at North Florida Research and Education Center, Marianna, FL, USA. See the article, “Nutrient excretion from cattle grazing nitrogen‐fertilized grass or grass‐legume pastures”, by Garcia et al. in this issue of Agronomy Journal. Photo Credit: Liza Garcia. image

Nutrient excretion from cattle grazing nitrogen‐fertilized grass or grass–legume pastures

AbstractNutrient cycling via livestock excreta is an important grassland ecosystem service. This study was conducted in 2016 and 2017 and determined nutrient excretion from cattle grazing three systems: (a) N‐fertilized bahiagrass (Paspalum notatum Flüggé) overseeded with rye (Secale cereale L.) and oat (Avena sativa L.) during winter (Grass+N), (b) unfertilized bahiagrass overseeded with rye–oat–clover (Trifolium sp.) mixture (Grass+clover), and (c) rhizoma peanut (Arachis glabrata Benth.)–bahiagrass mixture overseeded with a rye–oat–clover mixture (Grass+CL+RP). Urinary volume excreted in the warm season ranged from 122 to 182 L ha−1d−1, more than double that in the cool season (56–70 L ha−1 d−1). Urinary N concentration during the warm season was greater in Grass+CL+RP compared with Grass+N (4.4 vs. 3.1 g kg−1, respectively). In addition, fecal dry matter and organic matter output was greater for Grass+N than for steers grazing Grass+CL+RP during the warm season (3.8 and 3.2 vs. 2.8 and 2.2 kg hd−1 d−1, respectively). Total annual feces excretion concentrations of P, K, Mg, and N were greater in the Grass+N than in Grass+CL+RP system. The introduction of legumes increased the proportion of N returning via urine. However, when summed across seasons, total N excretion (feces and urine) was greater in Grass+N than in Grass+CL+RP (89 vs. 71 kg ha−1 yr−1), mainly due to the greater stocking rate in the former. Grass–legume systems receiving 34 kg N ha−1 yr−1 recycled 80% of the N recycled in the grass system receiving 224 kg N ha−1 yr−1, indicating the potential of forage legumes to add N to grasslands.

Water footprint, herbage, and livestock responses for nitrogen‐fertilized grass and grass–legume grazing systems

AbstractReplacing N fertilizer with forage legumes may increase sustainability of grazing systems. The objectives were to evaluate herbage and animal responses and to quantify the water footprint associated with beef production in N‐fertilized grass or grass–legume systems during 4 yr under continuous stocking. The three year‐round forage systems were: Grass+N which included N‐fertilized bahiagrass (Paspalum notatum Flüggé) during summer which was overseeded with N‐fertilized cereal rye (Secale cereale L.) and oat (Avena sativa L.) during winter; Grass+Clover included bahiagrass without N fertilizer during summer which was overseeded with rye, oat, and a mixture of clovers (Trifolium spp.) during winter; and Grass+Clover+RP included rhizoma peanut (Arachis glabrata Benth.)–bahiagrass mixture during summer which was overseeded with a similar rye–oat–clover mixture as for Grass+Clover. Clover inclusion improved uniformity of herbage distribution throughout the winter. Including rhizoma peanut increased cattle average daily gain (ADG) by 74% during summer. The ADG in Grass+Clover+RP was 0.61 kg d−1 compared with 0.35 kg d−1 on Grass+N and Grass+Clover. The water footprint during summer was less in Grass+Clover+RP than Grass+Clover (18 and 25 m3 kg−1 bodyweight, respectively). Gain per area (GPA) was similar across all treatments through the year, indicating similar productivity in grass–legume and N‐fertilized grass systems. The N‐fertilizer inputs were reduced from 224 to 34 kg N ha−1 yr−1 in Grass+Clover+RP, compared to Grass+N. Inclusion of rhizoma peanut and clovers contributes to developing sustainable grazing systems with reduced levels of off‐farm inputs.

Evaluating Soybean Cultivars for Forage Yield and Nutritive Values

Abstract Alfalfa (Medicago sativa) and perennial peanut (Arachis glabrata) are frequently utilized by equine producers in the Southeast. However, challenges related to their production have producers searching for alternative legume options. In 2019 and 2020, five soybean cultivars, “Tower of Leaves,” “Stonewall,” “Laredo,” “AG79X9,” and “AG64X8,” were evaluated for yield and nutritive value. Soybeans were grown at two row spacings (36 and 71 cm), two locations (Central and South Alabama), and harvested at three heights (10, 15, and 20 cm; HH). Forages were harvested using a plot harvester, dried at 55°C, and ground to 1 mm. Forage quality was determined using a NIRS, with verification by wet chemistry analyses. The study was a randomized, complete block design (n = 4) and statistical analysis was carried out using PROC Glimmix of SAS version 9.4 (SAS Inst., - Cary, NC). Forage yields were greatest in “Stonewall” and “Tower of Leaves,” and lowest in “Laredo” (2,074, 1,978, and 1,348 kg/ha, respectively). Across years, HH and forage cultivar had a significant effect on yield (P &amp;lt; 0.0001). As expected, yield increased as HH decreased (P &amp;lt; 0.0001). In 2019, crude protein (CP) was affected by HH (P &amp;lt; 0.0001), with 10 cm having lower CP than 15 and 20 cm (14 vs 16%, respectively; P &amp;lt; 0.0001). Neutral detergent fiber (NDF), acid detergent fiber (ADF), and total digestible nutrients (TDN) were affected (P &amp;lt; 0.01) by HH and variety. “Stonewall” had the lowest NDF (30.84%) and ADF (29.27%; P &amp;lt; 0.01). “Stonewall” and “AG79X9” had the greatest TDN (74 and 73%, respectively; P &amp;lt; 0.01). The cultivar “Stonewall” shows promise as a forage, with greater yields and moderate forage nutritive value compared with the other cultivars tested. Further research is needed to evaluate “Stonewall” in mixtures with other warm-season annual forages.

94 Feeding behavior and preference of horses fed rhizoma peanut hay

Rhizoma peanut has been used as an alternative legume hay for horses; however, feeding behavior and preference of horses fed this hay warrants investigation. This study aimed to evaluate the feeding behavior and preference of mature horses with maintenance requirements fed rhizoma peanut (RP, Arachis glabrata cv Florigraze) hay compared with alfalfa (ALF, Medicago sativa L. cv Legendary XHD) and bermudagrass (CB, Cynodon dactylon L. cv Coastal) hays. Six mature Quarter Horse geldings (593 ± 40 kg; mean ± SD) were randomly assigned to one of the hays in a replicated 3 × 3 Latin square with 21-d periods. After a 14-d diet adaptation, 24-h behavioral observations were conducted using scan sampling. Time spent feeding, at leisure, and at other activities were recorded every 10 min. Number of chews and bites were counted for 5 consecutive 1-min intervals. Preference tests were conducted on d 20 and 21 for a 2-h duration by simultaneously feeding 1 kg (as-fed basis) of each hay in separate trays twice a day (n = 4 observations/period). Horses’ first choice, hay consumption, and number of times each hay was smelled or tasted but left in favor of another hay were recorded. Hays were analyzed for chemical composition before the start of the study. Preference data were analyzed using descriptive statistics, while behavioral data and hay consumption were analyzed using repeated measures mixed model ANOVA. A hay x time of day effect was observed on feeding time ( P = 0.0393), whereas no hay x time effect was observed on time spent at leisure and other activities. When considering the total hours spent on each behavior, horses fed CB spent more time ( P = 0.0092) feeding compared with ALF (11.7 vs. 8.9 h/d) and less time ( P = 0.0037) at leisure compared with both legume hays. Hay type did not affect total time spent on other activities (1.8 ± 0.23 h/d; mean ± SE). Type of hay had no effect on bite rate (10.7 ± 2.2 bites/min), while horses fed CB had lower ( P = 0.0035) chew rate (71 chews/min) compared with RP and ALF (80 and 81 chews/min). Hay consumption was greatest ( P = 0.0425) with ALF (996 ± 17 g as-fed/test; mean ± SE), followed by RP (935 ± 30 g), and lowest with CB (792 ± 18 g). Digestible energy (Mcal/kg DM) in ALF was 2.58, while in RP was 2.53, and CB was 1.94. Crude protein concentrations in ALF, RP, and CB were 22, 16, and 13.6%, non-structural carbohydrates were 11.4, 10.1, and 7.8%, and neutral detergent fiber was 32.9, 40.4, 66.4%, respectively. Horses show preference for legumes, which might be associated with the nutrient profile of the hays. Rhizoma peanut provides time spent on feeding and chew rates similar to alfalfa.

48 Evaluation of soybean cultivars for forage yield and nutritive qualities

Equine producers frequently utilize legumes, such as alfalfa ( Medicago sativa ) and perennial peanut ( Arachis glabrata ), as forages in their feeding programs. Due to challenges related to production and shipping in the Southeast, producers may be looking for other viable legume options to reduce feeding costs. Soybean ( Glycine max L.) may prove to be a useful option. The current study evaluated 3 forage soybean varieties (V), ‘Tower of Leaves’ (T), ‘Stonewall’ (S), and ‘Laredo’ (L), and 2 grain varieties, ‘AG64 × 8’ (A) and ‘AG79 × 9’ (X), during the 2019–2020 growing seasons for forage yield and nutritive value. Row spacing (RS; 36 and 71 cm), harvest height (HH; 10, 15, and 20 cm), and location [E.V. Smith Research and Extension Center (EVS) and Wiregrass Research and Extension Center (WG)] were also evaluated. Plots were harvested using a small plot harvester. A subsample was dried in a 55°C forced air oven and then ground to 1 mm. Crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) was determined using NIRS analysis. Wet chemistry was performed on 10% of samples for verification. In vitro dry matter digestibility (IVDMD) was determined using batch culture inoculated with an equine fecal matter (10%) and buffer solution (90%) mixture. This study was a randomized, complete block design (n = 4) and stats were analyzed using PROC Glimmix of SAS version 9.4 (SAS Inst., Cary, NC). There was no effect of RS on any parameter evaluated ( P > 0.17). All dependent variables were affected by HH ( P < 0.01), V ( P < 0.01), and location ( P < 0.05). Yield was greatest in S and T ( P < 0.02; 2074 and 1961 kg ha −1 , respectively), while yield was least in L ( P < 0.01; 1340 kg ha −1 ). Neutral detergent fiber and ADF were less in S than L ( P < 0.01; 46 and 37 vs 47 and 38%, respectively), and A ( P < 0.02; 46 and 37 vs 47 and 38%, respectively), while X was also less than L ( P < 0.01; 46 and 37 vs 47 and 38%, respectively) and T ( P < 0.03; 46 and 37 vs 47 and 38%, respectively). Crude protein was greatest in A and X ( P < 0.05; 16.9 and 16.4%, respectively), while it was least in S and T ( P < 0.05; 15.8 and 15.7%, respectively). There was no effect ( P = 0.20) of soybean variety on IVDMD. The EVS location had greater forage yield ( P < 0.0001), CP ( P < 0.0001), and NDF ( P < 0.05), but lesser ADF ( P < 0.0001) than WG. The cultivar S showed the greatest forage yield and the least NDF and ADF, while the CP seen in S was less than other varieties; however, S was only 1% lower than A, which had the greatest CP. This indicates that S has the greatest promise as a forage option and should be further tested in mixtures with other forage species.

50 Intake, digestibility, and nitrogen balance in horses fed rhizoma peanut hay

Rhizoma peanut hay has the potential to meet horses’ crude protein requirements with reduced nitrogen excretion. This study aimed to evaluate nutrient intake, apparent digestibility, and nitrogen balance of rhizoma peanut (RP, Arachis glabrata cv Florigraze) hay compared with alfalfa (ALF, Medicago sativa L. cv Legendary XHD) and bermudagrass (CB, Cynodon dactylon L. cv Coastal) hays when fed to maintenance horses at 2% BW/d on a dry-matter (DM) basis. Six mature Quarter Horse geldings (593 ± 40 kg; mean ± SD) were randomly assigned to one of the hays in a replicated 3 × 3 Latin square with 21-d periods. A 14-d adaptation phase was followed by a 3-d total fecal and urine collection. Intake of nutrients is reported on a DM basis. Both legumes (ALF = 1.99% BW and RP = 1.97% BW) provided DM intake greater ( P < 0.05) than CB (1.82% BW) but were not different from one another. Digestible energy (DE) intake of ALF (29.9 Mcal/d) and RP (29.4 Mcal/d) were greater ( P < 0.05) than CB (20.8 Mcal/d). Crude protein (CP) intake was greater ( P < 0.05) for ALF (2,542 g/d), followed by RP (1,859 g/d), and then CB (1,477 g/d). Alfalfa provided the highest ( P < 0.05) calcium to phosphorus ratio of 6.3:1, while RP provided 4.4:1, and CB provided the lowest (1.7:1). Intake of all hays exceeded maintenance DE, CP, Ca, and P requirements. Apparent DM ( P < 0.05) and CP ( P < 0.05) digestibility were greater for ALF (69%, 84%), followed by RP (61%, 72%), and lowest for CB (46%, 64%). Neutral detergent fiber apparent digestibility did not differ ( P = 0.2228) among the 3 hays, while acid detergent fiber digestibility ( P = 0.0054) was lower for RP and similar for ALF and CB. Apparent digestibility of non-structural carbohydrate ( P < 0.05) was greater for ALF, followed by RP, and lowest for CB, while starch ( P < 0.05) digestibility was similar between the legumes and lowest for CB. Water intake for ALF was greater ( P < 0.05) than RP and CB. Greater urinary excretion ( P < 0.05) was observed for alfalfa, while water excreted through feces was greater ( P < 0.05) for CB, followed by RP, and lower for ALF. Urinary nitrogen (N) excretion was greater ( P < 0.05) for ALF, followed by RP, and lower for CB whereas fecal N excretion for both RP and CB were greater ( P < 0.05) than for ALF. Total N excreted was greater ( P < 0.05) for ALF (278 g/d), followed by RP (211 g/d), and lower for CB (179 g/d). Nitrogen retention was greater ( P < 0.05) for ALF when represented as g/d, but similar to RP when presented as percent of N intake. Results indicate that rhizoma peanut hay is a suitable legume for horses by meeting DE and CP requirements with significantly less N excretion than alfalfa.

Dry matter yield of rhizoma perennial peanut (Arachis glabrata) harvested at six, nine and 12 weeks at two semiarid sites.

Rhizoma perennial peanut (RPP) is a forage legume of excellent adaptability and persistence «»nder subtropical and tropical conditions. Four accessions (USDA-TARS 17033,17050, 17052, and 17097, with PI nos. 276233, 262826, 262833, and 262839, respectively) and two cuitivars (Arbrook and Florigraze) of rhizoma perennial peanut (RPP) in Lajas, and two of the accessions (17033 and 17097) and cultivar Florigraze in Juana Díaz, Puerto Rico, were evaluated for dry matter yield (DMY) under irrigation during a full year.The RPPs were evaluated at six-, nine- and 12-wk harvest intervals (HI) in each of the four seasons of the year. At both sites, yield of accession 17033 was highest (P &lt; 0.01) and averaged 35,779 kg DM/ha/yr. In Lajas, yield of accession 17097 was second best with an average of 30,151 kg DM/ ha/yr, yields of the other four RPPs were similar, averaging 25,374 kg DM/haV yr. Cultivar Florigraze, which produced 16% less than accession 17097 in Lajas, had similar productivity in Juana Díaz. On average, the total yields of accessions 17033 and 17097 and cultivar Florigraze declined (P &lt; 0.01) by about 35 and 27% at the two locations, respectively, as HI increased from six to 12 weeks. Season of harvest had a strong influence on the DMY of RPP. At both locations, 69 and 64% of total yields were produced during spring and summer, respectively. Differences in height among RPPs were significant (P &lt; 0.01) at both locations. Height averaged 26.0,17.6, and 18.5 cm for accessions 17033 and 17097 and cultivar Florigraze, respectively. The great adaptability of RPP to the tropical environment, and its high yield when harvested for hay, make it a crop with the potential of becoming one of the most important forages in the tropics.

Establishment of rhizoma perennial peanut (Arachis glabrata) under irrigation at two semiarid sites in the Caribbean.

Two experiments were conducted to determine time for full establishment of rhizoma perennial peanut (RPP) under irrigation. Experiment one (E1) and experiment two (E2) were conducted, respectively, at the Lajas and Fortuna Substations of the Agricultural Experiment Station of the University of Puerto Rico. At Lajas, rhizomes of accessions USDA-ARS no. 17033, 17050, 17052, 17097 (PI no. 276233, 262826, 262833, 262839, respectively) and cultivars Florigraze and Arbrook, planted at 0.76 and 1.5 m apart in rows, were compared for rate of establishment at 60,120, 180 and 240 days postplanting. At Fortuna, rhizomes of accessions 17033 and 17097, and cv. Florigraze were compared at 80,160, and 240 days postplanting. In E2, plots were subjected to the following weed control methods: (1) manual, (2) mowing, and (3) chemical. Time to full establishment in E1 increased from about six months to eight with an increase in planting distance from 0.76 to 1.5 m. Accessions 17033 and 17097 and cv. Florigraze showed a tendency for faster lateral spread prior to 120 days postplanting than the other RPPs. However, peanut genotypes achieved fufl cover at about the same time. The use of herbicide in E2 was the most effective method for promoting faster cover of RPP plants. Establishment of the stand was achieved prior to 240 days in plots receiving weed control treatments 1 and 3, whereas those receiving treatment 2 achieved only 62.5% cover. Compared to a tropical grass, RPP exhibits a slower pattern of lateral spread and requires a longer time for full establishment when planted under similar conditions. However, reducing planting distance and using herbicides to control weeds are management strategies that can reduce time for full establishment of the RPP stand.

De novo full length transcriptome analysis of Arachis glabrata provides insights into gene expression dynamics in response to biotic and abiotic stresses

The perennial ornamental peanut Arachis glabrata represents one of the most adaptable wild Arachis species. This study used PacBio combined with BGISEQ-500 RNA-seq technology to study the transcriptome and gene expression dynamics of A. glabrata. Of the total 109,747 unique transcripts obtained, >90,566 transcripts showed significant homology to known proteins and contained the complete coding sequence (CDS). RNA-seq revealed that 1229, 1039, 1671, 3923, 1521 and 1799 transcripts expressed specifically in the root, stem, leaf, flower, peg and pod, respectively. We also identified thousands of differentially expressed transcripts in response to drought, salt, cold and leaf spot disease. Furthermore, we identified 30 polyphenol oxidase encoding genes associated with the quality of forage, making A. glabrata suitable as a forage crop. Our findings presented the first transcriptome study of A. glabrata which will facilitate genetic and genomics studies and lays the groundwork for a deeper understanding of the A. glabrata genome.

Litter mass, deposition rate, and decomposition in nitrogen‐fertilized or grass–legume grazing systems

AbstractPlant litter deposition and decomposition play important roles in grassland nutrient cycling. The objective was to evaluate plant litter responses and estimate the N returns via plant litter in contrasting grazing systems, since legume inclusion is hypothesized to result in similar quantities of N return compared with N‐fertilized grass systems. Systems were (a) N‐fertilized bahiagrass (Paspalum notatum Flüggé) during summer with a mixture of N‐fertilized cereal rye (Secale cereale L.) and oat (Avena sativa L.) during winter (Grass+N); (b) bahiagrass (no N fertilizer) during summer and a rye–oat–clovers (Trifolium spp.) mixture + N in winter (Grass+Clover); and (c) bahiagrass (no N fertilizer in summer) with strip‐planted rhizoma peanut (Arachis glabrata Benth.) during summer with a rye–oat–clovers mixture + N during winter (Grass+CL+RP). Litter mass was greatest for Grass+N during October (4,430 kg organic matter [OM] ha−1) and least for Grass+CL+RP in June (490 kg OM ha−1). Litter N concentrations were greatest in Grass+N (16 g kg−1), with similar N concentration for Grass+Clover and Grass+CL+RP litter (14 g kg−1). Contribution of C3 species to litter mass increased from May to July but decreased thereafter. Overall, there was a net return of 47 kg N ha−1 yr−1 via litter across the three systems, and litter decomposition was similar in the three systems. Inclusion of forage legumes during cool and warm seasons in grazing systems has the potential to return similar amounts of N through plant litter deposition as grasses receiving moderate levels of N fertilizer.

Plant growth habit and nitrogen fertilizer effects on rhizoma peanut biomass partitioning during establishment

AbstractRhizoma peanut (RP; Arachis glabrata Benth.) is an important perennial forage legume in the US Gulf Coast region, but propagation using rhizomes and prolonged establishment periods limit its adoption. Genotypes and management practices that hasten establishment are needed. Our objective was to determine the effects of RP growth habit and nitrogen (N) fertilizer application during shoot emergence on biomass partitioning and measures of establishment success during the year‐of‐ and year‐after‐planting. Field experiments were conducted during 2016 through 2018. Treatments were the factorial combinations of two RP entries differing in growth habit (decumbent germplasm Ecoturf and upright cultivar ‘UF Tito’) and three N rates (0, 40, and 80 kg/ha applied 10 weeks after planting [WAP]) arranged in four replications of a randomized complete block design. Upright UF Tito had greater shoot (194 vs. 125 g/m2) and root‐rhizome biomass (249 vs. 111 g/m2) than decumbent Ecoturf at the end of the year of planting. Early growth patterns explained this response in part, as UF Tito had greater leaf area index (LAI; 0.58 vs. 0.39) and lesser root‐rhizome: shoot ratio (0.62 vs. 0.77) than Ecoturf at 20 WAP. Nitrogen fertilization had minimal effects on shoot biomass, and it did not affect root‐rhizome biomass. The entry effect on establishment performance persisted through the year after planting with UF Tito outperforming Ecoturf. Use of an RP genotype that prioritized leaf area and shoot versus root‐rhizome biomass during early growth was more important than N fertilization in expediting RP establishment.

Growth temperature and rhizome propagule characteristics affect rhizoma peanut shoot emergence and biomass partitioning

AbstractAdoption of rhizoma peanut (RP; Arachis glabrata Benth.) is limited by slow establishment. Understanding the factors affecting RP biomass partitioning during the shoot emergence period may aid in developing management practices that enhance establishment. A growth chamber study was conducted to determine shoot emergence and overall growth responses of two RP entries (germplasm Ecoturf and ‘UF Tito’) to day/night temperature (20/10 and 30/20 °C). A greenhouse study evaluated similar responses to rhizome propagule length (10‐ and 20‐cm fragments) and presence or absence of an apical shoot. Shoot emergence was greater (4.9 vs. 2.6 pot−1) at a day/night temperature of 30/20 than 20/10 °C. Root‐rhizome/shoot ratio was much less when RP was grown at 30/20 °C (1.4) than at 20/10 °C (8.5). Growth of more upright‐growing UF Tito was superior to Ecoturf at the greater temperature. In the greenhouse experiment, number of shoots emerged from rhizomes was generally greater with smaller rhizome fragments (10 cm) from which apical shoots were removed, especially for UF Tito. Root‐rhizome/shoot ratio decreased with presence of an apical shoot due to increased shoot biomass, especially for Ecoturf. We conclude that greater growth temperature after planting results in more rapid shoot emergence and greater growth during early establishment, likely favoring summer vs. early spring planting dates, especially for UF Tito. Although RP biomass partitioning responded to presence of an apical shoot on propagules, rhizome length did not affect partitioning and presence of an apical shoot did not consistently influence biomass responses, suggesting no particular requirement for rhizome fragmentation prior to planting.

110 Fecal pH, dry matter and volatile fatty acids of horses grazing legume-grass mixed pastures

Abstract Inclusion of legumes into grass pastures improves pasture quality while significantly decreasing the use of nitrogen (N) fertilizer. Changes in nutritive value of the pasture can affect gut microbiome and health. This study aimed to determine the effects of bahiagrass (Paspalum notatum) pasture intercropped with rhizoma peanut (RP, Arachis glabrata) on forage nutrient composition and fecal variables. Unfertilized bahiagrass (UNF) with no N fertilizer, bahiagrass with 120 kg N.ha-1 (FER), and bahiagrass intercropped with RP and 30 kg N.ha-1 (RP) pastures were evaluated using twelve mature Quarter Horses continuously stocked for 84 days in a randomized block design. Forage and fecal samples were collected every 28 days. Pasture samples were analyzed for nutrient composition by NIR, and fecal samples were analyzed for dry matter (DM), fecal fluid pH and volatile fatty acids (VFA). Data were analyzed using a repeated measure mixed model ANOVA and associations between variables were tested using Pearson’s correlations. Pasture starch was higher (P &amp;lt; 0.01) and non-fiber carbohydrates tended to be higher (P &amp;lt; 0.1) in RP. Hemicellulose and aNDF tended (P &amp;lt; 0.1) to be higher in UNF than in RP. Horses grazing RP tended (P &amp;lt; 0.1) to have greater fecal fluid propionic acid concentration and lower proportion of butyric acid. Proportion of acetic acid was lower (P &amp;lt; 0.05) in FER. Propionic acid concentration was negatively correlated with aNDF (r = -0.55) and ADF (r = -0.52), and positively correlated with ethanol-soluble carbohydrates (ESC, r = 0.55). Butyric acid proportion was negatively correlated with nonstructural carbohydrates (r = -0.70). Horses grazing FER pasture tended to have lower (P &amp;lt; 0.1) fecal DM when compared to RP. Fecal DM was negatively correlated with hemicellulose (r = -0.51), and positively correlated with water-soluble carbohydrates (r = 0.68) and ESC (r = 0.64). Intercropping RP provides pasture nutrient composition superior to UNF and similar to FER with decreased N fertilizer rate, and stimulates positive fermentation outcomes.