Effect of variety and cutting interval on yield and proximate composition of alfalfa (Medicago sativa L.) under irrigation in Central Gondar zone, Ethiopia

Background Understanding the relationship between dry matter yield production and forage quality throughout the growing season will help to optimize the cutting intervals between harvests in different Alfalfa (Medicago sativa L.) varieties. An experiment was conducted to assess the effects of harvest frequency on forage yield and quality of 2 improved cultivars (ILRI-6984 and var. DzF-552) of alfalfa (Medicago sativa L.) in Western Dembia district over 20 months during 2017 and 2018. Four harvest frequencies (every 30, 40, 50 and 60 days) were compared in a randomized complete block design (RCBD) with 4 replications. The experiment was laid down in a randomized complete block design (RCBD) in factorial arrangement with four replications. To assess their production potential plant height (cm), number of branches per plant, fresh biomass yield (t ha−1) and dry matter yield (t ha−1) of the forge and its nutrient content were recorded. The data collected was subjected to analysis of variance (ANOVA) by using the general linear model (GLM) procedure in Statistical Analysis System (SAS) (2003) version 9.1. Results The results revealed that highest forage dry matter yield was recorded for variety ILRI-6984 harvested every 40 days (26.8 t DM ha−1) and for var. DzF-552 when harvested every 60 days (24.1 t DM ha−1) (P<0.001). While crude protein concentration tended to decline as age at harvest increased, there was little consistency in the pattern. Crude protein yields were also inconsistent across treatments but ILRI-6984 harvested every 40 days produced the highest yields (6.5 t ha−1) (P<0.001). Conclusion These preliminary findings need to be confirmed under field conditions on a large scale along with longer-term studies to examine the longevity of the stands at these harvest frequencies. Irregular harvesting based on stage of maturity should be compared with fixed inter-harvest intervals.

Root-To-Shoot Ratios of Flood-Tolerant Perennial Grasses Depend on Harvest and Fertilization Management: Implications for Quantification of Soil Carbon Input

Quantifying soil organic carbon stocks (SOC) is a critical task in decision support related to climate and land management. Carbon inputs in soils are affected by development of belowground (BGB) and aboveground (AGB) biomass. However, uncertain fixed values of root:shoot ratios (R/S) are widely used for calculating SOC inputs in agroecosystems. In this study, we 1) assessed the effect of harvest frequency (zero, one, two, and five times annually) on the root and shoot development of the perennial grasses Phalaris arundinacea (RCG), Festuca arundinacea (TF), and Festulolium (FL); 2) determined the effect of management on the carbon and nitrogen content in AGB and BGB; and 3) assessed the implications of R/S for SOC quantification. We found the highest yields of BGB in zero-cut treatments with 59% (FL)–70% (RCG) of total biomass. AGB yield was highest in the five-cut treatments with 54% (RCG)–60% (FL), resulting in a decreasing R/S with frequent management, ranging from 1.6–2.3 (zero cut) to 0.6–0.8 (five cuts). No differences in R/S between species were observed. Total carbon yield ranged between 5.5 (FL, one cut) and 18.9 t ha−1 year−1 (FL, zero cut), with a higher carbon content in AGB (45%) than BGB (40%). We showed that the input of total organic carbon into soil was highest in the zero-cut treatments, ranging between 6.6 and 7.6 t C ha−1 year−1, although, in the context of agricultural management the two-cut treatments showed the highest potential for carbon input (3.4–5.4 t C ha−1 year−1). Our results highlighted that using default values for R/S resulted in inaccurate modeling estimations of the soil carbon input, as compared to a management-specific application of R/S. We conclude that an increasing number of annual cuts significantly lowered the R/S for all grasses. Given the critical role of BGB carbon input, our study highlights the need for comprehensive long-term experiments regarding the development of perennial grass root systems under AGB manipulation by harvest. In conclusion, we indicated the importance of using more accurate R/S for perennial grasses depending on management to avoid over- and underestimation of the carbon sink functioning of grassland ecosystems.

BIOMASS AND ENERGY CHARACTERISTICS OF MARALFALFA GRASS (Cenchrus purpureus Schumach.) Morrone CULTIVATED IN WARM SUBHUMID CLIMATE TO PRODUCE BIOETHANOL

Biofuels are a sustainable energy option that can contribute to solve some current environmental problems. For example, it seems imperative to find alternative energy sources; and among them adequate and sustainable raw materials to produce biofuels, such as bioethanol. This study, under the assumption that Maralfalfa grass would be a suitable substrate to produce biofuel, aimed at evaluating the biomass yield, chemical composition, and theoretical bioethanol production of Maralfalfa grass (C. purpureus Schumach.) Morrone harvested at three cutting frequencies (CF). Treatments were distributed in a randomized complete blocks design with split-plots arrangement and three replicates. Analysis of variance was done with GLM procedure and means were compared with Tukey test (p≤0.05). At 120 d, the lignocellulosic material content was the highest (p≤0.05) with 66% of holocellulose, 30% hemicellulose, 22% lignin, 1.8% acid soluble lignin, 20% acid insoluble lignin, 26% acid insoluble residue, and 6.2% ashes. The highest concentration of extractives compounds was found at 150 d harvest frequency (15.5%; p≤0.05), while the highest biomass production (32.6 Mg ha-1 y-1), calorific value (21.0 MJ kg-1), and bioethanol production (239.9 L Mg-1 MS-1) was obtained at the 180 d (p≤0.05). No significant changes were found for crude protein (p>0.05). Results showed that Maralfalfa grass (C. purpureus Schumach.) Morrone is an attractive alternative for bioethanol production due to high biomass yield and chemical composition at short harvesting times.

Evaluation of sainfoin (Onobrychis viciifolia) for forage yield and persistence in sainfoin–alfalfa (Medicago sativa) mixtures and under different harvest frequencies

Condensed tannins in sainfoin (Onobrychis viciifolia) improve forage digestion and reduce the risk of ruminant bloat caused by grazing alfalfa (Medicago sativa). The objectives of this study were to evaluate the forage dry matter yield (DMY) and persistence of newer sainfoin cultivars in mixtures with alfalfa, and to determine the impact of harvest frequency on the persistence of sainfoin. Sainfoin cultivars ‘AAC Mountainview’, ‘AAC Glenview’, ‘Delaney’, ‘Shoshone’, and six experimental populations were compared with ‘Nova’ and ‘Melrose’ at Lanigan, SK, from 2016 to 2018. Field plots were seeded in either monocultures of sainfoin at 33 kg·ha−1 or sainfoin–‘AC Grazeland’ alfalfa mixtures at 16:9 kg·ha−1 in alternate rows. Forage DMY was greater (P = 0.001) in mixtures than in sainfoin monocultures in all harvests. The proportion of sainfoin in mixtures at Cut 1 declined from 4.1% to 1.3% of total DMY from 2016 to 2018, and 19.0% to 4.8% in Cut 2, which was less than the recommended level to eliminate ruminant bloat risk. A second field trial was established in 2017 to compare responses of ‘AAC Mountainview’, ‘Nova’, and ‘Shoshone’ sainfoin under one-, two- or three-harvest frequencies in 2018 and 2019. The increase of harvest frequency did not reduce sainfoin stand (%). Stand percentage of ‘AAC Mountainview’ (91%) was greater (P = 0.01) than ‘Nova’ sainfoin (62%). Further agronomic studies focusing on weed control in sainfoin stands and the optimum seeding ratios of sainfoin–alfalfa within the Parkland region of Saskatchewan are needed.

Cultural Control of Drosophila suzukii in Small Fruit—Current and Pending Tactics in the U.S.

Spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), a vinegar fly of Asian origin, has emerged as a devastating pest of small and stone fruits throughout the United States. Tolerance for larvae is extremely low in fresh market fruit, and management is primarily achieved through repeated applications of broad-spectrum insecticides. These applications are neither economically nor environmentally sustainable, and can limit markets due to insecticide residue restrictions, cause outbreaks of secondary pests, and select for insecticide resistance. Sustainable integrated pest management programs include cultural control tactics and various nonchemical approaches for reducing pest populations that may be useful for managing D. suzukii. This review describes the current state of knowledge and implementation for different cultural controls including preventative tactics such as crop selection and exclusion as well as strategies to reduce habitat favorability (pruning; mulching; irrigation), alter resource availability (harvest frequency; sanitation), and lower suitability of fruit postharvest (cooling; irradiation). Because climate, horticultural practices, crop, and market underlie the efficacy, feasibility, and affordability of cultural control tactics, the potential of these tactics for D. suzukii management is discussed across different production systems.

28 Defining Grazing Recommendations for Alfalfa-Bermudagrass Mixtures in the Southeastern U.S

Recently there has been growing interest in interseeding high-quality legumes, like alfalfa, into existing bermudagrass stands as a step towards improving forage, animal, and ecosystem sustainability in the Southeast. Current work evaluating these mixtures has focused on management and production of stored forages, and limited work has evaluated the use of alfalfa-bermudagrass mixtures under grazing conditions. It is known that both grazing intensity and frequency impact overall alfalfa stand production over time. The objective of this research is to evaluate the effect of harvest height and frequency on alfalfa interseeded into bermudagrass to develop grazing management recommendations. In 2018 thirty-six alfalfa-bermudagrass plots were established at 4 locations across Alabama and Georgia in a randomized complete block design with four replications at each location. Alfalfa varieties utilized were selected for suitability to location and were either ‘Bulldog 505’ or ‘Bulldog 805’ interseeded into existing hybrid bermudagrass sods. Treatments included combinations of harvest frequency (2, 4, or 6 weeks) and harvest height (5, 10, 15 cm) and plots were evaluated to determine the optimum interval in relation to sward yield, alfalfa persistence, stand density, botanical composition, nutritive value, and change over time. Forage yield was affected by the interaction of location with harvest frequency and height (P &lt; 0.05). At three of the four locations, overall seasonal yield from the 5cm cutting height was greatest, however alfalfa persistence declined in these treatments throughout the season and was less than 10% at the northern locations when 2019 data collection began. Additionally, crude protein (CP) and in-vitro digestibility (IVDMD) declined throughout the season as the alfalfa presence decreased. This study is supported by funding from the USDA-NIFA-Alfalfa Forage Research Program (2017).

27 Defining Grazing Recommendations for Alfalfa-Bermudagrass Mixtures in the Southeastern U.S

Recently there has been growing interest in interseeding high-quality legumes, like alfalfa, into existing bermudagrass stands as a step towards improving forage, animal, and ecosystem sustainability in the Southeast. Current work evaluating these mixtures has focused on management and production of stored forages, and limited work has evaluated the use of alfalfa-bermudagrass mixtures under grazing conditions. It is known that both grazing intensity and frequency impact overall alfalfa stand production over time. The objective of this research is to evaluate the effect of harvest height and frequency on alfalfa interseeded into bermudagrass to develop grazing management recommendations. In 2018 thirty-six alfalfa-bermudagrass plots were established at 4 locations across Alabama and Georgia in a randomized complete block design with four replications at each location. Alfalfa varieties utilized were selected for suitability to location and were either ‘Bulldog 505’ or ‘Bulldog 805’ interseeded into existing hybrid bermudagrass sods. Treatments included combinations of harvest frequency (2, 4, or 6 weeks) and harvest height (5, 10, 15 cm) and plots were evaluated to determine the optimum interval in relation to sward yield, alfalfa persistence, stand density, botanical composition, nutritive value, and change over time. Forage yield was affected by the interaction of location with harvest frequency and height (P &lt; 0.05). At three of the four locations, overall seasonal yield from the 5cm cutting height was greatest; however, alfalfa persistence declined in these treatments throughout the season and was less than 10% at the northern locations when 2019 data collection began. Additionally, crude protein (CP) and in-vitro digestibility (IVDMD) declined throughout the season as the alfalfa presence decreased. This study is supported by funding from the USDA-NIFA-Alfalfa Forage Research Program (2017).