Pasture Grasses - Dr Alistair Black_default

Objectives of the Lecture

• Focus on Pasture Grasses: Describe common pasture grasses in New Zealand, especially sown species, emphasizing their ecological roles and contributions to livestock production.

• Identification and Management: Understand plant morphology, ecological adaptations to climatic and edaphic factors (temperature, moisture), and their influence on pasture management strategies.

Identifying Pasture Grasses

• Field Identification: Importance of physically examining grass tillers for key features, such as leaf arrangement, blade width, and inflorescence, which are crucial for accurate species identification.

• Resources: Massey University's Pasture Plant Identification website serves as a valuable tool for obtaining photographs and enhancing identification skills across diverse grass species. Additionally, local agricultural extension services offer workshops on pasture identification and management.

• Morphology Impact: The growth form of grasses, including tillering ability, root depth, and leaf structure, significantly influences their persistence, grazing management requirements, and overall productivity across different environments.

Key Factors in Grass Management

• Climatic Factors:

  • Temperature: Optimal growth ranges and its effects on photosynthesis and recovery after grazing.

  • Moisture: Importance of rainfall patterns and irrigation management in sustaining pasture health.m

• Edaphic Factors:

  • Soil Fertility: Discusses the impact of nutrient availability on pasture productivity.

  • Grazing Management: Effective rotational grazing strategies can enhance soil health and grass persistence.

  • Grazing Tolerance and Pest Tolerance: Traits that influence each grass species' ability to thrive despite stressors.

• Yield Considerations:

  • Annual Dry Matter Yields: Quantitative assessments of forage production vital for livestock feeding decisions.

  • Seasonal Distribution of Production: Understanding peak growth periods to optimize livestock intake during critical seasons.

  • Nutritional Values: Key indicators such as Metabolizable Energy (ME), crude protein content, fiber levels, and digestibility that influence animal health and productivity.

Ryegrass Overview

• Key Types:

  • Perennial Ryegrass (Lolium perenne): Most commonly sown grass in New Zealand pastures, favored for its productivity and adaptability.

  • Hybrid Ryegrass, Italian Ryegrass, and Annual Ryegrass (Lolium multiflorum): Each has unique attributes such as growth rate, persistence, and seasonal growth patterns that cater to specific farming needs.

• Ryegrass Characteristics:

  • Perennial ryegrass is classified as a true perennial, needing medium to high fertility soils for optimal growth. It exhibits moderate drought tolerance but may suffer during prolonged dry conditions.

  • Establishment of perennial ryegrass is relatively easy, with an array of cultivars available that incorporate novel endophytes to enhance pest resistance and overall resilience.

• Identifying Ryegrass:

  • Key visual characteristics include emerald green, shiny leaves; a folded emerging leaf at the tiller base; and distinctive reddy-purple coloration that may appear under stress. Knowledge of these traits simplifies the identification process in the field.

Cultivars of Ryegrass

• Seed Companies: R A G T New Zealand is notable for developing ryegrass cultivars with varied traits, including enhanced disease resistance and improved nutritional profiles.

• Performance Differences: Significant variations in tiller density, growth profiles, and flowering times are noted among different cultivars, impacting grazing management practices. The choice between diploid and tetraploid varieties influences both pasture recovery and livestock performance.

Alternative Grass Species

• Tall Fescue (Lolium arundinaceum):

  • A perennial grass that exhibits excellent drought tolerance and requires high fertility. Sensitive to heavy grazing pressures but may contain beneficial novel endophytes (e.g., MaxP) that improve pest resistance.

• Meadow Fescue (Lolium pratense):

  • More suited for colder winter conditions, exhibiting a prostrate growth habit that can enhance productivity in drier environments.

• Cocksfoot (Dactylis glomerata):

  • Adapted to medium fertility and drought-prone conditions, cocksfoot is persistent under dry land situations but has a slow establishment rate that requires careful planning.

• Brome Grasses:

  • Comprise various species including grazing brome (Bromus stamineus), pasture brome (Bromus valdivianus), and prairie grass (Bromus willdenowii), each differing in grazing tolerance and drought resistance.

• Others:

  • Timothy (noted for its slow establishment but high quality) and Phalaris (known for its drought tolerance but potential health issues when overgrazed).

Summary of Key Grass Species

• Ryegrass: The most commonly sown species, lauded for its ease of establishment and the diversity of cultivars available, providing multiple management options.

• Tall Fescue: An alternative suited for wetter or warmer climates, capable of responding beneficially to improved grazing management practices.

• Cocksfoot: The second most widely sown species, recognized for its persistence in various conditions and effectiveness in drought scenarios.

• Brome Grasses: More persistent than ryegrass in many environments, yet less commonly chosen in modern sowings due to various management challenges.

Resources for Further Reading

• Comprehensive textbooks: "New Zealand Pasture and Crop Science" and "Pasture and Forage Plants for New Zealand" are recommended for in-depth understanding and guidance on pasture management practices.