2022Test1PLSC204studentanswers 2

Comparison of Agronomic Characteristics

Perennial Ryegrass (Lolium perenne)

  • Identification Features:

    • Emerald green colour

    • Ribbed upper leaf surface, shiny or waxy under surface

    • Folded emerging leaf, red colour at tiller base

    • Seed head: compact spike with no awns

  • Growth Form and Function:

    • Temperate C3 grass

    • Prostrate, densely tillered; tiller population of 5000 to 25,000/m²

    • New tillers formed year-round, fastest development in late spring and early summer

    • Compact base with growing point close to soil allows continuous leaf formation

    • Long-day flowering plant; flowers in spring after chilling (vernalisation)

    • Seed head emergence typically around 20th October in New Zealand

  • Yield and Nutritive Value:

    • Faster seed establishment due to larger seeds (2-2.5 mg)

    • Typical DM yield in ideal conditions: 20-25 t/ha

    • Nutritional value: 10-11 MJ/kg DM for green leaf, 8-9 MJ/kg for reproductive stem, 6-7 MJ/kg for dead material

    • Crude protein (CP) content ranges from 12%-25% DM based on nitrogen availability

  • Management Requirements:

    • Requires rotational grazing to prevent damage to growing points

    • Can be improved with endophyte for pest resistance

Cocksfoot (Dactylis glomerata)

  • Identification Features:

    • Dull blue-green leaf colour, very folded tiller

    • Presence of ligule at leaf collar

    • Seed head: spreading panicle, seeds (0.9 mg) have no awns

  • Growth Form and Function:

    • Temperate C3 grass

    • Larger, less dense tillers compared to perennial ryegrass (5000 to 15,000/m²)

    • Adapts growth form based on grazing; can grow taller with lax management or smaller under close grazing

    • Maintains 4-5 live leaves per tiller, allowing for greater herbage mass accumulation

    • Long-day flowering plant; seed heads emerge mid-October to early November

  • Yield and Nutritive Value:

    • Annual DM yield in ideal conditions: 20-25 t/ha

    • More productive than perennial ryegrass under low moisture and fertility constraints (5-6 t DM/ha in dry conditions)

    • Can increase to 21 t DM/ha with irrigation and nitrogen

  • Management Requirements:

    • Requires rotational grazing, especially in spring to prevent reproductive phase which decreases digestibility

    • Tolerant of set stocking but management of growth and grazing is crucial

Comparison of Legumes: White Clover vs. Red Clover

White Clover (Trifolium repens)

  • Features:

    • Most commonly sown legume, suitable for various New Zealand regions

    • Hairless trifoliate leaves with stems (petioles) from stolons o - Flowers in late spring/summer

    • Deep network roots, shallow (20 cm) which limits drought tolerance

  • Growth Form:

    • Stolons allow for spreading and forming clonal plants

    • Highly palatable and nutritious; contributes nitrogen to the soil (25 kg N per 1000 kg of DM)

    • Benefits from rotational grazing and can tolerate set stocking in spring

  • Yield:

    • Typical clover content in mixed pastures: 10-20% of total DM, yield ranges from 7-15 t DM/ha

Red Clover (Trifolium pratense)

  • Features:

    • Considered short-lived perennial (2-4 years)

    • Hairy trifoliate leaves, larger and more oval than white clover, erect flowering stems

  • Growth Form:

    • Deep taproot allows better drought tolerance compared to white clover, less spreading ability

    • Requires recovery period between defoliation

  • Yield:

    • Higher initial clover content in the first few years of mixed swards (20-30% of total DM)

    • Nutritional profile similar to white clover (high ME and CP content) but declines faster over years

Plantain vs. Chicory

Plantain (Plantago lanceolata)

  • Features:

    • Long narrow leaves forming a rosette

    • Compact seed heads on fibrous stem when flowering

  • Survival:

    • Short-lived (3-5 years); sensitive to over-grazing due to crown damage

Chicory (Cichorium intybus)

  • Features:

    • Bigger, paler leaves with distinct mid-rib, slightly serrated edges

    • Deep tap root (up to 1.5 m)

  • Survival:

    • Generally survives 1-3 years, also sensitive to harsh defoliation

Pasture Production Influences by Topography and Abiotic Factors

Topography Effects

  • Aspect:

    • North facing slopes are warmer, promoting early spring production and later autumn production.

    • South facing slopes retain moisture better but face colder temperatures and more frosts.

Climatic Effects

  • Rainfall and Temperature:

    • Rainfall patterns and temperature significantly affect pasture growth rates and species composition.

    • Dargaville experiences frequent rainfall, high pasture production, while Canterbury’s evapotranspiration leads to significant moisture deficits.

Soil Water Holding Capacity (WHC) and Evapotranspiration Rates

  • Growth Pattern Differences:

    • Winton has a uniform rainfall pattern, high dry matter yield (12,000 kg DM/ha)

    • Canterbury experiences low total pasture production (5800 kg DM/ha) due to high ET rates and low soil moisture

Life Cycle of Subterranean Clover

  • Lifecycle Overview:

    • Winter annual; seeds burrow underground during dry summer.

    • Germinates in autumn following rain; requires light grazing to ensure seedling survival.

  • Management Practices:

    • Light grazing post-emergence to ensure reproductive success and accumulate seed for following years.

    • Requires minimal grazing to allow for high yields in subsequent years (optimal growth in milder winters, drier summers).

Factors Affecting Yield

  • Early Autumn Rainfall is crucial for maximizing DM yields. This influences the plant's ability to close the canopy and intercept light effectively.

  • Delayed rainfall leads to lower yield due to prolonged lag phases and poor light interception during critical growth stages.

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