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.