pasture science

Faculty of Science - Department of Animal Sciences

Course Description and Faculty Information

  • Course Title: Pasture Science I (PAE115D)

  • Primary Lecturer: Dr. Ndivho Nemukondeni

  • Office Number: Building 5, Office No: 623

  • Consultation Hours: Monday – Friday (10:00 am to 13:30 pm)

Types of Pasture

Cultivated Pasture

  • Definition:

    • Planted and managed by humans through deliberate seed planting or cultivation of forage crops.

  • Characteristics:

    • Types of pasture that are intentionally planted and maintained to produce forage for livestock.

    • Established in areas where natural vegetation is sparse or degraded to complement existing natural pastures,

    • Examples include mixed grasses, legumes, and other forage crops.

Natural Pasture

  • Definition:

    • Vegetation that grows naturally without direct human interventions.

  • Characteristics:

    • Comprises indigenous and native grasses, herbs, legumes, and other plants that adapt to local conditions.

    • Found in areas with minimal human disturbance, such as rangelands, grasslands, forested savannas, and meadows.

Learning Outcomes for Plant Growth and Morphology

Learning Objectives

  • At the end of this learning unit, students will be able to:

    • Demonstrate an informed understanding of the photosynthesis process.

    • Explain the function of plant tillers.

    • Differentiate between plant and animal cells.

    • Understand the importance of plant reserves.

The Grass Plant

Key Components of the Grass Plant

  • Inflorescence

  • Flowering Culm

  • Ligule

  • Leaf Blade

  • Auricles

  • Tiller

  • Collar

  • Stolon

  • Rhizome

  • Daughter Plant

  • Seed

Tillering in Grasses

Definition of Tillering

  • Tillering:

    • The process of producing new shoots or stems from the base of the plants, particularly in grasses.

    • Importance:

    • A high rate of tillering is essential for high production rates.

    • Patterns:

    • Tillering patterns are influenced by species, growing conditions, and management techniques.

Types of Tillers

  • Effective Tiller:

    • Main tillers that contribute to plant productivity.

  • Secondary/Daughter Tiller:

    • Tillers that developed in secondary waves, typically less effective.

  • Suppression of Tillering:

    • Occurs during stem elongation, flowering, and in late flowering perennials, where tillers that develop post-flowering remain small until the next season.

Photosynthesis

Definition

  • Photosynthesis:

    • The biological process by which plants make food from sunlight, water, and carbon dioxide.

    • It converts light energy from the sun into chemical energy in the form of organic compounds, like glucose.

Requirements for Photosynthesis

  • Four Essential Components:

    • Sunlight: Provides energy for the reaction.

    • Water: Absorbed through roots and transported to the leaves.

    • Carbon Dioxide: Enters leaves through stomata.

    • Chlorophyll: The green pigment facilitating the chemical reaction in plants.

Chemical Equation of Photosynthesis

  • Dynamic Chemical Reaction:

    • The general equation for photosynthesis is represented as:
      6CO2 + 6H2O ext{ sunlight, chlorophyll } \rightarrow C6H{12}O6 + 6O2

    • Where:

    • 6CO_2 = Carbon Dioxide

    • 6H_2O = Water

    • C6H{12}O_6 = Glucose

    • 6O_2 = Oxygen

Process of Photosynthesis in Leaves

  • Location in Leaves:

    • Photosynthesis occurs mainly in palisade cells in the leaves.

    • The structure of palisade cells allows efficient absorption of light.

Factors Affecting Photosynthesis

Four Main Factors

  • Light: More light increases the rate of photosynthesis.

  • Water: Insufficient water will slow down the process.

  • Temperature: Optimal range is around 30°C; rates slow beyond 40°C.

  • Carbon Dioxide (CO₂): Higher CO₂ concentrations lead to quicker photosynthesis.

Comparison of Animal and Plant Cells

Differences Between Cell Types

  • Similar Traits: Both cell types possess cytoplasm, a nucleus, and a cell membrane.

  • Plant Cells:

    • Distinguishing features include:

    • Cell Wall: Provides structural support.

    • Chloroplasts: Involved in photosynthesis.

    • Large Vacuole: Used for storage and maintaining turgor pressure.

Main Nutrients for Plants

Essential Nutrients

  • Nitrates:

    • Needed for protein synthesis.

  • Phosphates:

    • Provide phosphorus for photosynthesis and respiration processes.

  • Potassium:

    • Enhances the function of enzymes needed during photosynthesis and respiration.

Energy Production, Storage, and Utilization

Overview of Energy Dynamics

  • Photosynthesis Site in Plants:

    • Leaves are the primary site of photosynthesis.

  • Utilization of Photosynthates:

    • Systematic regions utilize the carbs produced; excess carbohydrates are stored in parts like stolons and roots.

  • Regrowth Post-Defoliation:

    • Energy reserves are critical for regrowth after grazing or cutting.

Factors Influencing Energy Reserves

  • Environmental Factors:

    • High temperatures and low soil moisture stress negatively impact carbohydrate reserves.

    • Optimal nitrogen levels enhance reserves if managed correctly.

Defoliation Effects on Grass Growth

Influences of Defoliation

  • Dependence on Factors:

    • Age and stage of leaf matter, percentage of leaf matter removed, and extent of total leaf area affected.

  • Impacts of Severe Defoliation:

    • Results in a loss of production, longer recovery times, and potential plant death.

Graze Management Recommendations

  • Best Times to Graze:

    • Proper timing is critical for maximum grass production and health.

Summary and Self-Assessment

Review Questions

  1. Differentiate between cultivated and natural pastures.

  2. Define the photosynthesis process and its equation.

  3. Describe the tillering process and its importance.

  4. List the four main components required for photosynthesis.

  5. Discuss the main nutrients necessary for plant growth.

  6. Explain the functions of plant reserves.

  7. Illustrate and label the growth and regrowth of grass.

  8. Define defoliation and the factors it depends on.

Conclusion

  • Final Note: The comprehensive understanding of pasture science will contribute significantly to enhancing livestock productivity and sustainable pasture management practices.