Leaving Cert Agricultural Science – Higher Level sample questions

Topic: Grassland, Grazing, Reseeding, and Conservation

Section A: Short Answer Questions (10 marks each)

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1. List three reasons why a farmer would choose to reseed a grassland field.

  • Low ryegrass content – Poor-quality grasses reduce productivity.
  • Weed infestation – Invasive weeds reduce grazing efficiency.
  • Soil compaction & poor drainage – Limits root growth and nutrient uptake.

    • 2. Explain two advantages of using a multi-species sward in grassland management.

    1. Higher mineral content – Improves animal nutrition and performance.

    2. Clover fixes nitrogen – Reduces fertiliser costs and enhances soil fertility.

    3. Describe two ways in which grass growth and productivity can be improved through grazing management.

    1. Rotational grazing – Allows grass to recover and regrow efficiently.

    2. Maintaining optimal stocking rates – Prevents overgrazing and soil damage.

    4. What is the optimal pH for grassland, and why is it important for plant growth?

  • pH 6.0-6.5 is ideal for grass growth.
  • Ensures nutrient availability, particularly phosphorus and nitrogen.

    • 5. Outline the key differences between silage and hay in terms of conservation and nutritional value.

  • Silage is fermented, has higher moisture content, and retains more nutrients.
  • Hay is dried, stores well but has lower protein and energy content.

    • 6. Explain why wilting grass before ensiling improves silage quality.

  • Reduces moisture content, lowering the risk of effluent runoff.
  • Increases sugar concentration, improving fermentation.

    • 7. What is meant by the term “tillering” in grass growth, and how does grazing influence it?

  • Tillering is the production of new shoots, increasing grass density.
  • Grazing at lower heights encourages tillering and promotes regrowth.

    • 8. Why is clover an important component in a grass reseeding mixture?

  • Fixes atmospheric nitrogen, reducing the need for chemical fertilisers.
  • Improves palatability and digestibility of forage.

    • 9. Describe the main differences between paddock grazing and strip grazing.

  • Paddock grazing: Land divided into 20-30 paddocks, with stock moved regularly.
  • Strip grazing: Grass is allocated in narrow strips using electric fencing.

    • 10. Explain why silage effluent must be properly stored and managed on farms.

  • Highly polluting – Can cause water contamination.
  • Must be stored in sealed tanks to prevent runoff.

    • Section B: Structured Questions (50 marks each)

    Question 1: Reseeding and Establishment of Grassland

    (a) List and explain four factors that should be considered before reseeding a grassland field. (12 marks)

    1.Soil fertility – Conduct soil tests for pH, phosphorus (P), and potassium (K) levels.

    2. Weed infestation – Control weeds before reseeding.

    3. Drainage issues – Poor drainage can affect grass establishment.

    4. Reseeding method – Choose based on soil conditions and machinery availability.

    (b) Describe the steps involved in preparing a seedbed before reseeding. (10 marks)

    1. Take soil samples to assess nutrient requirements.

    2. Plough and harrow the field for a fine seedbed.

    3. Apply lime and fertiliser to optimise soil conditions.

    4. Roll the soil after sowing to improve seed contact.

    (c) Compare direct sowing and direct drilling as methods of grass establishment. (10 marks)

    Compare direct sowing and direct drilling as methods of grass establishment.

    (d) Explain why the choice of grass seed mixture is important for livestock performance. (8 marks)

  • Perennial ryegrass (PRG): High yield, persistent.
  • Clover: Improves nitrogen levels.
  • Diploid vs. Tetraploid: Tetraploids have higher digestibility, but diploids last longer.

    • (e) Outline two ways in which farmers can maintain high productivity in a newly reseeded field. (10 marks)

    1. Correct fertilisation – Follow soil test recommendations.

    2. Graze young grass lightly to encourage tillering.

    Question 2: Grazing Systems and Grassland Productivity

    (a) Describe how a paddock grazing system is managed, and list two advantages and two disadvantages of this system. (12 marks)

  • Land divided into 20-30 paddocks; animals moved every 24-48 hours.

    • Advantages: Fresh grass daily, prevents overgrazing.

    Disadvantages: High setup costs, difficult to cut silage.

    (b) Compare block grazing and strip grazing in terms of efficiency and management. (10 marks)

    Block grazing: Larger sections grazed for 1 week, less fencing required.

    Strip grazing: Smaller sections grazed daily, better grass utilisation.

    (c) Explain how rotational grazing improves grass utilisation and regrowth. (10 marks)

  • Ensures grass regrowth before re-grazing.
  • Maximises grass utilisation and prevents wastage.

    • (d) Why is zero grazing used on some farms, and what are two benefits and two drawbacks of this system? (10 marks)

  • Grass is cut and transported to housed animals. It can be a useful option during periods of poor weather, or when seasonal shortages reduce grazing availability.

    • Benefits: No poaching, more efficient use of grass.

    Drawbacks: Labour-intensive, high machinery costs.

    (e) Outline how a leader-follower grazing system works and explain its benefits for young stock. (8 marks)

  • Young stock graze first, older animals follow.

    • Benefits: Improves grass quality for younger stock and reduces worm burden.

    Section C: Extended Response Question (50 marks each)

    Question 3: Conservation of Grass for Winter Feeding

    Grass is conserved during the growing season to provide feed during winter months. Discuss:

    (a) The biological process of silage fermentation and how bacteria play a role in preservation. (10 marks)

  • Lactobacillus bacteria convert sugars into lactic acid, reducing pH to 3.8-4.2.
  • Clostridium bacteria cause poor fermentation (pH >4.8), producing butyric acid.

    • (b) The importance of dry matter (DM) percentage in silage and how it is determined. (10 marks)

  • Higher DM means better fermentation and lower effluent runoff.
  • Ideal silage DM: 25-30% for pit silage, 30-35% for bales.

    • (c) The role of additives in improving silage quality and the types of additives used. (10 marks)

    Silage additives are natural or manufactured products that can be added to or applied onto the crop at harvesting in liquid or solid form to improve the efficiency of silage preservation at different stages from fermentation to feeding.

    Molasses: Increases sugar for fermentation.

    Acids: Lower pH quickly to prevent spoilage.

    Bacterial inoculants: Speed up fermentation.

    (d) The advantages and disadvantages of using round bale silage versus pit silage. (10 marks)

    The advantages and disadvantages of using round bale silage versus pit silage.

    (e) How farmers can reduce environmental risks associated with silage production. (10 marks)

  • Store silage effluent in sealed tanks to prevent water pollution.
  • Wilt grass before ensiling to reduce runoff.
  • Use biodegradable bale wrap to minimize plastic waste.

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