Management (Leaving Cert Agricultural Science): Revision Notes

Management

Introduction and uses of grass

Grassland serves two essential purposes in Irish agriculture. First, it provides direct grazing and immediate nutrition for livestock during the summer months. Second, it can be harvested and stored to supply winter fodder throughout the winter period when grass growth is minimal.

Understanding grass management is crucial because all livestock enterprises that raise cattle or sheep depend entirely on grass for productivity. Like any crop such as barley or potatoes, grass requires careful attention and management to achieve maximum production potential.

The National Grass Growth Curve shows how grass production varies dramatically throughout the year in Ireland. Peak growth occurs in late spring and early summer, with significantly reduced growth during winter months. Weather patterns like the 2018 drought can severely impact grass production, creating challenges for farmers in providing adequate feed.

Livestock units

To properly budget grass resources, farmers need to understand two key elements: expected pasture production and livestock consumption requirements. The amount each animal consumes varies greatly depending on the animal type, gender, and age. To simplify calculations, we use Livestock Units (LU) - a standardised system where each animal receives a unit value based on its characteristics.

Livestock units allow farmers to measure the total grazing pressure in a pasture and calculate both the annual green herbage (grass) needed for the herd and the winter fodder requirements.

Grazing systems

The grazing system determines how farmers move livestock to maximise grass utilisation while allowing grazed areas to recover. Most systems are rotational, based on moving animals between different areas so livestock get access to fresh grazing while pastures rest and recover between grazing periods.

Rotational grazing

In rotational systems, animals move around throughout the grazing season. After each area is grazed, it's allowed to recover before being grazed again in the next rotation. The rotation might involve entire fields or divided sections within larger fields.

Block grazing

Block grazing divides large fields into smaller, independently grazed blocks. It's similar to strip and paddock grazing, but animals remain on each block for longer periods (one week or more), whereas strip and paddock systems involve daily animal movement.

Advantages of block grazing:

• More economical due to reduced fencing and labour costs
• Less labour intensive than strip or paddock grazing
• Suitable for part-time farmers or when daily labour is limited

Disadvantages of block grazing:

• Less efficient than paddock or strip grazing
• Results in more wastage of quality grass

Strip grazing

Strip grazing divides fields into long, narrow strips, with each strip containing approximately 24 hours worth of grass. Electric fences define each strip and move daily to provide fresh grazing areas.

The system requires both back fencing to prevent animals returning to previously grazed strips, and front fencing to control access to fresh grass. Water sources must be mobile (moved daily) or accessible via a permanent pathway back to troughs.

Advantages of strip grazing:

• Fresh grass always available with no wastage
• Animals cannot return to previously grazed pasture, allowing proper recovery

Disadvantages of strip grazing:

• Requires significant daily management and attention from farmers
• Moving fences and water sources daily is extremely labour intensive
• Fixed water sources can be problematic

Paddock grazing

Paddock grazing divides available space into equal-sized paddocks, each containing one day's worth of grazing. The system requires at least 21 paddocks to allow grass 21 days recovery time before re-grazing.

Advantages of paddock grazing:

• Fresh grass always available with no wastage
• Potential for silage production from excess grass
• Paddocks can recover properly between rotations

Disadvantages of paddock grazing:

• Requires extensive fencing, multiple water sources, and access to each paddock - expensive to establish
• Demands significant management and attention
• Very small paddocks are difficult to cut for silage

Set stocking

Set stocking involves no pasture division - farmers know the field size and release animals at a set rate per unit area. This system works best on very large areas, rough grazing, or areas with difficult daily access.

Advantages of set stocking:

• Inexpensive - no mobile fencing or water sources required
• Low labour and maintenance requirements
• Minimises poaching and density issues as stock spreads out

Disadvantages of set stocking:

• Not very effective for grass utilisation - animals may be selective in grazing
• Quality grass may get trampled and damaged
• Ungrazed grass becomes stemmy and unpalatable
• Constant exposure to pests and diseases

Zero grazing

Zero grazing means exactly what it sounds like - animals never enter pastures. Instead, grass is cut by machine and brought to livestock housing, where animals consume fresh grass but remain housed year-round.

Zero grazing is also called ex-situ grazing and works well when animals are permanently housed. Catch crops can supplement zero grazing systems.

Advantages of zero grazing:

• No poaching or land compaction
• Energy not wasted on animal movement, resulting in higher live weight gain and milk yields
• Distance from farmyard not an issue
• No water sources or fencing needed in fields

Disadvantages of zero grazing:

• Extremely labour intensive for farmers
• Costly in terms of labour and diesel expenses

Complementary grazing systems

These animal management systems work alongside rotational systems rather than replacing them. For instance, creep grazing might be used within a paddock rotational system.

Creep grazing

Creep grazing allows young animals (ewes and lambs, or suckler calves and dams) to graze together. The paddock is subdivided so young animals access fresh grass areas that adults cannot reach. This is typically achieved by installing gates too small for adults to pass through, while young animals move freely between adult and creep areas.

Advantages of creep grazing:

• Young animals can suckle for extended periods
• Young animals access fresh grass for improved weight gain
• Farmers can provide additional concentrate rations in creep areas that adults cannot access
• Reduces disease and parasite buildup in young animals

Disadvantages of creep grazing:

• Similar to block grazing, mobile fencing and water source costs can be high
• Can be labour intensive if combined with strip grazing requiring daily fence movement

Leader follower grazing

Leader-follower grazing extends rotational systems and works with any rotational approach. Unlike creep grazing, young and older animals occupy separate paddocks throughout the rotation. Young animals graze each pasture first, then older animals follow to the pasture just vacated by the younger group.

Advantages of leader-follower grazing:

• Freshest grass goes to youngest animals to support growth
• Farmers avoid disease and parasites in young animals since they graze ungrazed pasture without parasite eggs
• Following with older animals maximises grass usage, as they consume grass left by young animals

Disadvantages of leader-follower grazing:

• Same disadvantages as other rotational systems
• Costly with extensive mobile fencing and water sources
• Labour intensive if animals and fencing move daily

Mixed grazing

Mixed grazing combines cattle and sheep grazing the same pasture simultaneously. Note that sheep and goats cannot graze together as they share similar endoparasites. This system exploits the differences between sheep and cattle grazing patterns and parasite types.

Advantages of mixed grazing:

• No grass wastage since sheep are less selective than cattle, increasing pasture productivity and meat output
• Mixed grazing reduces internal parasite numbers in each species due to lower host animal density and different parasite types between cattle and sheep
• Production of each animal type increases by 10-15%
• Closer cropping by sheep increases tillering for improved next rotation production

Disadvantages of mixed grazing:

• Lower density of each animal type means fewer cattle per hectare than cattle-only grazing
• Same disadvantages as the underlying rotational system regarding cost and labour

Extended grazing

Extended grazing keeps animals grazing outdoors longer into the period when they would normally enter winter housing (December to March). This can significantly reduce the enterprise's carbon footprint.

Advantages of extended grazing:

• Reduces winter housing and feeding requirements, greatly increasing profit margins since winter housing and feeding is expensive
• Reduces silage and concentrate needs, meaning more grass available for grazing and less reliance on market prices for concentrate feeds
• Makes enterprises more sustainable and reduces carbon footprint

Disadvantages of extended grazing:

• Autumn and winter grass quality is poorer, potentially affecting livestock live weight gain
• Weather conditions can make land unusable due to flooding or poaching
• Winter grazing means closing pastures early, reducing available pasture for normal late-year grazing
• Can decrease ryegrass proportion in pastures, with more annual meadow grass and other lower-nutrient grasses

Fertilising grassland

Grass grown for livestock requires careful maintenance and management like any crop. This sometimes means fertilising grassland similar to tillage fields to maintain maximum output. Grass needs relatively high nitrogen levels, especially under intensive grazing.

Nitrogen application

One dairy cow (one livestock unit) produces 85kg nitrogen per year. Using LU calculations similarly to herbage needs, a herd with 10.2 LU total would produce 867kg nitrogen annually spread across multiple land hectares.

The grazing sward composition should be considered when calculating nitrogen needs - clover presence reduces nitrogen requirements.

Fertiliser application always follows soil testing and responds to soil index results. When soil index is sufficiently high, no additional fertiliser is needed.

Phosphorus application

Additional fertilisers are only applied after soil testing, and only when soil index shows soil deficiency in particular nutrients. This prevents fertiliser overuse.

Phosphorus application depends on soil index - at index 4, no additional phosphorus is needed. Like nitrogen, phosphorus requirements depend on stocking rate.

At the highest stocking rate (211-250 kg/ha/yr) with the lowest soil index (1), maximum phosphorus application would be 39kg/ha.

For grass cut for silage with no grazing, at the poorest index (1), maximum phosphorus is 40kg/ha before first cut and 10kg/ha before second cut.

Indirect impacts of grassland management

The primary goal of grassland management is optimising grass production amount and quality. Grass is needed for year-round livestock feeding, either as grazed grass or winter fodder.

Each management action in different grazing systems aims to maximise grass production amount, grass quality, and efficiency of grass utilisation by livestock. However, grassland management can have additional effects on animals and environmental outcomes.

Impacts on livestock

Grassland management serves as a tool to reduce disease and decrease endoparasites:

• Parasites such as nematodes and liver fluke don't reach high levels when stock avoid grazing the same land area permanently
• Rotational grazing breaks endoparasite life cycles when sufficient time exists between rotations
• Disease is minimised when animals don't graze around their own dung
• Mixed grazing results in higher growth rates for both sheep and cattle when grazed together
• Mixed grazing helps decrease parasite loads in cattle since sheep don't share identical parasites
• Creep grazing (dedicated areas for lambs or calves) allows calves continued access to mothers for suckling while providing access to fresh grass

Impacts on wildlife

Pesticide and herbicide use:

• How farmers apply agrochemicals significantly affects wildlife, particularly pollinators
• Generally not a major problem with grazing grassland management, as using these chemicals would harm livestock

Fertiliser use:

• Excessive nitrogen fertiliser application reduces soil invertebrate diversity - there may be higher invertebrate abundance in over-fertilised soil, but limited to one or two species
• Run-off from poorly applied fertiliser can enter waterways causing eutrophication
• Diversifying grazing swards (adding clover) to minimise additional nitrogen requirements directly benefits pollinators and other insects

Ploughing and reseeding grassland:

• Decreases biodiversity when old permanent pasture is replaced with new leys
• Less impact when pastures are reseeded with diverse grass and clover mixtures
• Ploughing negatively impacts soil structure and soil invertebrates

Intensive grazing effects:

• High stocking rates can result in high nitrogen amounts on pastures
• High stocking rates often cause soil compaction
• Both factors are detrimental to biodiversity

Sward height effects:

• Semi-natural and rough grazing support the highest bird and butterfly diversity
• Closely cropped grass dramatically decreases invertebrate numbers, creating knock-on effects up the food chain
• Spiders are usually extremely abundant in grassland but require taller stem length
• Farmers are encouraged to plant diverse meadow plants to increase sward height and biodiversity

Health and safety

Agricultural Science focuses significantly on working safely, requiring health and safety considerations in every enterprise. Most points apply to both grassland management and general livestock enterprises.

Working with livestock

Livestock hazards are relevant to grassland management since farmers must handle livestock to move them between pastures.

Hazard: The livestock (cattle or sheep) that farmers move between paddocks in grazing systems

Risk: Being kicked, trampled, crushed, bitten, and injuries from horns

Working with fertilisers

Hazard: The fertiliser itself - fertilisers are harmful agrochemicals that tend to be strongly oxidising and can cause serious physical harm

Risk: Fertilisers can cause skin and eye irritation and burning, plus respiratory system inflammation. High nitrate fertilisers represent fire hazards when combined with other materials. Fertiliser decomposition can release dangerous chemicals such as ammonia.

Working with machinery

Hazard: Vehicles and machinery used to fertilise, plough, and reseed grassland

Risk: Being crushed or struck by machines, being pinned or thrown from tractors, falling from tractors or machines, entanglement in PTO, injury from moving parts/blades

Electric fencing

Electric fencing establishes rotational grazing systems and can be moved daily.

Risks:

• Danger of shocks to persons or machines - serious injury risk is highest with prolonged shocks or shocks applied to head or neck
• Danger of entanglement in fencing