Grazing Management Effects on Plant Growth and Development Notes

The lecture by Dr. Alastair Black focuses on how grazing management affects the growth of plants, especially pasture species like perennial ryegrass and white clover. The goal is to understand how plant structure influences their survival and quality of food they produce.

Key Concepts in Grazing Management

• Plant Structure: Understanding plant parts (like tillers in grasses and stolons in clover) is important because these parts help the plants survive and grow.

• The health of ryegrass and white clover relies on keeping these growth parts intact.

Defoliation and Its Effects

• Grazing, or defoliation, changes how well plants grow and survive, so managing grazing effectively helps improve plant health.

Literature Review Reference

• A valuable source is a review by Grant Edwards and David Chapman, found in a special publication by the New Zealand Grassland Association. This resource discusses how pasture plants grow and respond to grazing.

Clonal Plant Species Reproduction

• Both perennial ryegrass and white clover reproduce in two ways: asexually (through growth parts) and sexually (by seeds).

• Asexual reproduction helps maintain better pasture quality.

• Stolons: Horizontal stems of white clover that can grow roots and leaves at different points.

• Tillers in Ryegrass: Each ryegrass tiller has about 3-4 green leaves; when new leaves grow, older ones die off.

Managing Grazing for Plant Growth

• Proper grazing management supports the growth of new tillers and stolons. This is vital for the plants' recovery after grazing.

GrassView Software

• GrassView is a software developed at Massey University that shows how pasture grows back after grazing and how sugar levels change with leaf growth.

Carbohydrate Reserves after Grazing

• After grazing, sugar content in plants drops as it is used for new leaf growth. Continuous short grazing results in lower growth rates and can lead to plant death.

Clover Management and Grazing

• How we manage grazing affects clover levels. Intensive grazing usually increases white clover content in summer, while lighter grazing can reduce it.

• An experiment showed that sheep under rotational grazing kept more clover during dry summers than those that were set stocked.

Different Cultivars and Pasture Types

• Various white clover types (like Tahoure, Hue, Pitau, Kopu) respond differently to grazing methods, affecting their survival in pastures.

Comparing Grazing Systems

• Set stocking (allowing continuous grazing) often results in more tillers compared to rotational grazing, which helps pasture withstand different weather. Yet, the overall pasture yield and animal production are similar in both systems.

Managing Environmental Stress

• Research indicates that continuous stock grazing benefits white clover during drought by promoting more branching stems.

Finding Research Publications

• Useful sources for research include the Journal of New Zealand Grasslands and Lincoln University Library, helpful for finding articles on grazing strategies and pasture management.

Conclusion

• Good grazing management is crucial for keeping pasture species healthy and productive. Key seasons like spring are important for boosting plant growth, which leads to better pasture quality.