In-Depth Notes on Forage Brassicas

  • Speaker: Doctor Alastair Black

  • Focus: How forage brassicas can help pasture production in New Zealand

  • Learning Objectives: Learn about dry matter yields, nutritional values, and how to manage forage crops.

Importance of Forage Crops

  • Livestock Production: Most farms depend on pastures, and animals graze outside all year.

  • Use of Forage Crops: These crops provide extra food when pastures are low, like in winter or during summer dry spells.

  • Common Forage Crops: Brassica plants are popular for this purpose and help restore pastures.

Role in Pasture Systems

  • Pasture Renewal: This means rotating from old pastures to annual forage crops and then back to new pastures.

  • Winter Forage Crop: Important for pregnant ewes to ensure they get enough nutrition during long winters, especially in areas like Western Southland.

  • Weed Management: Growing forage brassicas helps manage weeds and improve soil fertility.

Brassica Species Overview

  • Common Brassica Varieties: Examples include swedes, kale, rape, bulb turnip, and leafy turnip.

  • Growing Cycle: Most brassicas grow for two years. They focus on leaves in the first year and produce seeds in the second year unless harvested.

  • Season Classification: Brassicas can be summer, autumn, or winter/spring feeds.

Characteristics of Common Brassicas

  • Swedes: Bulb plants that store energy well.

  • Kale: Has thicker stems and more leaves than rape.

  • Rape: Common for summer grazing, ready to feed 60-100 days after planting.

  • Bulb Turnip: Used for winter feeding; varieties like Barkant are great for summer pasture recovery.

  • Leafy Turnip: A hybrid plant between turnip and rape that is flexible and drought-resistant.

Growing Conditions for Brassicas

  • Summer to Autumn: Rape can be planted in regions with low rainfall, typically in October, and takes about 60-100 days to mature. Bulb turnips can also supplement summer feed.

  • Winter Options: Kale is planted late in the year (November-December) and can yield up to 20 tonnes of dry matter per hectare. Swedes can yield the same, suited for cooler climates.

  • Turnips: Can be planted anytime from early to late summer, with yields influenced by type and conditions.

Nutritional Profiles

  • Different brassicas have varied nutrients:

    • Kale: High in fiber but may have less protein in winter.

    • Swedes: High energy from the bulbs.

    • Turnips: Mix of bulb and stem provides good nutrition for maintaining cattle weight.

Grazing Management

  • Controlled grazing is necessary to prevent damage to the crops.

  • Rotate pastures seasonally for better growth and quality.

New Developments in Brassicas

  • Rafano Brassica: A hybrid that shows promise for drought resistance and allows multiple grazing opportunities while repelling pests.

  • Research Findings: New hybrids can outperform traditional varieties—like Palatone Rafano yielding 16 tonnes compared to 11 tonnes for leafy turnips.

Conclusion

  • Selection Criteria: It's crucial to match crop choices with growing conditions and animal feed needs.

  • Recommended Readings: Check textbooks on New Zealand pastures and articles on forage science.

Key References

  • Supplementary feeding systems in the New Zealand Pasture and Crop Science textbook.

  • Pasture and Forage Plants in New Zealand.

  • Resources from the Forage Brassica Development Group.