Getting the Correct Plant Population for Root Crop Production: A Grower’s Guide
Achieving optimal plant population is critical for successfully producing root crops like carrots, parsnips, red beet, and sugar beet. Too many plants in a given space can lead to overcrowding, small roots, and competition for nutrients, while too few can result in lower overall yields.
Striking the perfect balance requires understanding crop-specific needs, soil health, and environmental factors. Here’s a guide to help you optimise plant populations for healthier, more marketable root crops.
1. Why plant population matters
The plant population directly affects root size, uniformity, and overall yield. Too dense a population can cause:
- Competition for nutrients and water leading to small, misshapen roots that are out of specification for buyers.
- Increased disease risk due to reduced airflow and higher humidity.
Conversely, under-planting results in:
- Uneven root sizes due to inconsistent access to nutrients and space. This leads to challenges with harvesting, increasing crop losses and damage.
- Reduced yield and profitability from underutilised field space.
2. Determining the ideal population
Plant population is a function of the number of seeds sown, the percentage of germination of the seed batch being sown, and seedling losses up until growth stage 16. Usually, the seed rate is set based on assumptions regarding the seed germination percentage and crop losses based on knowledge and experience.
The optimal plant population varies by crop and production system. Below are general guidelines for common root crops:
| Crop | In-Row Spacing (cm) | Row Spacing (cm) | Plants per Hectare |
|---|---|---|---|
| Carrots | 2.5–5 | 30–45 | 1,000,000–2,500,000 |
| Red beet | 5–10 | 30–45 | 500,000–1,000,000 |
| Sugar beet | 15-20 | 45-50 | 100,000 |
| Parsnips | 5–7.5 | 30–45 | 500,000–700,000 |
Note: Spacing varies based on market preferences for root size, variety, drill specification, soil type, and climate conditions.Adjust populations based on market preferences for size and uniformity.
3. Factors influencing plant population
- Soil type and fertility:
Loose, well-drained soils can support higher plant populations. Test soil regularly to ensure adequate nutrients like potassium, phosphorus, and nitrogen.
- Drill / planter accuracy:
Precision seeding allows for consistent spacing. The reliability and accuracy of seed spacing from a precision drill should be a priority for growers looking to purchase a drill.
Here are the key parameters farmers should look for when choosing a precision seed drill for root crops:
- Adjustable row spacing and in-row accuracy: Ensures consistent seed placement for uniform root development.
- Precise depth control: Allows accurate planting at optimal depths, critical for small-seeded crops like carrots and parsnips.
- High-quality metering system: Accommodates varying seed sizes and shapes while preventing seed damage for accurate singulation.
- Variable-rate seeding: Enables adjustments in planting density based on soil conditions or field variability for optimal yields.
- GPS compatibility: Enhances accuracy, reduces seed waste, and improves overall field efficiency through precise field mapping and coverage.
- Climate and irrigation:
Higher populations may thrive with consistent irrigation and favourable weather. In dry or low-rainfall areas, reduce populations to minimise stress.
- Varietal selection:
Choose varieties bred for high-density planting if aiming for maximum yield per acre. Some varieties produce smaller roots that are better suited for dense populations.
4. Tips for success
- Monitor regularly: Check plant health and adjust irrigation or crop nutrition programmes as needed.
- Use cover crops: Improve soil health and structure to support higher populations by rotating with cover crops.
- Integrated pest management: Densely planted crops may attract more pests and diseases; implement IPM strategies to mitigate.
5. Common challenges and solutions
- Overcrowding:
- Solution: Ensure precise seeding rates and invest in mechanical or hand-thinning.
- Weed pressure:
- Solution: Use pre-emergence herbicides or interrow hoeing to prevent weeds from outcompeting young plants.
- Uneven emergence:
- Solution: Improve soil preparation and consolidation. Seed priming and pelleting can help create more even emergence.
Conclusion
Getting the right plant population for root crop production is both an art and a science. It requires attention to spacing, soil health, and environmental factors. You can achieve higher yields, better-quality roots, and greater profitability by fine-tuning your approach and making adjustments as needed.
Interested in optimising your crop population? Check out our seed population calculator or speak to a team member about Stanhay’s precision seed drills.