Industry Knowledge: Tackling Seed Drill Issues with Biostimulant Seed Treatments

With the increasing regulation of conventional pesticides, the use of biostimulant seed treatments to enhance plant growth and resistance is rising as an alternative. The goal is to support germination, early growth, and resilience against biotic and abiotic stresses.

Owing to the physical properties of many biostimulants, some of which are live microorganisms, the formulation and seed application methods can be less sophisticated than farmers may be used to.

Conventional seed treatments are most commonly applied as a flowable concentrate (FS). This quickly dries on the seed surface and does not impact its flowability through seed drills. In comparison, biostimulants are often applied as a slurry, which can be challenging to dry on the seed surface.

This can be problematic for small-seed crops like lettuce, parsnip, onion, and carrot. Slurry-applied biostimulant treatments may lead to unexpected challenges with seed sticking in seed drills, disrupting planting efficiency and uniformity. Here’s a closer look at the issues involved and possible ways to mitigate them.

Understanding Seed Drill Challenges

Seed drills are designed for precision planting, placing each seed at an optimal depth and spacing. However, when seeds treated with biostimulants are sticky, they may clump or adhere to the inner surfaces of the drill. This can lead to:

Blockages in the Seed Drill: Sticky seeds can clog the machinery, interrupting seed flow and causing uneven planting.
Irregular Seed Spacing: If seeds stick together, they may not be spaced evenly, which affects crop uniformity.
Equipment Damage and Maintenance Needs: Frequent blockages increase the risk of wear on the drill components, necessitating more frequent maintenance.

Why Biostimulant Slurries Make Seeds Sticky

Biostimulants like humic acids, amino acids, and various natural extracts can improve seed performance but can also contribute to moisture retention and tackiness when applied as a slurry. This is particularly problematic with fine seeds such as parsnip, onion, and carrot, which are more prone to clumping. As these seeds tend to be small and light, any additional stickiness makes them even more challenging to handle in mechanical drills.

Some contributing factors include:

Moisture Content in the Slurry: Biostimulants are often mixed with water for easy application, but excess moisture can cause seeds to clump together.
Adhesive Properties of the Biostimulants: Some formulations include natural or synthetic binders that help the biostimulant adhere to the seed surface, inadvertently creating a sticky coating.
Seed Surface Area: Smaller seeds have a higher surface area-to-mass ratio, making them more susceptible to the sticky effects of slurry treatments.

Mitigating Seed Drill Issues

While the sticky nature of slurry-applied biostimulants poses challenges, there are strategies to mitigate these issues:

Drying the Seeds Post-Treatment: Allowing treated seeds to air-dry before loading them into the drill can reduce tackiness, making them easier to handle.
Optimising Biostimulant Concentration and Viscosity: Adjusting the concentration and formulation of the biostimulant can help achieve desired effects without excessive stickiness.
Using Alternative Application Methods: For crops where seed drills struggle with slurry-treated seeds, consider dry formulations of biostimulants or integrating them into foliar applications post-germination instead.
Adding a Seed Lubricant: Certain seed lubricants, like talc or graphite, can reduce stickiness in the seed drill. Applied lightly, these can prevent seed clumping and sticking in drills.
Experimenting with Coating Technology: Seed coatings that integrate biostimulants without increasing tackiness are under development, offering a long-term solution for sticky seed issues.

How Stanhay Drills Manage ‘Sticky Seeds’

A seed drill’s features will also significantly affect its ability to manage alternative seed treatments. Here’s how Stanhay’s range copes with seeds treated with biostimulants.

The Stanhay X10 and X30s unique thin disc technology is key and dramatically improves the consistency of seed pickup and release, reducing chance of blockages which are likely when using thick (0.5mm +) seed discs.
Adjustable seed agitators to cope with a variety of different seed types.
A single point singulator will remove the excess seed, leaving one seed per hole.
At the release point a spring assisted brass seed splitter effectively ‘peels’ seed off the disc at the same point vacuum is released to ensure consistent seed drop in the coulter.

Embracing Innovation to Improve Precision Planting

The application of biostimulants continues to offer significant benefits for crop establishment and yield. However, growers and seed technology providers must recognise and address the practical issues associated with their use, especially with small seed crops like parsnip, onion, and carrot. A better understanding of seed handling and the physical properties of these treatments will help prevent issues at planting, promoting healthier, more uniform crop growth from the start.