Practical guidance on when to use tine vs disc drills, with specific focus on the underestimated problem of hair-pinning straw residues and the allelopathic effects of decaying cereal straw. Based on James Warne (Soil First Farming) article in Direct Driller Issue 6.
The Hair-Pinning Problem
Disc drills do not cut through chopped straw perfectly at all times:
- Discs tend to push straw and chaff into the slot (hair-pinning)
- Seed is placed on a layer of straw/chaff rather than on firm soil
- In extreme cases, the disc rides out of the ground entirely, placing seed on the surface
- Result: poor seed-to-soil contact, restricted root growth
[Source: dd-issue-06, 2026-04-11]
Allelopathy from Decaying Straw
Scientific research shows that decaying cereal straw releases phytotoxic compounds:
- Acetic, propionic, butyric and phenolic acids
- Decaying straw may also increase the effect of Pythium root rot on establishing crops
Symptoms
- Stunted growth, lack of vigour, discoloured leaves (early, extreme cases)
- By late spring: crops may not tiller, or drop tillers the root system cannot support
- Ultimately: smaller ears and disappointing yield
Why It’s Underestimated
“It’s much easier to attribute disappointing yield to lack of sunshine or rainfall or poor disease control than to something that happened ten months ago and you could have directly contributed to.”
The autumn 2018 drought delayed biological breakdown of straw residues; when spring moisture arrived and biology restarted, toxin release coincided with crop establishment — causing widespread patchiness.
[Source: dd-issue-06, 2026-04-11]
When to Use Each Drill Type
| Situation | Recommended drill | Reason |
|---|---|---|
| Dry residue / cereal straw | Tine drill (default) | Avoids hair-pinning; places seed below residue |
| Large biomass cover crops | Disc drill | Better flow through green biomass |
| Little/no dry lignified residue | Disc drill | No hair-pinning risk |
| Wet conditions with green cover | Disc drill | Soil moisture must be right for either |
“For UK conditions a tine drill should be the default drill of choice, only swapping for a disc drill in situations where a tine drill won’t work.”
Solutions to Hair-Pinning
- Drill choice: use tine drill when drilling into dry residue
- Rotation: diversity is a CA tenet — avoid second cereals where straw toxins are highest risk
- Starter fertiliser: correct choice and timing can alleviate allelopathic effects
[Source: dd-issue-06, 2026-04-11]
Related Pages
- Direct Drills — Types, Manufacturers and Comparisons — Drill types and specifications
- Direct Drill Opener Types — Comparison — Dr Baker’s opener scoring (tine vs disc vs inverted-T)
- Stubble Management and Cutting Height — Straw management and residue handling
- Cover Crops — Cover crops as alternative to cereal-on-cereal