Two of the UK’s longest-running field-scale tillage comparison experiments, providing hard evidence on yield and margin impacts of different primary cultivation methods. Based on Nathan Morris, Elizabeth Stockdale, and David Clarke (NIAB) article in Direct Driller Issue 4.
Trial Design
| STAR | NFS | |
|---|---|---|
| Location | Suffolk | Morley, Norfolk |
| Soil | Medium/heavy clay loam | Medium/light sandy loam |
| Started | 2005 | 2007 |
| Scale | 48 plots, 36m × 36m each | Field-scale, fully replicated |
| Rotation | Combinable crops with regular winter wheat | Combinable crops with regular winter wheat |
Three Primary Cultivation Treatments
- Inversion (plough) — ~25cm depth
- Deep non-inversion — ~20–25cm (e.g. Sumo Trio subsoiler/disc combination)
- Shallow non-inversion — ~10cm
- Plus a managed approach — cultivation method changes annually based on conditions
[Source: dd-issue-04, 2026-04-11]
Key Findings — Winter Wheat Yield
STAR (Heavy Clay, Suffolk)
- No difference in average yield between tillage systems across 12 years
- Year-to-year variation (driven by season) far exceeds tillage treatment effects
- Managed approach gives slightly higher average yield than consistent treatments
NFS (Light Sandy Loam, Norfolk)
- Shallow non-inversion shows 4% yield reduction compared to plough/deep (averaged across years)
- Difference is not statistically significant in any individual year
- Lighter soils may be more prone to structure loss without some mechanical intervention
- Managed approach: 4% lower than deep/plough (3 out of 5 years used shallow tillage)
Overall
- Wheat yields are relatively robust across all tillage approaches assessed
- Season (weather) has a far greater impact on yield than tillage method
[Source: dd-issue-04, 2026-04-11]
Key Findings — Gross Margins
- Non-inversion treatments (both shallow and deep) delivered greater margins than ploughing in both trials
- Deep non-inversion: 6–7% margin improvement over plough
- Shallow non-inversion: 1–4% margin improvement over plough
- Managed approach also improved margins versus plough
- Margin advantage driven by lower labour and fuel costs (even where yields were slightly lower)
- Ploughing is also slower → reduced timeliness across the farm area
[Source: dd-issue-04, 2026-04-11]
Other Observations
Soil Structure
- Non-inversion tillage: increasing tightness in upper subsoil over time
- However, large improvements in soil physical conditions observed within a single growing season — driven by the growing crop itself
- Biological structure formation (earthworms, roots) contributes to structural resilience
Organic Matter
- With no change in organic matter inputs: no gains in total carbon storage under non-inversion versus plough (whole profile)
- But organic matter becomes stratified: higher in surface soil, lower at 20–25cm (compared to ploughed plots which distribute OM evenly)
- See Nutrient Stratification in No-Till Soils — this stratification is functional, not problematic
Weeds
- Currently herbicides managing weed burden effectively across all treatments
- Un-treated monitoring areas being established to assess weed seedbank under different cultivation strategies
[Source: dd-issue-04, 2026-04-11]
Related Pages
- No-Till Economics — Benchmarking and Cost of Production — Financial case for reduced tillage
- Conservation Agriculture — Core Principles — Minimum disturbance principle
- Nutrient Stratification in No-Till Soils — OM and nutrient stratification in no-till
- Soil Carbon and Organic Matter — Carbon storage under different tillage regimes
- Direct Drills — Types, Manufacturers and Comparisons — Equipment for non-inversion establishment