The pros and cons of no-till on arable land

No-till (or zero-till) sows a crop directly into a previous crop’s stubble without any prior topsoil loosening. It has a low level of soil disruption which provides many benefits, especially to soil biology, helping to make soils more resilient.

Overview

Disc-based (no-till) drills cut a slot into the soil, in which the seed (and, sometimes, fertiliser) is placed. Following press wheels close the slot.

The approach requires thorough research on equipment choice and a high standard of crop and soil husbandry.

Factors to consider with disc-based drills:

• They have a greater risk of smear, especially in wetter conditions
• The total weight required for disc penetration increases with disc size
• Discs, which disturb and throw less soil than tines, need less remedial action to produce a level, consistent surface. Angled disc slots are closed by vertical pressure and vice versa

The opener design is critical. This includes the tilt angle of the disc, the drop tube position (relative to a single disc) and whether twin-disc or triple-disc openers are used. The design should avoid ‘hair-pinning’ high levels of residue into the seeding zone.

If needed, many cultivator drills can be used as a direct drill (cultivation elements raised clear of work) or as a cultivator drill. This flexibility is useful when occasional tillage is required (for example, when ploughing ahead of potatoes, sugar beet or peas).

When is no-till suitable?

The approach requires thorough research on equipment choice and a high standard of crop and soil husbandry.

A farm’s suitability for no-till is influenced by the climate, soil and crops.

No-till is more likely to be successful in stable structured (compaction-resistant) soils, such as self-structuring calcareous clays, in lower-rainfall areas. It requires adequate structure (tilth and sub-surface).

Good drainage is essential. However, the structure of sandy and sandy loam soils, especially if low in organic matter, may be unstable; thus, the soil may need occasional loosening.

Pros and cons of a no-till drill

Pros:

• Reduced overall costs (fuel and machinery)
• No other operations – simple to manage in suitable conditions
• Soil structure and biological activity gradually improves (especially earthworm numbers)
• Opportunity to increase area of autumn-sown crops
• High work rates and area capability
• Drilling phased to take advantage of favourable weather conditions
• Stones not brought to the surface
• No compaction below plough furrow
• Reduced erosion, run-off and loss of particulate P
• Better retention of soil moisture in dry areas
• Cope with high levels of residue

Cons:

• Usually needs a specialist, high-cost kit
• Can require careful residue management when drilling (row sweeps)
• All tilth needed for the following crop needs to be naturally made
• Needs good weather and, often, patience to create good tilth – can impose high demand on management where soils are variable
• Drill slot closure can be problematic in certain soils and moisture levels
• High levels of surface residues imply a disc is needed somewhere
• Increased grass weed control problems and heavy reliance on rotations and/or chemicals for weed control
• Crop establishment problems during very wet or very dry spells
• Increased risk of topsoil compaction, especially in wet conditions
• Problems with eradicating residual plough pans
• Risks of increased nitrous oxide (N2O) emissions and leaching of dissolved reactive P
• Unsuited to incorporation of solid animal manures
• Increased risk of fusarium infection and mycotoxins, e.g. deoxynivalenol (DON)

How no-till affects crop yields

No-till can give annual yields of combinable crops within 5% (above and below) of those after ploughing, but there is greater seasonal variability in yield.

Yields are most variable in the first few years of a no-till system.

Immediately after adopting no-till, crop yields may be appreciably lower than after ploughing, but they tend to increase as soil structural conditions improve.

With no-till, soils with poor drainage and weak structure generally give lower yields than after ploughing.

Yield-reducing factors:

• No incorporation of crop residues
• Increase in grass weeds and volunteers
• Increase in some organisms associated with plant diseases
• Increase in slug activity
• Topsoil compaction from previous harvest traffic before soil strength and bearing capacity has increased, especially when associated with poor drainage
• Limited time for the build-up of soil-structure-improving factors (for example, accumulation of organic matter)
• Reduced nitrogen availability (especially in the first few years)

How no-till affects soil

Beneficial changes in some soil properties after the introduction of no-till may be seen within a few months (bulk density and soil strength) or take several years (organic matter levels).

Changes in temperature

• The presence of crop residues keeps the soil cooler and wetter than bare, ploughed soil. This can result in delayed drilling of spring crops

Accumulation of organic matter

• This occurs near the soil surface
• Increases structural stability (resistance to erosion and mechanical actions) and biological activity
• After several seasons, this may lead to a reduced nitrogen requirement

Changes in physical soil properties

• Improved self-structuring at the surface, especially when calcareous, as well as greater water permeability
• The lack of disturbance causes bulk density to increase in the top 25 cm of soil. This can give a wider window for field work, but it can lead to poor aeration and cooler, wetter conditions at the surface

Changes in pH

• The pH of the surface soil can decrease (acidify) to the extent that it contributes to further soil structural deterioration and limits plant productivity

Soil erosion and run-off

• Reduced likelihood of soil erosion and run-off with loss of particulate P, attributed to the lack of soil disturbance and presence of crop residues
• Direct drilling is, therefore, a good means of reducing the risk of nutrient losses by run-off from slopes adjacent to freshwater bodies that are prone to eutrophication
• However, the content of phosphate may increase near the surface, leading to risks of nutrient loss if run-off ever occurs