Sustainable Soil Management - Reduced Tillage

What is a real-word example of the soil erosion issue?

In the Great Plains of the US, dust bowl winds eroded the topsoil from 65 million hectares of land.

What are the impacts of tillage on soil physical properties?

1) Exposes the soil surface -> increased risk of erosion & surface crusting (water barrier). Widens soil temperature ranges

2) Breaks up soil aggregates -> increased risk of wind & water erosion, exposes organic matter to oxidation

3) Soil compaction -> creates plough pan. Reduces water infiltration, weakens root growth & reduces nutrient uptake.

What are the impacts of tillage on soil biology?

1) Removes plant cover -> interrupts the flow of root exudation (input of OM) into the soil

2) Inverts the soil -> destroys biopore channels (e.g. made by worms). Biologically active surface layer is buried under the sub surface layer

3) Increases microbial respiration -> nutrients released & soil OM consumed.

What is zero tillage?

Drilling straight onto the old crop, without ploughing/clearing the land first. Means there is no soil disturbance, and it increases residue cover from previous crops, improving soil structure & protecting it from erosion.

How much carbon has been lost from farming land?

The world's soils have lost a total of 133bn tonnes of carbon since humans first started farming the land around 12,000 years ago (Sanderman et al., 2017).

What steps are involved in carbon cycling in soils?

1) Carbon is added to soil through root exudation or deposition of leaf/root litter

2) Microbial activity makes carbon bioavailable through metabolic processes

3) Carbon is either respired into the atmosphere, or sequestered (enters the stable carbon pool as microbial necromass).

How does the structure of a uncultivated (0 tillage) soil compare to a cultivated soil?

. More micropores

. Crop residue on surface

. Plough pan being biologically broken down - roots can pass through

. Root/earthworm channels undisturbed.

What are the effects of zero tillage on soils over time?

. It reduces global warming potential -> mostly due to decreases in CO2. This becomes much more significant after approx 11-15 years

. Soil porosity decreases in the first few years

. Soil structure regenerates after 5 years

. Microbes create aggregates that preserve carbon

. Increases soil aggregate stability (particles held together stronger).

What are the challenges of this zero tillage approach?

1) Direct drill machines often cost £20,000-£30,000 -> so skipping tillage and drilling directly into the crop is very expensive! Although you are saving money in labour costs...

2) Problems with use of herbicides, e.g. Glyphosate (the most commonly used herbicide worldwide) -> has toxicity and health risks, causing the EU to ban it (2022). This ban has been extended until at least December 2025, due to the Plant Protection Production Regulations 2019 as part of the EU exit strategy.

What factors affect damage from tillage?

Time of the year, depth/frequency of cultivation, soil moisture and texture.