Allerton Project: reducing compaction in no-till systems

BACKGROUND

Reducing compaction in no-till systems

Carbon dioxide emissions from soils were 132% higher in ploughed soil than in less disturbed soils. © Felicity Crotty/GWCT

The Allerton Project at Loddington is one of 16 study sites across Europe for the EU-funded SoilCare project. The project will test soil management practices intended to increase farm business profitability, while also delivering environmental benefits. Our local farmer network helps to set the research agenda to ensure that the research is relevant to their interests and needs. They considered compaction in reduced and no-till systems to be a widespread problem that has negative impacts on crop profitability and soil function. It also has a negative impact on flood risk and water quality by accelerating runoff and erosion. SoilCare is an EU-funded project which is exceptional in that the exact experimental research to be carried out was not specified in the contract. Instead, much of the first year involved applying a structured approach, in collaboration with social scientists, to enable local farmers to set the research agenda by prioritising topics that would be of most value to them. Our local farmers considered compaction in reduced and no-till systems to be a widespread problem that has negative impacts on crop profitability and soil function. It also has a negative impact on flood risk and water quality by accelerating runoff and erosion.

We set up a replicated experiment with three replicates per treatment at the Allerton Project in the barley (2018) and field beans (2019) stages of the rotation. The means of compaction alleviation that we tested were traditional ploughing and the use of a low disturbance subsoiler (LDS). A third treatment involved the use of a mycorrhizal inoculant which was not expected to influence physical soil properties, but could improve crop nutrient uptake through the fungal strands. The experimental area was deliberately compacted by driving a tractor up and down at right angles to the tramlines before the alleviation methods were applied, and we evaluated the three methods against control plots in which the crops were direct drilled without any form of compaction alleviation.

The SoilCare project is concerned with wider environmental considerations, as well as the crop performance and economic considerations of the farmers and so a wide range of data were collected. Most notably, the SoilCare project enabled us to buy innovative equipment to monitor greenhouse gas flux associated with the various treatments so that we could assess their implications for climate change.

Carbon dioxide flux (exchange and movement of the gas) varied seasonally, being around 130% higher in the summer than in the winter. Due to the high variation in carbon dioxide flux no significant treatment differences were found, but there was a strong trend with CO² emissions; 132% higher in the plough plots. Nitrous oxide flux was significantly (P=0.042) higher in the non-cultivated plots. However, even considering the much higher (298 times more than CO²) global warming potential of nitrous oxide, the global warming potential of these emissions were very low across all plots when compared with the carbon dioxide results. These findings are important as we were concerned that anaerobic (low oxygen) conditions associated with direct drilling and compacted ground may have resulted in higher nitrous oxide flux than in plots where the soil had been disturbed. As well as higher carbon dioxide emissions from the soil, the act of ploughing and subsequent cultivations is also associated with additional emissions of greenhouse gases through the increased burning of diesel fuel.

Water infiltration rates showed no significant differences but were highest in the plough and subsoiled plots in 2018, but lowest in the plough plots in 2019. Earthworm

KEY FINDINGS

densities were significantly (P=0.046) affected by the plot treatments and were highest in the inoculated plots in 2018 and in the control plots in 2019, being lower in the treatments with more soil disturbance in both years (see Figure 1). Infiltration rates can be higher in ploughed than undisturbed direct drilled soil because of the initial more open structure, but can also be higher in direct drilled soil where high earthworm densities create channels through which infiltration can take place. However, in our experiment, earthworm densities were 69% lower in 2019 than in 2018, not higher, so this relationship between soil management and infiltration rates requires further investigation.

Crop yields did not differ significantly between treatments in the beans or barley, but showed a trend towards being higher in plough (8.15t/ha) and LDS (7.99t/ha) than inoculated (6.64t/ha) and control (6.58t/ha) plots in the barley. There was little difference in net income from barley because of the costs associated with cultivations, but in the beans, the control and inoculated plots were associated with about 25% higher net margins.

This research has improved our understanding of the environmental and economic implications of alleviating compaction in our arable rotation; information that we are already sharing with the farmers who suggested this work, and much more widely.

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Earthworm number per m² (+ 1 se)

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100 The Gasmet GHG analyser monitors greenhouse gas flux in the crop. © Jenny Bussell/GWCT

Carbon dioxide emissions from soils were 132% higher in ploughed soil than in less disturbed soils.

There was no difference in bean yield, but barley yield was 20% higher in plough and LDS (subsoiled) plots.

Owing to differences in cultivation costs the beans had approximately 25% higher net margins in the direct drill plots.

There was little difference in net income from barley.

Chris Stoate Felicity Crotty Jenny Bussell Phil Jarvis Gemma Fox

Figure 1

Earthworm abundance in relation to compaction alleviation methods in 2018 and 2019

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2019