Date of Case Study: 2012

Farm Name: East Hendred Estate

Location: Oxfordshire

Enterprise: Mixed Arable and Sheep

Farm Size: 607 hectares

Sustainable Practices: Controlled traffic farming and considering renewable energy options

Business Benefits: Considerable savings in regular fuel and time costs. In the longer term, improved soil health and reduced inputs/yield increases are expected.

Sustainable Farming Approaches

Farm Manager Julian Gold has adopted Controlled Traffic Farming (CTF) and minimum tillage to reduce emissions, but also as a wise business decision. The technique involves using only the same necessary tracks across fields for land work, planting and harvesting, never driving on the spaces between these tracks. Driving over and deep cultivating fields compacts and disturbs soils, causing Carbon stored in the growing cycle, and crucial nutrients, to be released, depleting the Soil Organic Matter. In total, only 20% of the farm’s field area is driven over. Specialist equipment such as direct drilling and adapted automatic bale collectors are utilised. 

Combining cultivating and drilling using one implement for both has saved over £50,000 in capital costs. Meanwhile the reduced fuel use saves around 10 litres per hectare in a typical crop cultivation sequence. The minimum tillage system improves worm count and water drainage, and improves soil structure, and in conjunction with the robust rotations and stale seedbed techniques helps control problem weeds such as Blackgrass. The relatively large average field size has been advantageous for this approach, to set up a 10 metre CTF approach, and smaller farms could set up smaller (6 or 8 metre) widths to benefit from the same advantages. The management of trash and wheelways as a CTF system progresses over time does need an element of hands-on management and this may mean re-examining equipment in the future. 

The estate has also adopted robust, wide rotations, which include legumes, to reduce nitrogen use and reduce pests and diseases. 

Future Plans: Cover Crops and Renewables

The intention is to bring in cover crops between winter and spring crops – this recycles nutrients, improves soil structure, retains living roots and allows soil biota to thrive, benefitting soil health and resilience. Plans under discussion include examining the numerous coniferous windbreaks on the estate as potential sources for biomass energy supplies in the future. 

A re-roofing project on an agricultural building will provide the opportunity to install solar panels, which they plan to install at the same time as the roofing work – a good example of combining necessary work already planned on the farm with opportunities for low carbon diversification. 

Carbon Footprint

Due to the size of the arable crop under cultivation, nearly 90% of the farm’s emissions are a result of the agro-chemicals used on crops, the majority (83%) coming from fertilisers. Due to the reduced distance driven each year and working wider and shallower in terms of cultivation as a result of CTF techniques, fuel use is lower than would be expected otherwise, accounting for only around 6% of total emissions. 

Livestock emissions are also relatively low at just under 3%, but as the farm has a relatively significant amount of machinery, farm machinery represents nearly half of these emissions (1.4%), with the embodied emissions from materials used on the farm only 0.03%. 

In sequestration terms, there are some good size blocks of woodland around the farm, and together these are removing almost four times the annual emissions of the farm’s livestock from the atmosphere each year. The minimum tillage approach will store carbon in future years, contributing to net sequestration. Regular Soil Organic Matter testing is important for monitoring this.

Summary

As part of a pragmatic overall approach, the Estate seeks to minimise artificial, especially finite fossil fuel-based inputs. Soil is also crucial to the approach as any improvements in soil health will further reduce the inputs required, and improve soil robustness and resilience in both wet and dry years. This focus on soil health is crucial for reducing emissions through lower inputs and sequestering carbon through improved soil health and structure. The farm crucially needs to stay profitable and this approach allows for continued profitability while adopting innovative techniques; the considerable savings alone illustrate the strong economic case. 

Date of Case Study: 2012

Farm Name: Shimpling Park Farm

Location: Bury St Edmunds, Suffolk

Enterprise: Arable (Wheat, Barley, Oats, Spelt and Quinoa) and Sheep

Farm Size: 645 hectares

Soil Type: Chalky Boulder Clay

Key Statistics

Total annual carbon emissions 1,150 tonnes CO₂e Total annual carbon sequestration 454 tonnes CO₂ Total carbon balance (emissions) 696 tonnes CO₂e Emissions per hectare 1.08 tonnes CO₂e Emissions per tonne of product 0.45 tonnes CO₂e. 

Note: CO₂ stands for Carbon Dioxide, CO₂e stands for carbon dioxide equivalence – i.e. other greenhouse gases are included, but converted to a standard unit to  represent the global warming impact of carbon dioxide

Emissions Sources

Total carbon emissions amounted to 1,150 tonnes CO₂e.  

The main sources of emissions came from Fuels (33.5%) – mostly diesel use, and Fertility (54%) –  including nitrous oxide emissions from crop residues and green manures. 

Fuels 

This mostly came from diesel use in tractors and combines (29%). There is also diesel used in  road vehicles for the farm business. This is to be expected in a mechanised arable system. 

Electricity on the farm amounted to 4% of total emission, mostly used for grain drying. It’s also  worth noting that a 50kW array of solar PV panels exports around electricity offsetting 16 tonnes of  CO₂, as well as providing some ‘free’ electricity to the farm. 

Materials 

It’s worth noting that materials used on the farm, including wood, water, metal, paper and tyres  amounted to just 0.1% of total emissions.  

Nonetheless it is worth recording these items because embodied energy in concrete and steel in  particular can have large carbon impacts on large projects – for instance a new barn, shed or farm  roads. 

Capital Items 

As mentioned above, there is a lot of embodied energy in steel, which is exposed in calculating the  impact of farm machinery. In the Farm Carbon Calculator, any machine under 10 years old is  accounted for, and depreciated over 10 years.  

The manufacture of tractors and telehandlers on this farm amount to 3.7% of total emissions.  However if these were all bought in one year and accounted for in one year (not depreciated over  ten) then the impact would be 37% of total emissions.  

Fertility 

Nitrous oxide emissions from crop residues of arable crops (beans, peas, wheat and oats)  contribute to a large percentage of total emissions at 29%. This is due to nitrogen in the crop  residue being oxidised in the soil and being released as nitrous oxide.  

Leguminous green manures (red clover) contribute a further 17% of emissions through nitrous  oxide released during nitrogen fixation. This appears to be a very negative attribute of green  manures, however they can also contribute to a substantial increase in organic matter levels, which  sequesters atmospheric carbon. In effect this at least ‘balances out’ the nitrous oxide emissions. 

Also worth mentioning is the 2.8% of emissions from the application of rock phosphate. 

Livestock 

The farm has a herd of 250 sheep, which contribute 6.6% of emissions from methane through the  process of enteric fermentation (common to all bovines). 

Distribution 

Transport of arable crops to a local mill accounts for 1.3% of emissions. Whilst this is not delivered  to the final customer it demonstrates that ‘food miles’ can be only a small part of the issues relating  to climate change and food. 

Sequestration Sources 

Carbon is sequestered in perennial biomass and soils on farms. On this farm 60% of carbon is  sequestered in woodlands, whilst permanent field margins (21%) and hedges (18%) are the  other main carbon sinks. 

The total carbon sequestered on the farm (454 tonnes of CO₂) offsets 40% of all carbon emitted by  the farm business. 

Note that soil organic matter levels have not been sampled – see discussion below. 

Notes 

The major omission to this calculation, due to lack of data, is that soil organic matter levels have  not been measured. See below for discussion of this issue. A comprehensive calculation of materials used (e.g. wood, steel, concrete, etc.) was not undertaken  due to time limitations. However this was not expected to be a significant source of emissions as a  percentage of total farm emissions. An analysis of embodied energy in farm buildings was not carried out, also due to time limitations.  This would be worth looking at in future calculations, but it is not considered that emissions from  embodied energy in buildings would skew the figures dramatically.  

Discussion 

In organic systems a major aim is to cultivate soils in a manner that builds fertility continuously.  This should go hand in hand with raising organic matter levels, which also means atmospheric  carbon is being sequestered in the soil. 

For example a 0.1% increase in SOM on clay soils, per hectare per year, can sequester nearly 7  tonnes of CO₂. If this applied to the whole of Shimpling Park Farm then the annual carbon  sequestration from soil alone would amount to almost 4500 tonnes of CO₂, four times greater  than total carbon emissions! 

Is this achievable? In the Soil Association paper Soil Carbon and Organic Farming (2009) a  comprehensive analysis of studies is made that examines soil organic matter (SOM) levels in  farming systems across the world. There was a huge range of results in temperate organic arable  systems, from SOM increases of 0.5% per year through to annual SOM losses. However it  confirmed that annual SOM gains of 0.1% are perfectly achievable. 

Even if annual SOM gains were just 0.025% then on this farm the carbon sequestration in soil  would equal all the carbon emissions from the business. Add to this the sequestration from  biomass and the farm would have net carbon sequestration. 

Date of case study: 2012

Farm Name: Tolhurst Organic Produce

Location: Berkshire

Enterprise: Field Scale Vegetables with a Veg Box Business

Farm Size: 8 hectares

Sustainable Practices: Wildlife habitat creation, recycling and green manures

Business Benefits: Improved soils for increased productivity 

Carbon Balance: Positive impact as a results of sequestration activities

Tolhurst Organic Produce

Tolhurst Organic Produce is one of the UK’s longest established organic vegetable growing business. Based on the Hardwick Estate west of Reading in the Thames Valley, they have 7ha of field scale veg and a 1ha walled garden, growing more of the labour-intensive crops. The main income source is a veg box scheme supplying families in Reading and Oxford. Environmental awareness is at the core of the business and Iain ‘Tolly’ Tolhurst is widely regarded amongst peers as being a grower who pushes the boundaries and sets high standards. Tolly has long been interested in supplying vegetables to his customers with a low carbon footprint, and in 2001 commissioned the University of Surrey to examine his business operations from an environmental perspective. Completing the Farm Carbon Calculator in 2012 has been a natural step for the business. 

Carbon Emissions

Farm operations are quite simple, with most diesel used in tractors for cultivation and carting (two thirds) and pumping water for irrigation (one third). This accounts for just under 19% of total emissions. Distribution to customers is done by van to drop-off points in nearby Oxford and Reading, every week of the year. Total emissions, from using the farm’s own van and a local courier, account for 33% of emissions. Box scheme businesses are disadvantaged from other businesses in terms of carbon emissions because they deliver to the customers’ door, whereas for many farms point of sale occurs at the farm gate. 

Electricity is a significant contributor to emissions at just under 17% of total emissions; about half of this is used in propagation for heat-loving crops like tomatoes, cucumbers, peppers, etc. Materials use and emissions (2.5%) is very low, due to a policy of re-use and tight financial controls on consumables. Even packaging for deliveries is reused many times, much reducing resource use. For instance paper delivery bags are re-used 5 or 6 times, reducing use from 1 tonne to 200kg of new bags per year! There has been a conscious decision to decrease the amount of plastic used. Embodied energy in the business’ van, being less than 10 years old, contributes 6.3% of total emissions. 

The farm has no livestock, using green manures to build fertility in the soil. These green manures, including red, white and crimson clover, vetch and lucerne, account for 11% of total emissions through N₂O they release as part of the Nitrogen-fixing process. However this pays handsome dividends in both Nitrogen and Soil Organic Matter (see later). Tolly also uses woodchip derived, locally sourced organic compost, which improves Soil Organic Matter. Waste management is taken very seriously and all waste is recycled. This gives an emissions offset equivalent to 10% of total emissions.

Sequestration

A policy of creating habitat for wildlife in the fields also has given opportunities for a lot of carbon sequestration. Hedgerows are allowed to grow tall and wide, accounting for 17% of total sequestration. A small area of woodland, along with an area of willow coppice in a damp corner of one of the fields, account for over 24% of all sequestration. 

One of the most surprising figures perhaps was for the amount sequestrated in the field margins. This permanent pasture around fields and beetle banks within fields is actually quite a large area, nearly 1 hectare in total, and accounts for nearly 9% of total sequestration. 

The biggest challenge for growers is how to build Soil Organic Matter, because cultivating soil is the best way to lose it! Over the course of the last 25 years, Tolly has managed to continually build organic matter levels without the use of external inputs. This has been achieved through extensive use of green manures and a tillage policy of shallow and timely cultivations. This is a remarkable feat, and the positive contribution of rising organic matter levels across cropped areas accounts for an impressive 49% of all sequestration.

The Overall Balance

Total emissions come to 16.6 tonnes of CO₂e (a measure of all greenhouse gases expressed as the equivalent in CO₂) per year, a remarkably low figure for a business producing veg for 150 families. But most excitingly, total sequestration comes to around 21 tonnes of CO₂e per year, meaning the whole farm is ‘carbon positive’ by over 4t CO₂e per year. This shows that there are methods of growing vegetables with minimal inputs, producing good yields and still sequestering far more carbon than is emitted. 

Summary

All Tolhurst Organic Produce customers receive vegetables every week that technically lowers their carbon footprint. This is an exciting concept and demonstrates the power of farmland to turn agriculture and horticulture into a carbon positive activity that can help to bring down atmospheric CO₂ levels and reduce the impacts of climate change.