Square Farm, Mitchel Troy, Monmouth

Focus Site Project: Exploring the use of wood chip mulch for weed control in organic vegetable production


Square Farm is a family-run business established in 1978 focusing strongly on traditional farming methods. The business incorporates a flourishing farm shop selling home-grown, organically produced foods as well as an expanding range of selected local produce from the Wye Valley and surrounding areas.

Square Farm operates as a traditional mixed farm incorporating cattle, sheep, pigs, chickens, ducks, and geese. Cereal and root crops are grown for animal feed and an increasing number of vegetable crops are produced to stock the farm shop. The shop also sells home traditionally reared beef, lamb, and pork alongside the very popular eggs from a flock of 200 unrestricted, free-ranging poultry.

Square Farm is proud to be an organic farm. Land management policies have been devised, incorporating the successful Glastir land management scheme at entry level and advanced level, with plans in place to further increase the diversity and habitat management for wildlife. In recent years more than 400 metres of new hedgerows, consisting of British native plants, have been created, while three small orchards have also been established using traditional fruit trees. 

Vegetables are grown to supply a delivered box vegetable scheme including fresh kale, purple sprouting broccoli, carrots, leeks and potatoes. A new venture is the planting of asparagus to be grown organically and supported by a successful EIP bid. The farm is also a member of an EIP group evaluating the use of a computerised robotic weeding machine.


Project aim:

The aim of the project is to assess whether the use of waste wood chip from local tree surgeons can be used to suppress weed growth in organically planted vegetables.

Unlike uniformly textured sawdust and bark mulches, arborist wood chips include bark, wood, and often leaves. The chemical and physical diversity of these materials resists the compaction often found in sawdust and bark mulches, and may promote better performance in terms of moisture retention, temperature moderation, weed control, and sustainability. Arborist wood chips are also available free of charge making them an economically practical choice.

Additionally, the materials vary in their size and decomposition rate, creating a more diverse environment that houses a range of microbes, insects and other organisms. A biologically diverse soil community is more resistant to environmental disturbance and will in turn support a diverse and healthy plant population. Wood chips are considered to be slow decomposers, as their tissues are rich in lignin, suberin, tannins, and other complex natural compounds. Thus, wood chips supply nutrients slowly to the system; at the same time they absorb significant amounts of water that is slowly released to the soil. Wood chips have been cited as superior mulches for enhanced plant productivity.

The mechanism(s) by which wood chips prevent weed growth are not fully understood, but likely includes light reduction (preventing germination of some seeds and reducing photosynthetic ability of buried leaves), allelopathy (inhibiting seed germination), and reduced nitrogen levels at the soil-mulch interface (reducing seedling survival). Using locally produced wood chip also improves sustainability, and the reuse of waste plant materials as mulches keeps them out of landfill.


What will be done

It is important to begin mulch application before annual weeds are established, so bare soil will be mulched as soon as planting occurs before weed seeds germinate. Mulch will be placed in areas between crops maintaining a distance of 100mm from plants to avoid the danger of creating a dark, moist, low oxygen environment around the plant which could predispose to fungal disease and pest propagation.

Two treatments will be established on crops of leeks and kale:


  1. Wood chip mulch 50-75mm depth
  2. Control – no mulch


Plot lengths will be 3m and replicated 3 times across the growing area.

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