No dig gardening benefits soil, but beware of pitfalls expert warns

A minimum cultivation approach to growing vegetables is enriching the soil and controlling weeds at a Welsh market garden, but a horticulture expert warns of some potential pitfalls to consider when embarking on no dig gardening.

William Roberts is in his fourth season of growing vegetables on a commercial scale at five-acre Cae Newydd, Upper Brynamman, on the edge of the Black Mountain.

He recently hosted a Farming Connect open day to share his experiences with others interested in no dig gardening.

He explained that he had established the first section of his vegetable beds by placing a cardboard barrier on 30-inch wide beds, topped with horse manure and with woodchip in between rows.

The second set of beds were established in a similar manner but using green waste compost. Soil spear samples showed that the depth of dark organic matter rich soil was directly related to the length of time the beds had been established. Below this, the soil was clay with rust flecks, indicating gleying and compaction, exacerbated by the heavy rainfall on the south slope of the Black Mountain and at an altitude of 270 metres.

More recently, green manure cover crops are being used in the newer beds to increase organic matter content more rapidly.

By adding these layers of nitrogen and carbon-rich materials – a thick layer initially and topped up with thinner layers in subsequent years – Mr Roberts is producing vegetables without the need to apply pesticides.

The only input used is pelleted poultry manure when the soil needs an extra boost.

If managed well, no dig also results in a huge reduction in weeding time, said Mr Roberts.

Crops that are not harvested are left in place as cover to support the soil biology; ahead of planting they are covered with tarpaulin to prepare the beds and this is gradually removed.

While minimum cultivation gardening has been shown to be good for the soil and the environment, ADAS horticulture specialist Chris Creed says there are a number of considerations that growers who are considering converting to this system should be aware of.

Importantly, for those who are planning to grow crops commercially, it can take up to two years for the biological action in the soil to settle and that would mean reduced yields in that period. “It is quite a process to work through,” advised Mr Creed, a speaker at the Farming Connect event.

He recommends that the grower composts bought-in manure, instead of relying on this process having been done, to rid it of weed seeds; he suggests creating 1.5m high windrows that are turned weekly to aerate and mix the contents generating high temperatures.

Be aware too that residues from pesticide used for clearing ragwort may be present in some manure if it has been applied in fields where animals supplying it have grazed.

This is especially detrimental for beans, peas and potatoes – it can remain in the soil for two years or more once it is introduced.

To check that manure is safe to use, Mr Creed suggests creating a bio assay – sowing a susceptible crop such as beans to see what happens. 

“If the stem comes up like a corkscrew, don’t use the manure,” he says.

Testing the nutrient status of the soil is important too – if the phosphate index is 3 or above, Mr Creed says phosphate shouldn’t be applied.

While leaving crop debris as a cover is good for the soil, he warns that not all vegetables are suitable for this.

“Be careful that the crop doesn’t go to seed because you can end up with a whole host of new weeds.”

For growers who are interested in no dig gardening, Mr Roberts has a top tip. “My best advice is to spend some time working for someone who has done this, it isn’t straightforward but, if you get it right, it is a very rewarding way to grow food.”

Delana Davies, Knowledge Exchange Executive at Farming Connect, who organised the event, also recommends making use of the Farming Connect mentoring service for input from established growers.

Farming Connect is delivered by Menter a Busnes and Lantra Wales and funded by the Welsh Government and the European Agricultural Fund for Rural Development.