What used to be known as green manures have taken on a new significance, they are now called cover crops and are used to protect and improve soil.
In many ways the benefits are the same in terms of returning nutrients but there is another crucial effect. Current research has shown how crucial the network of soil fungi are in protecting and improving soils structure and enhancing the nutrient levels available to plants.
The use of mycorrhizae fungi has increased over the last decade. Now there is evidence of the beneficial relationship between the fungi and plants roots. The roots exude sugars which feed the fungi in return the fungi breakdown organic matter into the nutrients the plants need.
The key thing to remember is that the web of hyphae, the thin, white cotton like strands of the fungi are easily broken by digging. In agriculture many farmers in the US are turning to ‘no till’ growing meaning that they do not plough after harvest but sow straight into the ground. The same applies to gardening, stop digging as it destroys soil structure!
The regime here is to remove crops with as little soil disturbance as possible, mulch with compost and sow into the mulch. During winter, the beds are covered with a crop which is cut down in spring, covered with compost and new seeds sown.
(Please note: I have no affiliation with Marshalls other than occasionally buying seeds from them.)