I am digging quite seriously at the moment. I am going down about four spits and burying a mixture of not very decomposed compost; lawn mowings; laurel Prunus laurocerasus shreddings; damson and oak tree branches and weeds. I am not putting this mixture into the soil to increase the fertility but to improve the drainage while giving the ground a sponge to soak up excess water. In the summer when the ground gets a little dry it may release water into the soil by diffusion allowing plants to access it.
Since the allotment has now got onion white rot and club root where I put the compost from the giant compost heap, I am more than reluctant to have any weeds or compost except my own. However, Beryl's allotment had a lot of weeds that needed dealing with so I decided to bury them on my own allotment. I buried them deep though.
There is a lot of hearsay evidence on the internet that Hugelkultur produces good results when brushwood is added to the soil. I like to bury high carbon organic matter quite deep in the soil.
About two years ago, I buried big x Cupressocyparis leylandii branches deep in the soil and reported that I could no longer find them. However, this week I have found some of them when digging in the compost. They are deeper down than I remember and are being decomposed by fungi growing on them even at this depth.
I put quite a lot of inoculated charcoal into this bed for the potatoes and I had to be very careful to keep the various parts of the soil separate to maintain the charcoal in the top layer.
Lots of old woody compost was mixed into the second spit soil. Some quite large branches were being dug up and they looked unsuitable for mixing into the top soil. However, after examining them closely they could be crumbled into quite fine material that mixed into the soil well.
I have dug over about a quarter of the bed at the moment and I have already started to run out of material to bury. I think that I will be lopping off some more branches from the hedge soon.
I hope to plant this area with leaves (chard, rocket, American land cress and lamb's lettuce) together with green manures. The green manures I will be using are crimson clover Trifolium incarnatum, grazing rye Secale cereale and winter tares Vicia sativa leucosperma. These green manures will be dug in in the spring. Only grazing rye will not be a nitrogen fixing plant so I am hoping that digging them in will provide the soil with additional nitrogen.
I am going to sow the green manures in rows rather than broadcast. I have grown green manures like Caliante mustard Brassicae juncea by broadcast sowing in the past and this has been quite successful. Until the green manure has developed a canopy over the ground there is a risk of weeds being able to germinate. They may well be shaded out by mustard but it is best that there is some easy way of weeding. With this in mind, I am growing in rows to facilitate hoeing. Also, I get as good a ground cover in rows as I do broadcast sowing. There are several reasons for wanting a good ground cover. Green manure will prevent winter rains leaching out nutrients from the top soil. It provides a good habitat for micro and macro organisms. It also provides an effective store of nutrients that can be dug into the soil during the spring.