Green and brown manure
Growing a green manure crop is recommended as a way to keep your soil covered in winter (nature abhors a vacuum). Digging it in improves the structure of the soil and gives the nitrogen used in growing the crop back into the soil before the growing season. There is a choice of green manure crops, such as mustard, clovers, vetch (from the bean family) and rye grass (dangerous!).
In 2013 I grew it for the first time but the only green manure seed I could find in early November was mustard. A disadvantage of growing mustard is that it is a member of the brassica family, so you use up the cabbage slot in the rotation. It grew a bit too strong for my taste, with long thick stalks. The leaves can be eaten, but I’m not a fan. I ended up cutting the stalks in early spring and putting them in the compost and then using another batch of compost from home to put on the plot. (Here’s a photo of mustard growing in another plot this year.)
In 2014 I made sure to get my first choice of green manure early in the year, a phacelia and winter vetch mix from the Organic Centre in Rossinver. (250g for €4, loads of seeds!).
I already knew phacelia as a pretty, blue flowering ground cover loved by bees before I learned of its usefulness as green manure. It has attractive feathery green leaves, which after sowing in October resulted in a nice green cover by Christmas. The winter vetch is a member of the bean family, so double nitrogen. Unfortunately not much of the vetch came up for me, it may have been a bit slower to germinate, but I suspect birds and the mice helped themselves.
I dug some of the phacelia in during the Christmas holidays to plant onion sets and garlic. It is recommended to leave it alone for a few weeks, but I wanted the garlic in before the frost and the onion sets were not getting any better sitting around. In mid February the garlic is coming up fine, the onions are a bit slower, but I had planted them nice and deep against bird damage.
Don’t try this at home:
On 21 February 2015 I dug in some more of the phacelia and covered that and the rest with newspaper and cardboard (to add carbon) and then I spread a thin layer of shop bought farmyard manure mixed with a small amount of very mature cow dung (very mature, not a bit of a smell, lovely stuff, thank you John B.!) over it. I hope it won’t make too rich an addition, but I felt the soil had become a bit hungry and ‘scratchy’ last summer and could do with extra nutrition and bulk. Just for the hell of it I layered in some ripped up excess leaves of the artichoke to add more fibrous material.
Reading it up on the intranet (of course afterwards) mixing brown and green manure can have consequences to do with surplus nitrogen and I won’t be making a habit of it. We are still a few months away from planting or sowing, quantities are small and I’m counting on exposure to the air on top and the work of the worms at the bottom to give the result I’m aiming for.
22 February 2015