Using Green Manures
Phacelia in flower
A green manure is a cover crop, grown specifically to improve soil fertility. This living mulch will also help to suppress weeds, provide cover for predatory creatures such as frogs and beetles and protect the soil from harsh weather.
There are different crops suitable for growing at different times of year: Some will overwinter and hold on to nutrients that might other wise be washed away by rain - the nitrogen lifters. These are especially useful on the thin chalky soils around Brighton.
Some are fast growing and could be sown in the summer where there is a gap in your rotation eg fenugreek and phacelia.
Many of them belong to the legume family and are able to harvest atmospheric nitrogen which later becomes available to other plants.
Normally, green manure crops are dug in and allowed to rot down into the soil about a month before sowing the next crop.
Some of the plants - buckwheat, clovers and phacelia - can be left to flower and will provide nectar for pollinating insects.
Tip: empty your old seed packets of unwanted seed. Mix them all up together and sow these as a green manure.
| Sowing time | Crop | Nitrogen fixer or lifter? | Does it over winter? | Where does it fit in a rotation plan? |
| March – June | Lupin | Fixer | No | Legume |
| March – August | Fenugreek | Fixer | No | Legume |
| March – August | Trefoil | Fixer | Yes | Legume |
| March - September | Mustard | Lifter | No | Brassica |
| March – September | Phacelia | Lifter | It might do | Anywhere |
| March - September | Tares | Fixer | Yes | Legume |
| April – August | Buckwheat | Lifter | No | anywhere |
| April - August | Other clovers | Fixer | Yes | Legume |
| April - September | Crimson clover | Fixer | It might do | Legume |
| August - September | Radish | Lifter | No | Brassica |
| August - September | Grazing Rye | Lifter | Yes | anywhere |
| Spring or Autumn | Annual Rye | Lifter | Yes | anywhere |
| September- November | Field bean | Fixer | Yes | Legume |