Green manures are increasingly being seen as a key component in any rotation. They are often grown as part of a scheme, but have a wide range of potential benefits. They will provide a big root system that will improve soil structure, organic matter, soil biology and provide ground cover that will help prevent soil erosion at risk periods.

They can have subsequent gains for following crops with previously lost nitrogen being retained by the green manure. There is also the potential for summer sown green manures to have a legume component which will fix additional nitrogen. The improvements in soil structure and organic matter should provide a more robust soil that can deal with dry and wet spells and lead to higher yields.

By not leaving bare soil there is a knock-on benefit for the wider environment with cover offering an important habitat for birds and mammals and the summer flowering species crucial to pollinators.

Care should be taken to select appropriate green manures to suit the given situation with sowing date, soil type, incorporation date and primary goal all considered.

MUSTARD – this is a brassica and requires approximately one hundred days to grow to its maximum which can be more than a metre tall. The tall aerial growth is normally pulverised before incorporation back into the soil.
Sowing rate: 2-3kg/acre

BROWN MUSTARD – a specific type of mustard grown preceding potatoes where potato cyst nematode is known to exist. The brown mustard when ploughed in gives off gases which help to eradicate potato cyst nematode.
Sowing rate: 3-4kg/acre

RED CLOVER – This is a longer term green manure which requires to be sown for the major part of the season before it is incorporated back into the soil. It has however significant benefits over the other green manures. The large tap root helps break up and condition heavier soils and the nitrogen held in the red clover root nodules contributes to the following crop.
Sowing rate: 4kg/acre

PHACELIA – requires to be sown in spring once all risk of frost is gone. It produces a large bulk of vegetative growth. It is extremely fast growing and competes well with weed competition. The blue flowers are of huge benefit to insect life producing lots of pollen and nectar. This insect life in turn benefits other wildlife higher up the food chain such as song birds and game birds. A field of phacelia in full flower adds enormous aesthetic value to any farm.
Seed rate: 4kgs/acre

TILLAGE RADISH – This is a relatively new crop. It is a brassica and requires approximately one hundred days to grow to its full potential. It is ideal for growing in late summer after a cereal crop. The elongated bulbs at the base of the plant are of prime importance as they penetrate deep into the soil to help open up heavy soils which may be prone to compaction.
Seed rate: 2.5-3kg/acre

VETCH – It is a legume and part of the pea family. If sown early enough it will fix nitrogen throughout the warmer months. It is relatively winter hardy so a valuable option to be sown after harvest to provide some winter cover. It is fast to establish and is effective at smothering weed competition.
Seed rate: 20-25kg/acre

BUCKWHEAT – It is an extremely fast growing non leguminous annual that should be sown in the spring after any risk of frost. It is not winter hardy and will be easily killed by any frost. It provides a fast growing weed suppression cover that is easy to incorporate.
Seed rate: 20kg/acre