Brassica cover crops

Brassica crops are increasingly used to provide winter or rotational cover in vegetable and speciality crop production. They are also used as fodder for grazing livestock.

Benefits and considerations

There is a good understanding of brassica agronomy
Establishment systems tend to fit with farm equipment
They are often late summer-sown or early autumn-sown (similar timings to oilseed rape)
Field conditions and variety should guide specific sowing dates
There are many types and growth habits
Autumn-sown brassicas can provide good ground cover and deep rooting, helping to mitigate leaching risks and improve soil structure
Good autumn establishment is critical to maximise growth, particularly where soil structure or nitrogen capture are key objectives
Some brassicas have trap crop and biofumigant activity, suppressing soil pests – especially root pathogens and plant-parasitic nematodes
Consider potential rotational conflicts, such as clubroot pressures, where vegetable brassicas or oilseed rape are grown

Brassica cover crop examples

Suitable brassicas for cover crops and green manure include mustards, oil radish, tillage radish, stubble turnip and kale.

Mustards: Mustards are fast-growing. White mustard develops an extensive root system but is not frost tolerant. Brown mustard produces a good root system and is frost tolerant. It can also be used to suppress verticillium, rhizoctonia and potato cyst nematodes (PCN).

Sowing (autumn): Mid-Aug to mid-Sep
Example sowing rates kg/ha (as a single species): 5–15

Oil radish (oilseed radish): This crop has fast growth in late summer and autumn and allows a significant uptake of nutrients. It develops a large taproot that can break through compacted layers, allowing deeper rooting by the next crop. Oil radish dies over the winter and decomposes by spring. It leaves the soil in easily crumbled condition and improves rainfall infiltration and retention. It also eases root penetration and development by the following crop.

Sowing (autumn): Mid-Aug to early-Sep
Example sowing rates kg/ha (as a single species): 4–12

Oilseed rape: Oilseed rape can provide a competitive cover.
• Sowing (autumn): Mid-Aug to mid-Sep
• Example sowing rates kg/ha (as a single species): 5–15

Note: Example sowing dates and rates (where shown) are taken from the AHDB cover crop review.

Further information

Grazed brassica and forage crops for cattle and sheep

Back to: Types of cover crops

Topics:

Cover Crops Soils Water

Sectors:

Beef & Lamb Cereals & Oilseeds Dairy

Tags:

cover crops catch crop green manure