Cover Crops & Game Cover

A cover crop is a non-cash crop grown primarily for the purpose of protecting and improving the soil which can be used repeatedly as part of a long-term farming plan. They can bring agronomic and environmental benefits to the land by adding nitrogen and organic matter to the soil, and research shows that improved soil characteristics and higher yields can be achieved when cover crops are grown in-between periods of regular crop production.

Our varieties are expertly bred by UK and European plant breeders and commercially tested before being brought to market.

Benefits of Cover Crops & Green Manure

Stops soil erosion
Suppresses weeds
Prevents nitrogen leaching
Adds organic matter to the soil
Releases atmospheric nitrogen into the soil (legumes)

Mowing

Most green manure crops should be mown to help with weed control, especially when the cover crop is young. Mowing early can make the difference between a well established cover crop and one full of weeds. Most species can tolerate being cut fairly close to the ground which should help to control the weeds. Exceptions are Sweet & Crimson Clovers which shouldn’t be cut lower than 15-20cm and Vetch which shouldn’t be cut at all. Fortunately, Vetches are very quick to grow so mowing to avoid weed ingress is not an issue as it will compete well with any soil borne weeds.

Cutting not only cuts the top off the weeds but also encourages the cover crop to grow lush green material and delays the crop growing to seed. If not topped, most crops will go stemmy and make them more difficult to incorporate into the soil.

Ideally, it is best to remove the cuttings, especially with legumes as this encourages them to fix more nitrogen. The clippings, if left on the ground will start to rot, releasing nitrogen which will suppress the growing plants to fix more atmospheric nitrogen. If removing the clippings is impractical (which it is in many cases), using a flail mower should help to distribute the cut material more thinly and evenly across the field.

Incorporation

This can be done either by rotavating or ploughing but before doing this, it is best to mow the crop first as this make incorporation much easier.

Sowing the next crop

Be aware that many cover crops, when incorporated have an “allelopathic” effect on the soil which not only prevents germination of any weed seeds but also if sown too soon, the following crop. A period of 6 weeks should be left after incorporation to allow this allelopathic effect to disappear.

Innoculants

Legumes need a Rhizobium bacteria to help the plants fix atmospheric nitrogen. Most species utilize a type of Rhizobium which is readily available in the soil but some species such as Lucerne, Sweet Clover & Sainfoin require a different strain of Rhyzobium which is not readily available so it is always best to sow these species with an inoculant which contains this particular bacteria.The inoculant is normally available as a peat based product, coming in sachets which need to be mixed with the seed just before sowing although some varieties of Lucerne are now available which have been pre-inoculated, being incorporated as a coating which is even easier to sow. Whichever type of inoculant that is used, it is only needed to be done the once at time of sowing and both types are passed by the organic certifying authorities.

Choosing the right Cover Crop

Choosing the right cover crop for your needs is important as different species have different attributes. Some crops are quick-growing for short term covers, others are slower growing but more winter hardy therefore better suited to autumn sowing where the cover is required over winter or even longer.

After being incorporated back into the soil, different crops release the Nitrogen at different rates this means that a cover crop can be matched accurately to the needs of the following crop.

Green Manure & Cover crops

Species	Fixed/Holder	Duration	N Release	Spring/Autumn
Red Clover	Fixer	1-3 Years	Quick	Spring/Autumn*
White Clover	Fixer	2-5 Years	Quick	Spring/Autumn*
Yellow Trefoil	Fixer	6-18 Months	Quick	Spring
Crimson Clover	Fixer	6-9 Months	Quick	Spring
Sweet Clover	Fixer	6-18 Months	Quick	Spring
Vetch	Fixer	6-10 Months	Quick	Spring/Autumn
Lucerne	Fixer	2-4 Years	Quick	Spring/Autumn*
Forage Rye	Holder	6 Months	Slow	Autumn
Mustard	Holder	2-4 Months	Slow	Spring/Autumn*
Buckwheat	Holder	4-6 Months	Moderate	Spring/Summer
Phacelia	Holder	4-6 Months	Slow	Spring/Summer
Italian Ryegrass	Holder	6-12 Months	Slow	Spring/Autumn
Sainfoin	Fixer	2-4 Years	Fast

Green Manure & Cover crops

Lucerne

UK livestock farmer are now showing interest in Lucerne, it has the potential to provide yields of 10-15 tonnes of dry matter per hectare. Lucerne is highly digestible, with high protein, rich in trace minerals and is an excellent source of fibre. With the added advantage being a legume, it will fix nitrogen too.

Typical silage analysis

ME 9.7-11.1MJ/KG/DM
Crude Protein 16-24 %
D-value 70D
PH 4-4.6

These nutritional values will save on farm imported proteins.

It is typically grown as a stand-alone crop, and usually grow for silage, but it can be grazed. With good management practices it will persist for 5-6 years. Modern varieties have been selected for their suitability for the northern European climate and are therefore suitable for the UK. Lucerne will leave considerable residual nitrogen allowing following crops to thrive. Lucerne suits most soil types however, it prefers soils that are well drained, a pH between 6.2 and 8.5 (ideally pH7), and where perennial weeds are not an issue.

Lucerne can be grown successfully with grass as a mixture. During drought periods as we have experienced of late in the UK and due to Lucerne’s drought tolerance, dry matter yields from grass and Lucerne mixtures have been several times higher than grass alone.

To get the best returns from Lucerne:

Select a variety that is suitable for the UK
Time between cuts a minimum of 5 weeks
Optimal cutting height of 7cm
Cut when at the flower buds
Allow to flower once a year to allow nutrients to be stored in the tap root giving winter hardiness and early spring growth.

Sowing Date: From April through the spring. Summer sowing in August and early September will result in heavier crops the following spring.

Sowing Rate: Sowing rate of 8 kilos per acre as a straight stand, or as a mixture 50% Lucerne and 50% Grass up to 70% Lucerne and 30% Grass.

Mustard

Mustard is one of the cheapest cover crops and grows rapidly lifting nitrogen from the soil and holding it until ploughed in. Because of its quick growth it is an excellent weed suppressant. Mustard can be sown any time after late March and will flower after around 6 weeks so is a very short term cover crop. Mustard doesn’t require topping during its growth stage but it is best to top it before incorporating.

Suggested sowing rate 20 kilos/hectare (8 kilos/acre)
Organic seed is normally available

Buckwheat

Not a Nitrogen fixer but a rapidly growing annual crop that will not only lift nitrogen from the soil but will also scavenge for phosphate which is also taken up and released for any subsequent crop on incorporation. Buckwheat produces a large amount of biomass and although it’s large leaves give generally good weed suppression, some of the ground hugging weeds may survive under the canopy.

With a high seeding rate a relatively expensive seed, Buckwheat has a limited appeal for green manure use and tends to be used more in the UK for game cover. The ideal sowing time is April or May when there is no risk of frost.

Suggested sowing rate 70 kilos/hectare (30 kilos per acre)

Crimson Clover

An annual clover, grown to produce a rapid boost in soil fertility. It is especially useful for short breaks in intensive horticulture. Like most clovers, Late March – Early May or Mid – Late August are the best times to sow for a successful establishment.

Suggested sowing rate 15 kilos/ha (6 kilos/acre)

Forage Rye

Although not a legume, because it grows in colder temperatures than most crops, Forage Rye is the ideal crop for holding Nitrogen and reducing leaching over the winter period. It is normally sown on its own or in combination with Vetches to give an excellent winter hardy cover. Because of its cold tolerance, it can be sown later than any other green manure crop, being sown in September or even October. It establishes quickly and gives excellent weed control. Because of the high sowing rate, Rye tends to be one of the more expensive of the cover crops although the later sowing time means that it has the distinct advantage that there is less of a rush to get it in after the previous crop than the majority of other cover crops.

Suggested sowing rate 180 kilos per hectare (75 kilos per acre)
Organic seed is sometimes available

Italian Ryegrass

One of the most rapidly growing grasses, Italian Ryegrass can be sown as a pure stand or with Red Clover or Vetches. It will go over 1 or 2 winters and has a certain amount of frost tolerance although topping prior to the winter is always an advantage. It will produce large amounts of green material but needs topping regularly during the growing season to prevent it going stemmy and producing seed heads. Italian Ryegrass can be sown from Late March to Late April or August to Late September.

Suggested sowing rate 35 kilos/hectare (14 kilos/acre)
Organic seed is normally available