What to Grow for a Cover crop or Green Manure Crop (Part Two)

Cover crops and green manure crops are a vital part of any good soil management programme, they are a fantastic way to get your soil in tip top condition while resting it and by not leaving it bare or letting it go to weed, the micro life of the soil remains intact and the essential work under the surface continues.

The simple difference between a green manure and a cover crop, is cover crops are grown over a longer period than green manure crops and so take longer to decompose as they will produce ‘woodier’ stems.

• So, what do you grow and when?
• What crops fix nitrogen and which don’t?
• How long do different crops take to ‘mature’ before slashing?
• Which crops do I sow in the summer and which in the winter?

The following is a list of different crops, when to sow, how long to grow them before slashing and if they will fix nitrogen or not…

A quick overview of green manure and cover crops.
Cereal Rye Crops: Barley, wheat, oats, millet, sorghum, buckwheat. All these crops are general soil improvers and DONT fix the nitrogen in the soil.
Legume Crops: Chick pea, field pea, cowpea, pigeon pea, lablab, navy beans, adzuki beans, soy beans, lentils, alfalfa/lucerne, lupins, red, white and strawberry clovers. All these crops have the ability to take the nitrogen from the air into the soil and store it in nodules on their root systems and with the assistance of a friendly bacteria called ‘rhizobium’ they can then make it into a form that other roots can use.

Legume Crops that ‘fix’ nitrogen in your soil:
Alfalfa/Lucerne (Medicago Salvia)
Good Green Manure Crop
Nitrogen Fixer
A deep rooted, tall growing, perennial legume, which like a lot of room and time to grow for a whole season. Provides plenty of green organic matter for your soil and being deep rooted also brings up the minerals that are found deep within the soil to become available for your next crop.
How much to Sow: 15g/1/2oz per square metre.
When to Sow: Sow in summer and slash in spring or sow in spring and slash in autumn

Adzuki Bean (Vigna angularis)
Good Cover Crop
Nitrogen Fixer
Annual vine which has been grown since before 1000BC, native to the Himalayas it’s extensively grown through out Asia, especially China and Japan. Adzuki bean pods are relatively small for a bean, growing to 5mm but they are prolific producers, this is why I like to grow this particular crop as a cover crop because then I can harvest the delicious beans before slashing the vines. I love this dual cropping idea!!
How much to Sow: Broadcast or single sow the a depth of 2cm.
When to Sow: Early spring to early autumn

Broad Bean/ Fava Bean (Vicia faba)
Good Green Manure Crop
Nitrogen Fixer
A sturdy hardy crop which will survive the winter almost anywhere. It is THE best nitrogen fixer and can be used to grow a crop of wonderful young broad beans before you slash the crop for composting.
How much to Sow: Broadcast seeds and cover with 5cm of soil.
When to Sow: In autumn and early summer and slash when pods have just set or leave until after bean have been harvested.

Chick Pea (Cicer arietinum)
(also know as garbanzo bean, Indian pea, ceci bean, Bengal gram)
Good Cover Crop
Nitrogen Fixer
Chick peas were the earliest cultivated vegetables with 7,500-year-old remains found in the Middle East. I grow crops that are a valuable harvest as cover crops, this is a good way of utilising the land, both replenishing it and providing food.
How much to Sow: Broad cast seeds evenly and cover with 5cm of soil.
When to Sow: Early spring to early summer

Cow Pea (Vigna unguiculata)
(Other names include crowder pea, black-eyed pea and southern pea)
Good Cover Crop
Nitrogen Fixer
Cowpea is one of the most ancient crops known, mainly grown for its leafy greens, green pods, fresh shelled green peas, and shelled dried peas. Another useful dual cropper, compact and delicate grows to a height of 30 to 36 inches seed pod is typically 3 to 6 inches long and has 6 to 13 seeds per pod.
How much to Sow: 50 pounds per acre
When to Sow: Spring to summer 1 to 1 1/2 inches deep

Field Pea (Pisum sativum)
Good Cover Crop
Nitrogen Fixer
Field pea is an annual, cool-season, pulse (legume) crop There are has two main varieties of field pea. One type is an aggressive climbing variety and the other is a bush or dwarf type.
Field pea stems can grow 2 to 4 feet in length. stems (or vines) are prostrate at maturity. The pods contain from four to nine seeds and may be up to 3 inches in length Young field pea plants are extremely tolerant to frost. If the main sprout is killed by frost, another shoot will emerge from below the soil surface.
How much to Sow: Sow 1 to 2.5 inches deep in 6- to 7-inch rows.
When to Sow: Cool season cultivar, sow in early autumn for spring slashing

Lupins (Lupinus perennis)
The lupin family has between 200 and 600 different varieties, and they make good companion plants for crops that need significant amounts of nitrogen vegetables like cucumbers, squash, broccoli, and spinach.
The yellow seeds called lupin beans, were popular with the Romans, who spread the plant’s cultivation throughout the Roman Empire which accounts for some of the names like ‘lupini’. Did you know, Lupin beans are commonly sold in a salty solution in jars (like olives and pickles) and can be eaten with or without the skin.
How much to Sow: Broadcast seed thinly between crops then rake over some soil.
When to Sow: From spring onwards.

Navy Beans (Phaseolus vulgaris)
(also called pea bean or haricot)
Good Green Manure or Cover Crop
Nitrogen Fixer
More commonly a herbaceous annual plant domesticated independently in ancient Mesoamerica and the Andes, and now grown worldwide for its edible bean, popular both dry and as a green bean. The leaf is occasionally used as a leaf vegetable, and the straw is used as animal feed.
How much to Sow: Broadcast seed evenly over a large area or single sow seeds to a depth of 5cm
When to Sow: From early spring to early autumn

Red Clover (Trifolium pratense), White Clover (Trifolium repens) And Strawberry Clover (Trifolium resupinatum)
Fantastic Cover Crops
Nitrogen Fixer
A low growing crop which has an extensive root system that makes it spread far and wide, this could be a problem is left unchecked as it will wander far and wide. This extensive root system is what makes it so good for the organic matter it generates as well as the soft green foliage filled with nutrients.

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