Choosing the right Green Manure                          

Choosing Green Manure Seeds can seem very confusing but with a little time and using a few rules the options will become clearer.

The choice of seed will depend on why you are planting a Green Manure, how long you require the ground to be covered, what was there before, and what you want to plant after, the time of year and the type of soil you have.

Use the table below when Choosing Green Manure Seeds to help work out which one will be best for you.

VARIETY

SOW DATE

PLANT FAMILY

GROWING PERIOD

SOIL TYPE

NITROGEN

BENEFITS

Alfalfa

Apr -Jul

Legume

2-3 months or up to 1 year for overwintering

Avoid acid or wet soils, likes dry soil best

FIX

Excellent nitrogen fixer, deep rooting draw up sub-surface minerals & break up soil pans, can be turned in the autumn or left to overwinter. It is almost a complete natural fertiliser.

Buckwheat

May – Aug

Polygonaceae*

2-3 months

Tolerates poor soils but does not like heavy soils.

 

Short term, quick growing summer variety, which produces a dense canopy of foliage that smothers, & out competes weeds. Great at scavenging for Phosphate.

Caliente Mustard

March – Mid Oct

Brassica

2-5 months

Most

LIFT

Biofumigant properties (suppression of soil borne pests & diseases by the release of naturally occurring gases).

Crimson Clover

Apr – Sep

Legume

3-18 months

Good loam or sandy soil

FIX

Good choice for smothering weeds, fixing nitrogen from the air and is a fast growing bulky green manure.

Fenugreek

Mar – Aug

Legume

2-3 months

Well drained but slightly heavy soils, will tolerate lighter ones if fairly moist

FIX

 

Quick growing annual, produces lots of organic matter.

Field Beans

Sep – Nov

Legume

Overwinter

Most but especially heavy clay soils. It will not tolerate drought conditions.

FIX

Particularly good on heavy soils as it’s roots penetrate & break up the soil. A nitrogen fixer.

Fodder Radish

May – Aug

Brassica

2-6 months, may overwinter

All types

Holds Nitrogen in the soil

Long tap roots penetrate deep into soil and draw up nutrients. Produces lots of foliage which helps improve soil structure/moisture holding capacity & fertility.

Forage Pea

Sep – Nov

Legume

3-6 months

Most

FIX

Good nitrogen fixer, nutrient leaching prevention overwinter.

Forage Rye

Aug – Nov

Poaceae*

3-6 months

Excellent for clay soil but suits most types

LIFT

Excellent for overwintering, and covering soil. The best option to reduce leaching over winter

General Mix

May – Jul

Legume / Brassica Mix

2-6 months

Most

 

Good all-rounder for all year.

Italian Ryegrass

Mar – Oct

Poaceae*

2-24 months

Most

LIFT

Particularly good at lifting the nitrates in the soil and releasing them slowly. Easy to dig in after winter and fits into any bed in a crop rotation plan.

Lupins

Mar – Jul

Legume

2-4 months

Light sandy acid soils

FIX

Very long tap roots that help break up the soil, excellent nitrogen fixer.

Mustard

Mar – Sep

Brassica

1-2 months

Most

LIFT

Large volumes of organic matter helps improve soil texture & water retention.

Phacelia

Mar – Sep

Hydrophyllaceae*

1-3 months, may overwinter

Most, but particularly dry ones

Holds Nitrogen in the soil

Quick growing, weed supressing foliage, lots of organic matter. Good at attracting bees, hoverflies and wasps

Red Clover

Apr – Aug

Legume

3-18 months

Good loam or sandy soil

FIX

Fast growing perennial excellent nitrogen fixer & bulky growth smothers weeds.

Spring Mix

Mar – May

Legume

2-4 months

Most

 

Good all-rounder for early sowing.

Sweet Clover

Mar to May & Aug to Sep

Legume

Up to 2 years

Most. Does well on hard compacted soils, waterlogged soils, drought resistant & tolerates poor soil

FIX

Has a vigorous root system that draws up minerals & penetrates heavy soil. Produces lots of leafy foliage that adds good organic matter when dug into the soil.

White Clover

Mar – Aug

Legume

6 months or 2-5 years

Most especially silt loam & clay soils but can be tolerant of poor drainage

FIX

Excellent long-term green manure, low growing variety that can be inter-sown in between soft fruit e.g. Blackcurrants, a living mulch.

Winter Mix

Aug – Sep

Poaceae* & legume

3-6 months

Most

 

 

 

 

 

 

 

 

 

 

 

Good all-rounder for overwintering, with good weed suppression and prevents nutrient leaching. The combination of the Westerwolds Ryegrass means any Nitrogen present and stored by the Winter Vetches will be released at a slower rate as the organic matter decomposes over the course of the season.

Winter Tares (Vetches)

Mar – May or Jul – Sep for overwintering

Legume

2-3 months

Avoid acid or dry soils, Likes heavier soils

FIX

Good nitrogen fixer, weed suppression, nutrient leaching prevention overwinter.

Yellow Trefoil

Mar – Aug

Legume

3 months up to 1 year

Copes with light dry soils, preferably not acid

FIX

Low growing so suitable for intersowing between taller crops with open canopies like sweetcorn or beans etc. Good at fixing nitrogen, and good at suppressing weeds.

 

*Doesn’t affect crop rotation.