A Complete Guide to Green Manure

A Complete Guide to Green Manure

There has been a major drive over recent years to be more green thinking when it comes to the environment.

Even manure has gone green.

Remember the days when you’d ask the local farmer or stables for a bit of horse muck to throw over your garden to help grow flowers and plants?

Well even that has got more scientific, and in recent years there has been much more research into the science behind soil health, biodiversity and nitrogen fixing and how we can play a part in that from our own humble back gardens.

One of the more favoured techniques now for doing this is incorporating green manure into our horticultural routine.

In this guide we will look at how green manure works, when it is best to sow it and the best ways to dig it in and grow it.

 

What Is Green Manure?

Green manure is the term used for the sowing of fast-growing plants which are used to cover bare soil, with the ultimate aim of improving soil health and putting nutrients into the ground.

It is a technique that can be used on any land parcel size - whether you have corner vegetable plot, an allotment or a big domestic garden - it is well worth looking at the advantages of using green manure on your soil.

One of the most common reasons for opting for a green manure, other than aiding soil health, is suppressing weeds and helping to prevent soil erosion.

Other known benefits to the practice are encouraging soil activity by bacteria, increasing nitrogen, preventing soil compaction, creating a better habitat for wildlife, in particular frogs who can keep slug and snail numbers down, and combating pests.

A number of plants can be used for the purposes of green manure, and a mixture of species is also to be recommended, but a good starting point would be to look at the likes of lucerne, buckwheat, field and broad beans, red and crimson clovers, mustard, rye, vetch, trefoil and phacelia.

How Does Green Manure work?

In order for plants to grow well, in a nutshell, they need nutrients - namely nitrogen, phosphorus and potassium, magnesium, calcium and sulphur.

Meanwhile, healthy soil contains invertebrates, bacteria and fungi, which, when working together, break down organic matter, like manure, and make these nutrients available to plant roots.

Therefore, gardeners and landowners are helping this process by incorporating green manure into their routine, because when that green manure is dug back into the soil and decomposes, it releases the nutrients which were being held by the green manure plant they had selected, back into the soil.

 

When to Sow Green Manure?

The best time to sow green manure is perhaps dependent upon the main purpose you have for doing it, but a rule of thumb is that green manure seeds are best sown from spring through to autumn.

If your main need for a green manure is to prevent soil erosion, then sow the green manure plant around late summer or autumn with a view to digging them back in for the next year’s spring.

On the other hand, you can have a much quicker turn-around with green manure if you are looking to have a cover of bare patches of soil in the intervals between growing something else. In that instance you can look to dig them back in from a month to six weeks after sowing.

If you are looking to suppress weeds, then summer-grown green manures are considered best for this purpose, while green manures that can help fix nitrogen do this in summer so they will need to have been sown between April and July.

 

How to Dig in Green Manure?

The recommended time to dig in green manure is three or four weeks before you want to use that land for growing crops, and a good month or so before if you are using the land for sowing seeds. This gives the manure time to rot down, decompose and transfer the nutrition back to the soil.

However, if the green manure looks like it's approaching maturity, dig it in sooner than this. Younger, green growth decomposes and feeds the soil within weeks, but older plants can take longer.

You can tell if they are reaching their full maturity because they may start producing flowers and buds. The upside to this is that they can attract bees and pollinators, the downside is that weeds can start to creep in.

When it comes to actually digging in the plant, a good starting point is to cut the foliage down first. Then, let it wilt for a couple of days, before using a sharp spade to turn over the roots and then dig them back into the soil along with the rest of the greenery.

Green manures that are young can be dealt with by being sliced off with a hoe and the foliage and greenery being allowed to rot back into the soil.

An alternative approach, if you don’t want to dig the soil, is to just take the height of the green manure crop right down with a strimmer and cover the planted area with plastic sheeting for a month which will also encourage the green manure to decompose.

 

How to Grow Green Manure?

It is fairly easy to get green manure into your ground and established once you have worked out which particular one you are going to use to meet your particular need and over what size land parcel.

Prepare the soil by digging it over, taking out any weeds and breaking up heavy clumps before raking it over to create a fine textured substance. Tread the soil and then scatter the seeds in an even consistency across the soil. This helps to make sure that there is a good enough cover to keep weeds down.

If you are using larger seeds, these can be distributed in even rows and once you have got the seeds are in, rake the soil back over the top and water the whole area well.

Depending on the weather conditions, say it is hot and dry, make sure the soil is kept moist by watering, but of course, should there have been a decent amount of rainfall, this will reduce some of the work-load for you.

 

What is the Best Green Manure?

There are a number of plants you can choose in order to make a successful green manure so it can be hard to know where to start.

Legumes, however, are a popular choice and can perform a number of functions in the ground.

Winter vetch is a hardy choice and will perform well over winter even in heavy soils. Another good option to use in heavy soils are winter field beans, and grazing rye also, as both can help improve soil structure as well as being able to withstand winter.

Plants from the clover family are plentiful but two good ones to consider are red clover and crimson clover. The former works well in loamy soils and can be left in the ground for anything between two months or two years, while the latter will be best dug in after a few months but does help lighter soil types.

If you only require the crop to be in the ground for a few months before you re-plant or seed, then there are some good quick growing options to look out for.

Mustard can be dug in within three months of sowing, buckwheat is good for soil that is lacking in nutrients, bristle oats can be dug in after a couple of months and bitter blue lupin is a good option to counteract light, sandy and acidic soil.

However, here at Rural Supplies Ltd, we have a number of ready-made seed mixes that have been specifically created to provide the best green manure solution for your needs.

They include micro-clover, crimson clover, mixed clover, white mustard, red clover, white clover and an autumn/winter green manure mix.

We have also got 100 per cent mixes that will produce green manure. They are birdsfoot trefoil, yellow trefoil and phacelia.

See the full selection available at Rural Supplies here https://ruralsuppliesonline.com/collections/green-manures

 

Summary

Green Manure is becoming a more popular method to aid soil health and prepare your ground for the next stage in planting and growing.

By using crops to improve soil health, keep weeds and pests down and add nutrients to the soil, it is quite a step change from what has been a more widely adopted method of using chemicals and fertilisers on gardens instead.

Green manure works by having a quick growing crop on bare land and when it is at its optimum stage of growth, it is dug back into the soil and passes on all the nutrients it has been storing back into the soil.

Some green manures work better or faster than others, depending on the type of soil you are working with, but a plant within the legumes family is a good base to work with.

Although at first glance it may appear to be a time-consuming task, the use of green manure, as part of your annual gardening and growing plans, is well worth considering as it has significant environmental and financial benefits.