What is Green Manure?

If you are new to growing your own crops, then you may have heard people talk about green manure without having a clue about what it is or what it does? Green Manure may not sound very pleasant but it is a wonderous medium for the health of your soil and subsequent crops.

A green manure is a crop that is grown to benefit the soil rather than to cut or to eat. It is a quick growing seed which can be sown where you have free space in your raised beds or vegetable plot. The green manure crop is then dug into the soil a few months later as rich organic matter full of beneficial soil nutrients. Green manures also help to suppress weed growth in your empty vegetable beds and so are most often used during late Autumn and Wintertime. 

The process of growing a crop solely to benefit the health of the soil and subsequent planting is not a new idea but after World War 2 man-made chemicals were produced that could enhance plant growth, increase productivity, kill pests and diseases and generally replaced the need to look after the soil organically. So much more is now known about the harmful effects of some chemicals on humans and our predatory insects that there is a greater awareness of returning to more natural ways of ensuring the soil and the subsequent crop, is healthy.

Green manuring is an easy, effective and cost efficient method of:

Improving Soil Structure – Some green manures have deep penetrative roots that can open up the soil which is of great benefit on heavy, clay soils as it allows for improved drainage. On lighter soils, green manure once dug in, can help the particles of soil bind together so they can hold water better.

Suppressing Weeds – Green manure crops grow quickly and their very leafy growth smothers weeds. It is a living mulch which suppresses weeds and retains moisture in the soil which is why they are commonly used during times of the year when vegetable beds may be lying fallow.

Adding Nutrients – Some soils need a rest to recover from constant cultivation and by planting with a green manure it will help soil fertility and structure with very little effort. Certain green manures absorb nitrogen from the air and fix it in root nodules on their roots so that when it is dug in it becomes available to the following crop. Nitrogen is important for healthy stem and leaf growth.

Protecting Soil – As a living mulch, a green manure during Wintertime, helps to protect the soil from compaction due to heavy rainfall which often erodes nutrients from the soil.

Green manures are sown and then cut down before flowering so as to prevent seeds growing. The plant material then be dug in and left to decompose but allow 30 days before planting the next crop.

If you are a fan of a no dig system on your plot you simply cut down the green manure crop and leave the foliage on the ground to decompose. This layer is treated as a mulch and planted through or the foliage can also be removed and composted.

It pays to do a bit more research into what individuals green manure crops can add to your soil depending on your own particular needs but for the price of a packet of green manure seeds, you can add rich organic matter full of beneficial soil nutrients to your vegetable plot to help increase soil structure and fertility, in time for planting up again in Springtime.