Sanctuary Garden Diary

Composting alternative techniques workshop run by Richard Main.
Richard outlined 3 alternative systems to the traditional compost heap that Judy showed us. These included;

• Crop residue management - 'chop, drop and dig'.
• trenching and
• sheet mulching - a no-tillage method.

Crop residue management 
Green material (nitrogen sources) and brown material (carbon sources) in the garden are processed by cutting, chopping and digging in the plant material. This system has been practised for thousands of years and is still used today.

There are several benefits including;

• organic matter is recycled into the soil
• no cost - easy to implement although it does require effort...
• all that is required is a spade - no reliance on fossil fuels
• is an ideal technique to include as part of a four-block crop rotation
• increases soil biological activity
• 'waste' material is used in the garden
• more efficient than transferring to and then from a traditional compost heap.
• maximises nutrient and energy availability to support soil and plant health
• reduces the need to irrigate due to the high retention of organic matter in the root zone

Crop residue management has been trialled at Lincoln University see http://www.merfield.com/research/2007/has-organics-over-hyped-the-benefits-of-compost.html
Also the September/October issue of Organic NZ, To compost or not to compost Pages 14 - 19

Trenching

Trench composting is very simple. 

Dig a trench approximately 30cm (twelve inches) deep, add roughly 10 - 15cm (four to six inches) of compostable materials, such as kitchen scraps, spent garden plants, prunings, thinnings, weeds -  and bury it with the soil you dug out of the trench.

The next step is.....well, there is no next step.

Trenching makes composting simple.

You don't have to worry about maintaining adequate moisture levels, aerating or turning the way you do with a compost pile. But here are a few more reasons to give trench composting a try:

• It gives plants nutrition right where they need it, at the root zone. Plant roots will make their way down deeper into the soil in search of the nutrition that you have buried there. So the plant will be healthier in two ways: it will be nourished by the organic matter in the trench and it will develop a deeper, stronger root system. This means the plant will be better able to cope with dry conditions and heat.
• It is invisible and will not produce odours. An issue some people have with compost is trying to figure out where to put the compost heap. While there are plenty of small-space composting solutions, trench composting completely eliminates this issue because you can bury waste anywhere you have an open bit of space in your garden. And, because it's buried under several inches of soil, even the smelliest kitchen waste won't be an issue.

Different Ways to Compost in Trenches

You can be as organised or as free-form with your trench composting as you'd like. There are three general methods to use in your garden. All three work very well and work on the premise that you don't want to plant directly on top of composting materials.

• Trench Rotation

This is a method of incorporating organic matter into the garden a bit at a time while maintaining active growing and path areas. The general idea is to divide the garden into three zones:

1. a trench composting zone, 
2. a pathway zone, and 
3. a growing zone. 

Each year, move the trench compost to a different part of the garden and shift the paths and growing areas as needed. By the end of three years, you've got compost under every part of your garden bed and you can start the rotation over again. If you like things very orderly, this is probably the method for you.

• Trenching Between Rows

This works in any vegetable or annual garden in which you would plant in rows. Plant your crops as usual. In the spaces between the rows, dig a trench to toss your compostables into. Fill the trench as you add materials, and it will break down and nourish the plants nearby.

• 'Dig & Drop'

This is the easiest way to trench compost. Collect a large bowl of material eg. vegetable and fruit peelings. Simply take it into the garden, dig a 30cm (12”) deep hole wherever you can find a spot, put in the kitchen waste and cover it over. It's fast, easy and requires very little digging.

Sheet mulching

Sheet mulching is a relatively simple technique for creating gardens rich in organic matter or dealing with extremely weedy areas. The basic concept is to place layers of a variety of nitrogen and carbon rich materials on top of the soil, allowing them to break down naturally over time –in essence, composting right in the garden itself. Sheet mulching in various forms has been practiced for hundreds of years by small farmers worldwide and has been making a come-back in North America in recent years. Sheet mulching also goes by the names of sheet composting, lasagna gardening and permaculture gardening.

Why sheet-mulch?

Sheet mulching has several useful applications for the urban environment. It is a very effective way of transforming unwanted lawn space into growing areas for vegetables, perennials, shrubs and trees. It is also an effective way of dealing with very weedy areas, as the weeds themselves are decomposed in the process, adding their nutrients to the soil. Sheet mulching is a relatively inexpensive, quick and physically less demanding way of converting lawns or dealing with weeds as it does not require digging and turning of the soil. Sheet mulching is also an excellent way to make use of large amounts of organic waste material and has the benefits of other mulching techniques such as improving water retention in the soil and the prevention of soil compaction.

What materials can be used in a sheet mulch?

Just like in a compost pile, it is important to have a balance of nitrogenous (green) and carbon-rich (brown) materials. Suitable nitrogenous materials include: grass clippings, green prunings and other yard waste; manures; coffee grounds; alfalfa meal or pellets; kelp meal; blood and bone meal, etc. Suitable carbonaceous materials include: newspapers (but not coloured flyers); corrugated cardboard (with the tape removed); dried leaves; shredded woody materials such as raspberry canes, small branches, etc.; wood chips or bark (for the top layer only); weed free straws; etc. Some finished compost is also recommended to introduce composting bacteria, fungi and other organisms into the sheet mulch. 

How do you create a sheet mulch?

Follow these basic steps:

1. Prepare the area to be mulched. Begin by trampling or slashing any taller vegetation and leave it to lie on the ground. If the ground is heavily compacted, poke holes with a garden fork every 30cm (foot) or so to a depth of 15 - 30cm (6-12 inches). Soak the area well with a garden hose or sprinkler.

2. Add soil amendments (optional). If your soil requires amendments such as dolomite lime, rock phosphate, or other minerals, add them now.

3. A layer of nitrogenous material – Add grass clippings, manure, etc. to a depth of 3 cm (1 inch). Wet down with the hose.

4. Newspaper or cardboard – Provide a ¼ inch layer of newspaper and/or corrugated cardboard, overlapping sheets by a minimum of 6 inches. This layer ensures that the weeds or grasses will not grow through the mulch. If the area is very weedy, this layer can be increased to ½ inch in thickness. Wet down thoroughly with a garden hose.

5. A layer of nitrogenous material – allow another 1-inch layer of green materials, manure, etc. You have now “sandwiched” the carbon (newspapers) between two nitrogen layers, ensuring that your soil does not become depleted of nitrogen while breaking down the newspaper. Wet down with a garden hose.

6. Additional carbon materials – add a 1-3 inch layer of leaves, straw, finely shredded branches, etc. and wet down thoroughly once again.

7. Compost layer – A 1-3 inch layer of compost will ensure that you are introducing sufficient beneficial bacteria, fungi and other microbes into the sheet mulch. This layer also allows you to plant some plants into the sheet mulch without cutting through the newspaper layer. Wet down with a garden hose.

8. Soil layer (optional) – If you have it available, you can add a 1-3 inch layer of soil on top of the compost. If you chose to add this layer, be certain that the soil is relatively free of weed seeds. Moisten with a garden hose.

9. Finishing layer – For aesthetics, moisture retention and to reduce new weeds from germinating, add a 2” cover layer of wood chips, bark mulch, or another material. Compost can also be used as a finishing layer though it will be more prone to germinating new weed seeds. Leaves can be used as an effective top layer if they are in a protected area and will not be prone to blowing around.

How do you plant into a sheet mulch?

Plant trees and shrubs prior to sheet mulching and work the sheet mulch around them. Do not allow sheet mulch materials to come into direct contact with the trunk of trees or shrubs. Perennials and annuals can be planted into the compost and soil layer or pockets of soil can be added into the sheet mulch to accommodate them. Their roots will soon penetrate through the carbon layers. It is best to transplant seedlings rather than seeding directly into the mulch as seeds can get lost in the materials.

What happens in a sheet mulch as time goes by?

The introduction of all of this organic matter creates a feast for soil microbes and soil  animals. Earthworms and other critters soon begin to feed on the newspaper and other materials, fertilising and aerating your soil in the process. In no more than two years, the newspaper and cardboard will have disappeared and the weeds will have decomposed as well. Some people chose to continually add new layers to the sheet mulch over time, employing a “no till” method of gardening.

No-tillage methods do not disturb the soil as doing so can change the nature of the soil. A way to do this effortlessly is to cut broad beans and corn off at ground level and leave the roots in the ground. This can also be done with Amaranth. 

Happy gardening!