Permaculture soil survey

As part of our attempts to properly design our gardens and land we decided to conduct a thorough soil survey, to determine what kind of soil we have, and what potential problems we might have with the soil.

Methods

Three test sites were chosen, to reflect the range of soil types in the garden. Test site 1 was near the open barn, on land that has been cultivated in previous years, but near the edge of that land. Test site two was in the middle of the site, on land that has been intensively cultivated in previous years. Test site three was in the ‘orchard’, where the land has been less intesively farmed.

The Tests

Drainage Tests

Drainage
Drainage

This test shows how long water will take to drain away from the lower levels, underneath the topsoil. It will indicate any potential problems with long-term water drainage.

Method – Dug a hole, 15cmx15cmx30cm deep, filled it with water and allowed to drain. Re-filled with water and measured the time taken to fully empty of water.

Results – Test site 1: 92minutes, test site 2: 195 minutes, test site 3: 68 minutes

Infiltration tests

Infiltration test
Infiltration test

This test indicates any problems with immediate water drainage from the topsoil. This will mostly relate to sudden downpours of rain, and how long this may take to clear.

Method – Stuck a clear plastic pipe 4cm into the ground. Filled the pipe to 20cm, then measured how much had draied out after 10 minutes

Results – Test site 1: 5mm, test site 2: 0mm, test site 3: 4mm

Worm activity

Worm activity
Worm activity

This test indicates the level of worm activity in the soil, and is a useful indicator of general soil health – the more worms, the healthier the soil.

Method – Dug a hole 30cmx30cmx30cm, counted the number of worms in each sample. Baby worms were ignored, and I dug up a recently hatched batch in test site 2.

Results – Test site 1: 10, test site 2: 1, test site 3: 10.

Bacterial activity

Bacterial activity
Bacterial activity

This test indicates the level of bacterial activity in the soil. Bacteria are crucial to the process of decomposing organic matter into loam, and making minerals and nutrients available for plants.

Method – Cut strips of unbleached cotton cloth. Made a slit in the soil with a spade, then inserted the cloth into the slit using the spade. Six samoples were made at each test locatoin, samples removed at four-day intervals and examined for decomposition.

Results – test not yet completed

Surface decomposition

This test shows how rapidly surface organic matter is being processed into the soil – the more mixed the matter is, the better. A high degree of separation indicates that organic matter is not being processed rapidly.

Method – Top layer of mulch was scraped off underneath a tree. The boundary between soil and mulch was examined, and an assement made of the distincness of the layer.

Results – distinct boundary between soil and mulch, indicating not much migration of material between the two layers.

Conclusions

We have a very heavy clay soil. Drainage is poor, both in topsoil and lower layers.

Test site three, which has been less intensively farmed than other areas of the garden, seems to have significantly more worm activity and better drainage.

We are not going to be able to significantly change the soil type – it’s clay. We will therefore need to look at the types of plant we grow, espcially permanent plants like trees, and choose varieties that will do well on clay soil types.

We will look at growing crops more on top of the soil, in a mulch of composts, rather than in the soil, if they will not tolerate this soil type.

We will step up our compost production. We are especially short of green leafy material, and will probably grow some green manure crops at our other site to improve the compost mix so we can compost faster.

We must not let our soil become uncovered – this leads to a significant drying and hardening of the soil surface, which is not conducive to increasing worm activity. Instead we will cover exposed earth with a thick mulch of straw or other material, or, if being left uncovered for a significant period, plant a cover crop of green manure, which can be later worked into the soil.

  3 comments for “Permaculture soil survey

  1. Robyn Richardson
    April 18, 2015 at 5:46 pm

    The work you two do is incredible! I’m impressed.

  2. April 18, 2015 at 10:52 pm

    As with Robyn, I’m SERIOUSLY impressed with the thoroughness of your tests, but if you are reliant on the food you grow, it’s a worthy effort and time we’ll spent.
    I had similar soil in Wales. You have to keep digging in barrow loads of manure from friendly farmers and it does eventually start to break the clay down. Best to dig in and leave a while if you can afford the time to? If not, raise your beds!
    In awe, as ever!

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