Hi there guys, I managed to get half an allotment off my local council which measures 12 meters by about 6 meters workable area.
unfortunately the heavy clay soil is holding on to the water and it looks like the Somme at the moment. I've put up a 12 meter long by 3 meter wide poly tunnel to help keep the rain, slugs, cats and birds off next years crops.
I researched how to improve clay soil on the internet and it suggested adding sawdust and horse manure in large quantities to improve the soil and help drainage possibly sand as well.
As well as that I was looking at getting a manual corkscrew post hole drill to drill many 3 foot deep holes all over the place to drain the water.
Does that sound like it'd work? it does to me but I'm a complete newbie in the art of drainage and soil improvement so any advice would be greatfully received.
First get loads of horse muck, and sharp sand not smooth building sand, sawdust is OK so long as in general its from hardwood cuttings not softwood or pine. Now either hire a rotivator and dig it all in, or go the alternative route of building raised beds.
if you go raised beds you dont have a frainage problemn if you choose to work the lkand find the lowest spot on the plot and dog a decent hole at least 4 ft deep 18 inches wide and fill it with pebbles, rubble, gravel etc to act as a soak away.
It has been a bad year for rain and on any worked ground I look at as soon as it rains now it looks bad. With your new ground, I would dig a hole probably 4ft deep and see what you have - depth of top soil, clay, sub soil so you have an idea of what you have to work with.
If I had thin top soil on top of clay (as I have had with every garden I have worked) I would properly double dig it but you have to do it before mid winter as you need the frosts, as many as you can get. Dig out to a spades depth and store. Dig out the sub soil and clay and store to another spades depth, break up the bottom of the trench with a fork. Add manure or compost if you have some to spare. Dont matter if it is well rotted or not, add it.
Dig the next trench and put the top soil layer on the bottom of the first, the clay you are digging out next goes on top. This goes against common wisdom of not inverting the soil, but the frosts will help to break the clay. All the better if you can mix in manure or compost with this layer too. You can add old plasterboard to clay, the gypsum helps the clay to break apart, what is called floctuation.
If you can get slag from a steel works in your area cheap or free then this is good to add too.
In reality, you need to do several things:
1. Break up the layers underground that are stopping the movement of air, water and restricting roots
2. Break up the clay to help with the above
3. Add organic matter to act as a sponge for water, soaking the excess up and storing it along with promoting soil life and acting as a nutrient store.
Do a bit at a time.
If you can get your hands on the manure but do not have the time to dig, spread the manure on the ground evenly, will protect the soil over winter and make it very easy to dig come spring. This way you are getting the worms to do the digging for you, you can keep doing this. Will take longer to achieve your results but they will come in time anyway.
What ever you do, loads of manure each year, you cannot get enough.
We had same issue as a kid in our garden. My dad had us dig trenches throughout the area which were filled with pebbles etc making kind if pebble drainage. He then put a shit load of top soil in ( easy to do as we lived on a building site and he had 2 young sons to bring him as many barrow loads as he needed). It was a lot of work but it certainly made a huge difference to the drainage. Good luck!
I have heavy clay on my property and IMO the best way to grow crops on this type of land is to use raised beds. Put as much compost etc as you can get onto the beds, continue adding compost at every opportunity and in a few years you will have great soil. Clay is actually one of the richest types of soil as it is full of minerals, but they are locked up, once you start to break clay down you can grow anything on it.