Poor Crops, What can I do to impove ??

How much sunlight does the plot get?  This can be a big factor for a lot of crops.

Soil - how quickly does it dry out?  Some of my potato and garlic yields this year was well down because it got hot and dry and I underestimated water needs at a time they needed it to bulk up.  The Leylandi hedge could be taking a lot more moisture out of the ground than you realise.  Why not try trench composting for the runner/french beans (basically dig a trench about now and throughout winter add kitchen waste such as tea bags, fruit & veg peelings except potato etc, then in late winter/early spring cover the trench with soil and leave it until you are ready to sow/plant beans in late spring)  Beans can be thirsty plants and the compost will help to retain moisture during the hot weather.  When watering during hot weather, give the ground a thorough drenching (push your finger into the soil to see just how far the water has gone - even when the bed looks saturated and puddled after watering, if it has got too dry you'll be surprised to find that you'll need a lot more water than you realised)  Onions need water to bulk up and if I remember, it was hot and dry in July when they needed it the most.

Soil nutrients - maybe you need to add more than manure.  High nitrogen levels can give leafy growth at the expense of root or fruit crops so maybe you need to boost potassium and phosphorous levels, and then there are micro nutrients such as magnesium, manganese, calcium, iron etc needed for plant health.  You say you feed once a week - with what?  Different fertilisers have subtle variations in nutrients for different purposes (high nitrogen for leafy growth, high potash for fruit and flowers)  Maybe rake in some general purpose fertiliser into the soil a couple of weeks before sowing/planting - look for a brand that contains the micro nutrients in case something is lacking.  With regards to manure - the nutrients are not instantly released into the soil but needs to break down over time, so it might explain why some things did better this year than last year.

Soil pH - that Leylandi is troubling me and makes me wonder if it could be affecting the plot.  Soil pH affects the uptake of nutrients.  If the soil is too acidic, then some crops like brassicas and beans don't do so well.  Maybe you need to add some lime to lower the pH (you can put a handful into the planting holes of brassicas)  Don't forget to heel in brassicas as they like firm soil round their roots.

Weather - is actually the biggest factor of all    Last year was very wet so going back to the other points, rain could have leached out nutrients, not enough sun, affect soil pH and some crops did well, others not.  This year a very late cold spring (so the ground is cold and everything is slow to take off) quickly followed by hot dry weather (some things don't like hot weather, others do well) and plants react differently so it is difficult to compare one year's crop with the next - I think you'll find everyone will tell you that a particular crop did better or worse than expected and every year it is different.  I also found the temperatures see-sawed a bit this year - a hot spell, followed by a cold snap ... some plants might have got checked.

Numbers and spacing - if you planted too close, then they could be struggling for light, water and nutrients.  Likewise, keeping weeds under control is important for the same reason (onions in particular can get stunted if crowded)  Numbers - if you don't grow that many, then harvests might look dismal.  And then there are expectations - try not to compare your harvest with supermarket produce which is graded.  Also, genetic variation is a factor too - I can grow a row of say carrots, and some are humongous, some are tidgy all in the same row with the same growing conditions but overall the harvest would be fine.  If there were only a few, the harvest might look pathetic if you understand what I mean.

Crops - some do better than others in any given plot.  When I had 2 plots, they seem to be good for different crops.  Caulis are supposedly not a beginners crop so take heart if they didn't do well.  Leeks - they might fatten up a bit yet, or you might need to look at a different variety?  Did you dib a hole and pop them in, or were they just planted with the stems above ground?

Sorry it is a long post but there could have been any number of reasons why things have not done well.  Look on it as a learning experience rather than a failure and don't give up yet!

 

Hiya
Many thanks for the help so far & to pick up on a couple of points BabbyAnn brought up.
1/ During the summer months the plot is in full sun (if it's out) from about 10am till 6pm.
2/ The soil is very heavy with clay.
3/ Before planting we always dig in a good deal of Growmore about a week or so before & as I mentioned in my lengthy question water as & when required & use a tomato feed about once a week.
4/ The leeks, we have tried growing in the plot from seed, that didn't work at all & we have bought plants & dibbed them in but as I said they don't fatten up, this year they are about 3/4" thick at best & last year they were still like a pencil in Feb' so we gave up on them.
What we can't understand is why do the runner beans & rhubarb do so well & everything else we try is so disappointing.
Keith/Sharon 

The roots extend out to the middle path of my garden, ruining the lawn in that area and that's about 9ft.
So plants may need more watering than you think.

How and when did you sow your leeks, and then finally plant the shop bought ones? Leeks are often started off in pots or trays early in the year and transplanted out when big enough. They do need a long growing period to make large leeks, though. This may help.........
http://chat.allotment-garden.org/index.php?topic=26363.0

The only other thing I am wondering is whether you have carefully read up about growing each particular veg. A number of the things you have grown need special care to grow well. A lot of people struggle with cauliflowers for instance.
As Mos says, leeks need a long growing season and take forever to get to planting out size.
Your onion sets may have been planted too deep, it surprises most of us when we realise, for the first time, that they shouldn't be completely covered by soil.
Things like peas and broad beans if sown direct, may be eaten by mice or rot before even germinating. You also need loads and loads of pea plants sown in succession to get a good crop. If you were expecting a few meals off a dozen plants, it doesn't happen. Some varieties produce just a few pods per plant. So it could be that you simply didn't plant enough.
Not all plants need super rich conditions either, plants need to be a bit stressed to fruit. Beautiful looking tomato plants for example, probably won't produce as much fruit as some that look a little more unloved.
The thing is, as Babbyann writes so comprehensively, there are many, many things that could be the problem. But that is also part of the fun and the challenge and why it is so satisfying when we get some successes!
The folks on here have really helped me as a novice gardener with all their advice, and I know I wouldn't have done nearly so well without that wealth of experience to draw on. So, hopefully you will have a much better year next year.