Have you tried solarization? Till up your soil,water it,and cover it
with clear plastic. Keep it covered for a couple of months and let the
sun "do the dirty work"! I have to admit that I had my doubts when I
first read about it, but it really works! Acouple of bonuses; it also
seems to kill some pests and pathogens too.
We divided our garden plot into 3 sections and include solarization
into our rotation. I also plan ahead when adding a new flowerbed and
solarize the summer before planting.
I have also read that you can leave the plastc on until spring and
plant without tilling.I tried to do that this summer with a particulaly
weedy plot,but unfortunatly,I ran across a salesman who sold me plastic
without UV protection and our brutal summer here ate it alive. After
only 2 months,it started to disintigrate and I spent 2 hours picking up
all the schnibbles of plastic!
Make sure you get UV protected plastic!