Question
I just bought a 1 acre ranch home. I have a big lawn area in the back yard that is uneven ground and more weeds than grass. I have alot of trees with exposed roots showing back their to.I would like to level the area and start growing new grass.I would like to bring in fill dirt, level the area off over the tree roots. And than start growing new grass.Should I kill the grass with roundup first than bring in the fill dirt.  

Answer
Hi Brad Kirby,

>>"...Should I kill the grass...?"

If you plan to seed the areas with a certified named cultivar of grass seed such as 'U3 Bermuda' or 'Plantation Tall Fescue',...then YES I do recommend that ALL vegetation be spray-killed before seeding.

This way, your new lawn will be a pure stand of a grass type, and this should look better than any sort of resulting mix. ROUND-UP should do a good job of killing all non-woody herbaceous weedy plants.  It will have no effect on woody plants and vines like saplings and poison-ivy. Round-up will also not affect plants that are now winter dormant (including weedy Bermuda grass) or plants with tubers/rhizomes under-ground.  The existing top-soil also probably has zillions of wild weed seeds in it.  Round-Up will not kill these seeds or anything without an exposed green-leaf.  Many of these dormant weed-seeds in the top-soil may sprout in the weeks ahead.

If possible, you can prevent some of these persistent weedy problems by under-tilling/roto-tilling the top-soil while adding any soil amendments or new top-soil.

You will probably also have to use some of the other weed-fighting chemicals for these persistent weeds.  If your lot is near any wild areas, there will be continuous weed-seeds blown in to sprout on your new lot and lawn.  Getting to the point where you can use a POST-EMERGENT HERBICIDE will make your lawn eventually weed-free.  Note that you cannot use this type of chemical until all the turf-grass seed is up and going.  

Incidentally,...
Depending upon the type of tree,...exposed  tree-roots can be a problem for mowers;... and covering some of these with top-soil will not stop them from popping up again. Such trees as Asp, Sugar-Gum, Maple, Mimosa are particularly bad about this.  You may want to have some of these types of trees removed or replaced with other species before they become a continual problem due to exposed roots.

A top-soil can ALWAYS be improved.
While you work to become weed-free in the areas to be made into lawn, you might also consider working to improve the top-soil by adding better soil.  Most top-soil suppliers will sell something called  a 'Rich-Mix' blend, and this will be the best soil to add to your lot.  This can do much to make greens-keeping a much easier task in the future.

If your existing top-soil is particularly of good tilth and fertility and has good drainage, you do not need to add anything to it.  But most new lots can benefit from adding amendments.  Usually, you can decide about this by just taking a shovel to a few areas and examining the soil, or you could have the soil lab-tested.  If wild grasses and weeds are growing OK, the soil is probably good enough for most hybrid turf grasses. It can always be improved over the years by top-dressing the weak areas.

You may also want to consider installing a sprinkler-irrigation system at this time.
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