Question
I am building a new lawn in Grants Pass, Oregon. Climate zone 7. My soil is primarily red clay with granite underneath. I have access to a commercially produced compost made of wood products mulched and mixed with some kind of fertilizers/ decomposers. I also have access to horse/ cow manure. Someone has already purchased Canadian Green grass for me. At present the ground is uneven, on a downhill angle, compact and practically devoid of life ;) My tentative plan was to rotatil the clay, even out the surface, bring compost in and lay an even layer, then bring in horse manure and mix it with the compost. Following this resurface the new topsoil and seed the grass. I am not sure whether it would be better to mix the compost with the clay or avoid the clay altogether and just grow the seed in my new topsoil. I am open to any advise. How deep should the new soil be? Can I mix it with the clay? Is horse/ cow manure any good for grass? I do have some weeds that I considered using Roundup on but I was told that nothing may live in the area for a couple of years if I did so. How should I get rid of the existing weeds? How long do I need for the grass to establish itself before fall? How much seed do I need to plant and how do I measure that amount when planting? You name it I could use advice about it.

Thanks,

JIm

Answer
Clay soil is just fine, and you will get a very good result if you mix in organic material, such as manure or compost into the soil.

If you can, roto till the soil to a dept of 8-10" (or whatever the machine does) and spread cow, horse manure and compost. Then till these into the soil, too.

If the cow and horse manure has not aged (e.g. it is fresh) then it should be composted first. Fresh manure can do a trick on new lawns. You can also apply and roto till the manure into the soil this late fall but then postpone seeding until next spring. Fall is preferred time to sow seeds, but it is more important that the materials you mix in have time to age (do not try to sow seeds with fresh manure).

Your description of the "compost" makes me think that it is not "compost" yet. The wood products tend to tie up nutrients (nitrogen) in the soil and this is probably why it is mixed with fertilizer to begin with. This "fresh compost" has not been allowed to age properly, and it may 1-3 years to do so properly. If the wood was fresh when ground (such as chips made from trees cut down) then I don't recommend using it for 1-3 years. Then this is really not compost .. yet. Compost is carbonrich materials which are mixed with nitrogenous materials and allowed to age. Unless you know that the compost has aged properly, then you could get problems until the aging is complete. You can put the "compost" (wood/fertilizer mix) in a large pile and allow it to age for a couple of years and then use it. It is excellent as compost, but it is just not compost yet.


I suppose you could mix 50% wooden "compost" with the manure (50%) and then leave this mix in piles for the rest of the summer. Turn a couple of times after the piles heat up. Once it no longer heats up, it should be safe to roto till into the soil for the winter. Then reseed next spring.
The piles should be minium 3 x 3 foot x 3 foot (1 cubic yard). you can use chicken wire in rings to hold it together or you can make 4 high x 4 foot wide windrow's as long as you need. Remember to turn after they cool down. (Compost 101 lesson complete).

If you now that the compost/manure has indeed aged properly (or been hot composted already) then it is safe to roto till into the soil and to see immediately.

You can roto till into the soil and allow a few weeks to settle. Then rake smooth. Apply grass seeds in september and keep seedbed consistently damp until new grass germinates (if seeds are allowed to dry out after planting, they die. Water several times per day or cover with straw.. not hay which contain own seeds ..). Once new grass sprout, you can gradually change from frequent and shallow applications to watering infrequently and deeply (such as once per week for 1 hour). Start to mow as soon as new grass is 2.5-3.5" tall.

Round-up is a good way to kill weeds. Round-up is taken up through the leaves and will prevent the plants from eating and they die. Once the product is dry, it is not going to interfer with your lawn. It does not reside in the soil and it does not translocate. Once dry (a few hours) you can till the soil and plant seeds. I like to wait a few days until the weeds die to see if I missed anything, though. You do not have to worry about Round-Up, but be careful when spraying: do not spray on windy days and do not spray flowers, shrubs, etc.

Use about 8-10 lbs of grass seeds for new lawns per 1000 sq feet. You can find out how many sq feet your lawn is by multiplying the length x width of each seperate area and then adding these together. Say you have an L-shaped lawn consisting of one area 100 x 50 and another area 50 x 200. Your lawn would then be (50 x 100 =) 5,000 + (50 x 200 =) 10,000 = 15,000 sq feet. You would then need 120-150 lbs of grass seeds (8-10 lbs per 1000 sq feet). Put seeds in a fertilizer drop spreader (which is a plastic bucket on wheels with a cable release). The drop spreader can be purchased at home improvement stores and it costs very little (drop spreader preferred over rotary spreader for seeds, and is cheaper, too). Run over the lawn in various directions pushing the spreader like lawn mower. Make sure the opening is at the maximum (largest) setting to make sure that the seeds are evenly spread. You can also spread by hand, but make sure coverage is even/complete.

For best result, ensure good soil/seed contact by using back of rake to stamp the seeds into the soil, or by walking on the seeds. You can also cover with straw.

Remember to water.

A lawn established in fall will do well because it can go through another active growing season (spring) before a taxing summer. Summer is actually worse than winter for grass. Therefore, planting seeds in late summer/early fall just as the daytime highs go down (early september) the soil temperatures will be warmer than air temperatures and that will result in fast germination (sprouting) as long as you keep the seed bed well watered. The grass then have ideal conditions during sept/oct to grow and settle in before winter.

Fertilize your lawn at time of seeding, and repeat again in late fall (late November). Then fertilize again in late spring. Do not fertilize too early in spring or during hot summer months. September, november and May are good times in zone7.


Good luck