Creating topsoil

[Mtsoxfan]

I've been making topsoil for years, mostly grass clippings and shredded leaves, and tilling 3x a year. If it's too moist, I would mix in sandy soil. Always worked great.
Fast forward to new home. Neighbor has horses, and has an area where he has dumped manure. At least 6 years old. Mix of manure, long grasses, some sand. I have been mixing in culvert cleanings, mostly sand. Looks like good soil. Will use for topsoil for a lawn I want around patio.
My pile is about 8 foot tall, 16 foot diameter. It is now covered with dark tarp and in sun 8ish hours a day.
My question is this, how long would you estimate it to take before any "seeds" that are in it are sterilized, so I will have "clean" soil?

 

[JJT]

Sounds like you have a good handle on this project.

For a lawn, don't agonize over the weed seeds. You're going to keep it mowed and most of the seeds in horse manure will be of the grass variety.

 

[Ken45101]

I think JJT is right, keeping the area mowed will kill off most of the undesired seeds that germinate. It's as different story than using the composted manure in a garden.

Ken

 

[big bubba]

actually you're creating compost, not topsoil. turn & water occasionally. for the pile to completely process the organic matter, you'll probably have to add nitrogen of some sort, commercial fertilizer is convenient. maybe monitor the heat. (the several yr old manure probably is insufficient nitrogen). this is an aerobic process so not sure covering pile will do the compost any favors.

agree with above posters, the weed seed may not be a big deal. (you can always test samples for germination) completely composting the pile imho is more important. so water, nitrogen, & aeration would be the key points. the temp range for a properly composting pile is generally between 90-140 F. when it no longer heats, it's ready, prob in several months. good luck with your project

 

[Mtsoxfan]

thanks all...

 

[amhicks21]

Just wanted to toss my 2 cents in since Ive been making quite a bit of topsoil over the last few years. From what I can tell, the decay process of the yard waste also rots any seeds in the soil quite quickly so by the time grass clippings and leaves have deteriorated, so have any seeds. I have about a 60 yard pile screened from 2 year old lawn and landscape waste that hasn't sprouted a single weed yet despite the back having been screened almost a month ago.