QuestionI live in British Columbia, with zone 5b climate conditions. My lawn is south facing with very little tree shade. The soil drainage is quite good, consisting mostly of sandy glacial deposits and small boulders (dangerous to rotatill) and has a drainage rate of about 5 minutes per inch. It bakes over the summer months with very little rainfall between June and August. The area I would like to prep is quack grass now and has a septic field beneath, so there is grass growing well over the lines but nowhere else. Ideally I would like to install underground sprinklers but I have to take the septic field into consideration. I can install a check valve to prevent backflow but overwatering a septic field can decrease the field life. So I want to keep it to a minimum. Also we have water restrictions in summer.
My plan is to bring in a bobcat to level the area better first. I have about 6 inches of soil cover over my first septic line and 32 inches over the last one. It was made this way to compensate for the property slope but they overdid it. I'd like to have 6 to 10 inches of soil cover over these lines. This would create a slight drainage grade in the correct direction but would still be reasonably level.
What would you recommend for soil mixture preparation with the drought conditions in mind? Clay mix/topsoil/peat? The area is about 60ft by 90 feet. I'd rather not spend a fortune. Topsoil can be hard to find around here. How many inches of improved soil should I add to keep watering down to a minimum? I'll be planting a drought hearty grass mix and will have to look at some samples to find something attractive but practical.
Thank you for your time. Paul
AnswerIMHO, the old fashioned Cover Crop solution is the perfect answer to your problem, Paul. Rather than ship in truckloads of "Topsoil" (which will be expensive given that you point out it is scarce in your zipcode), or anything else for that matter, why not to improve soil fertility and quality instead? It's low cost and the most effective thing you can do to correct your soil.
In agriculture, Legumes - Green Manures - inject incredible amounts of Nitrogen into weak soil. They are usually tilled in before they reach maturity, improving soil fertility. But it's the special bacteria in their roots that makes them such great Nitrogen generators. And if there's anything you need to grow healthy grass, it's Nitrogen. Sure, you can apply Nitrogen fertilizer to your sandy soil 'til the cows come home. But if you are going to provide a steady, even Nitrogen dose, along with the 15 other minerals turfgrasses need to make a gorgeous lawn, you should fix the soil it's growing in. And the best thing about that is that it's cheaper and definitely better than anything you can dump over it.
Even if you are reluctant to 'til because of the possibility of hidden boulders lurking underground, you will still obtain fine results with Green Manures. Their roots are where all the action is. Rototilling does have its downside - the biggest in my book is that Earthworms head for the hills when you Rototill, and you want Earthworms to move IN and stay.
As an added bonus, the roots of some Green Manures draw nutrients upwards to the surface and make them available for your shallow-rooted lawngrass.
Still, it would be ideal if you were able to incorporate a cover crop into your sand at season's end - given that the Earthworm population is probably next to nothing anyway, and the sandy soil is almost sterile. A boost of organic matter is just what the doctor ordered for building up the soil structure. A Teaspoon of rich soil holds anywhere from 100 million to 1 billion bacteria. Improving soil porosity is the best way to encourage massive numbers of bacteria in your sandy soil. You want to encourage growth of soil microbes down there; you need those Nitrifying Bacteria in your neutral, nontoxic soil to break down the decomposing stems and roots, converting Organic Nitrogen into Nitrate, at a rate that changes with the temperature and natural pH, like natural clockwork. You cannot accomplish any of this with a mere truck or "topsoil" layer.
Your sandy soil will also benefit from improved moisture capacity. The Green Manure, or any cover crop, holds a surprisingly large amount of H2O. Whether you mow it down or till it in, you will increase moisture levels in the soil. The Earthworms will go forth and multiply. All of which is a very good thing, my Canadian friend.
Besides, all those trucks will compact the soil even more. There goes the Oxygen level underground; there goes your good Nitrifying Bacteria.
My vote is to keep the trucks off the future lawn and plan to sow your first Cover Crop. What do you think, sir?
