You may remember that my yard floods when in rains. The conventional solution is to treat the water like a problem, and drain it off the property as quickly as possible, usually to a storm drain. I however, wanted to keep it in my garden, allowing it to infiltrate into the soil to replenish the ground water supply. My initial solution was to grade the yard, directing the water into a swale, which would direct the water into a created lower elevation at the back of the yard, creating a vernal pond. This, obviously, has yet to happen. And El Nino, with its forecasted 3-months of solid rain, is coming.
Since last winter, I’ve spent some serious time thinking about my situation, and revisiting my resources on land-based water harvesting. Swales, the go-to solution for allowing water to infiltrate into your soil, are used on contours of sloping ground. My ground is not sloping. Its dead flat. We had it laser leveled, and had only a 1/4″ differentiation in certain areas. In addition, one of the first rules in using earth-works for water harvesting is you need soil that drains within 48-hours, such as mentioned in this great Sonoma County stormwater management resource document. We all know that’s not my yard! In addition, swales are usually used to slow water that is usually coming FROM somewhere, like a hillside or a pipe. My issues is my water source is the sky, and starts when it rains faster than the ground can absorb it. Instead of contemplating how to shape the earth to solve my flooding issues, I shifted to focus my thinking on my soil in general.
Now Entering Soil Science Lesson!
Soil is the thin outer layer of the earth’s crust, made up of weathered parent rock and minerals, living and non-living organisms, water and air. The amount and type of parent rock present determines the soil texture: sand, silt & clay, listed in decreasing order of size. Think of it as the ingredient section of a recipe. The ideal (and elusive perfect soil gardeners all dream about called loam) would have a combination of 40% sand, 40% silt, and 20% clay. From there, those soil ingredients adhere together to form larger particles. How those particles are arranged can affect things like nutrient availability and drainage. Sand particles, for example, are either rounded or angular, but they have lots of space between them for air and drainage. They could be compared to the balls in a ball play-pin, they move around each other freely, with gaps between each individual unit. Clay particles, however, are arranged in a way that could be compared to a stack of plates. They have the greatest surface area, but water is held very tightly and passes though very slowly. Which is why my half-acre of Adobe clay can’t absorb heavy rain!
So I started a new way of thinking: I needed to turn my soil into a giant sponge. In the ideal world, I would have thought of this from day one, and gradually worked my soil. But I didn’t, I thought of this about a month ago when I started El Nino Prep Mode. I needed a relatively easy, inexpensive (ideally, free), and fast way to increase water absorption throughout my yard.
My solution: spreading horse manure everywhere in the areas where the standing water is the worst. If you’ve ever had to muck out a stall in the rain, you know how heavy that crap can be, because it holds liquids. I connected with a horse stable nearby. They had a tractor and were happy to load our truck with as much of their manure as we wanted. From there, we squeezed the truck past the house to the back yard, and unloaded and spread the manure around to a layer of about 6″ thick. After several trips, we spread about 15 yards, covering most of the major flooding area. Its days like this that I really miss my dad’s dump truck.
From there, I threw out rye cover crop seed, and gently raked it in. This manure wasn’t composted, but horse manure doesn’t run as hot as other types of poo, so I felt it was unlikely to burn any seedlings. I’ve seen oat grass grow from manure piles, undigested in the poop and dropped feed, so I was pretty sure the rye would sprout despite not being planted in soil.
I chose rye because it germinates in less than 45 degrees, is cold hardy down to the 20s, and fast growing. I was planting these seeds late, the last week of November, and we had frost expected. I wasn’t concerned with nitrogen fixation, often the purpose of planting cover crop, but with improving drainage and loosening the clay soil. Rye has long roots, which will help break up the underlying adobe and help integrate the manure down into the clay. Rye can also deal with poor drainage, which is always critical in clay soil. When we cut it down in the spring, it will add significant organic matter, furthering the improvement of the soil.
The rye seeds sat for about a week, nothing happening. I was concerned they weren’t going to sprout, but once we got some rain, it started to pop right up. Now, its about 4″ tall. We’ve had about 4″ of rain to date from a handful of rainy days, which I think is more than half of what we got in totally last year, but I don’t have any standing water issues. I don’t think this quick fix has completely solved my problem, but I think its going to help!
In case you were wondering, why didn’t I just add sand to my soil to increase drainage? It seems like common sense- water does drain very quickly in sand. But sand and clay make cement, so it would actually make things worse. If I wanted to add sand, I would need to have mixed in equal amounts of organic material: difficult (and expensive) to do by hand.
Next up, on El Nino Preparedness: digging ditches to drain the downspouts!