Irrigation & Soil Conditions

I have a question about watering & soil conditions that I hope you all can help with. I hope that I can explain myself properly and it doesn't come out garbled.

I live in the San Francisco Bay Area where we have a wet season and a dry season. No rain from May to November. I have sandy/clay soil. I have an automatic irrigation system with spray heads attached, that waters the grass and all the garden beds. One of the gardens is in baking sun all day and I had roses, canna's and elephant ears growing in it. All heavy water users. I had heavily amended the soil with compost prior to planting and mulched with at least 3 inches of bark. I irrigated once a week for around 15 minutes and then occasionally let the hose run while I was weeding etc. The elephant ears - the most delicate plant of the lot and more suited to warm shade - stood up to the heat and the sun and the other plants thrived. The soil under the bark was damp and loaded with worms and starting to get into great condition - all nice and soft and dark and crumbly.

The spray irrigation works great on the grass areas and is good for washing the dust off the plants in the gardens, but I hate over-spray and water wastage. Trying to avoid both of those is quite difficult so at the beginning of this year I had my DH replace the spray heads in the garden beds with drip irrigation and I relocated the canna's & EE's. This weekend I was adding other plants to this particular bed and found that the soil is dry, full of clods, & has hardly any worms & loads of ants. It was very difficult to work with.

So my question/concern is that drip irrigation is not the best choice for soil health. Does the soil need more water than it is getting to maintain it's condition and all the organisms that live in it? Should I be (yikes) replacing the drip back to spray irrigation? Is drip a better choice for say, vege gardens but not perennial or shrub gardens?

I would welcome any and all comments. TIA.

Hi wgnkiwi,

As an ex-Redwood City gardener, transplanted to West Texas, I have learned that drip irrigation is not the best method in all cases. I have 2 food gardens, both with sandy loam soil (or maybe loamy sand). One has beds enclosed by 2/8's in which I grow veggies and herbs; it has been going for 3-4 years, so the soil is getting pretty good. After many applications of compost it has that chocolate cake texture and holds water fairly well. Drip works fine here, with the lines 10" apart, emitters every foot. I found that having the lines 13 or so inches apart (3 to a 40" wide bed) was leaving dry areas.

In the "orchard" garden I used to have a circle of drip line around the small trees, and for at least 2 years, I realized later, the poor trees were starving for water. They did not look great and were being attacked excessively by insects. The soil in this garden, a much larger area, still does not have sufficient humus and drains very fast. This year I dug out deeper, wider basins around the trees and after adding compost, I mulched with a thicker layer of alfalfa hay and pulled weeds. I removed the drip lines and just water the basins well by the hose every so often. Result: the trees are lush and thriving - what a difference!

hey kabocha, Redwood City huh? Im always surprised by how much warmer it is down there when the distance between Burlingame and RC is only a few miles. My DH and I tried to buy a lovely house there but got shut out in a bidding war. Crazy!

My vege garden has lovely texture after only two years of amending, although I started it by double digging everything. This last winter I covered the whole thing with clear plastic in a bid to stop the rain from washing it all away. It worked pretty well.

What has surprised me is it looks like compost has never been added to the other gardens. Where did it go? At this point I'm thinking of removing all of the bark mulch and mulching with compost & lawn clippings which is how I used to garden.