Subtitle1: My physical fitness program

Subtitle2: How to continue to improve your soil during a drought

Hello everyone. I thought I would post some photos of my trench composting project. I've been working on this for several years in different parts of my garden, trying to improve the texture of my clay soil, especially in the zone from about 8" to 24" since I eventually want to plant fruit trees and grape vines.

I live in N. Calif, an area with hot summers that normally gets less than 16" of rain/year (almost all of it from Nov-April), and I have a clay loam soil with a very dense clay zone from at least 12" to 36". An initial soil test showed pH = 7.8; 4.5 % SOM; low N, P, K; high Ca, Mg, Zn.

I've been digging and tilling my soil deeply and adding large amounts of organic matter, however, I find that with little rainfall and hot summers, the window for really productive biological activity in the topsoil is relatively short (unless I irrigate, which has been impossible with recent droughts and water use restrictions). I suspect almost all beneficial activity by soil organisms in the topsoil occurs in 8-12 weeks between March and May. This is not a region where the soil is moist and warm for 6 or more months of the year.

I noticed that by digging in areas where I've buried large amounts of organic material in a trench, after a year or two, the soil profile shows a zone of dark, friable soil, indicating that decomposition proceeds unabated in the relatively moist and stable environment 1-2 feet underground. So I've taken this to the extreme and my current procedure is to dig a 12-24" deep trench and then fill it completely with organic material. Then I dig a new trench parallel to the first one and throw the soil on top of the first trench, stopping occasionally to throw more organic material on this excavated soil and a thicker layer over the top. This is sort of a variation of the double-digging or deep-bed method. For organic material, I've used waste produce from grocery stores, wood chips, my compost heap, etc., but the primary material now is horse stall waste (75% sawdust, 25% urine + manure?) because it's abundant and free in my area.

The first two photos show trenches being dug and the last two photos show filled trenches, in one case with the contents of my compost heap and in the other with a mixture of sods and horse stall waste.

I highly recommend this for anyone who feels like they aren't getting quite enough exercise.