Chop and Drop: Leaving Plant Residues in the Garden

Image from California Agriculture

Since 2004, University of California scientists have been studying “conservation tillage,” a suite of techniques that includes practices such as reducing tillage and leaving crop residues in the field after harvest. Leaving crop residues, in permacultural lingo, “chop and drop,” it turns out has a number of important benefits.

According to a research paper in the April-June 2012 issue of California Agriculture,

In two field studies comparing no-tillage with standard tillage operations (following wheat silage harvest and before corn seeding), we estimated that 0.89 and 0.97 inches more water was retained in the no-tillage soil than in the tilled soil. In three field studies on residue coverage, we recorded that about 0.56, 0.58 and 0.42 inches more water was retained in residue-covered soil than in bare soil following 6 to 7 days of overhead sprinkler irrigation. Assuming a seasonal crop evapotranspiration demand of 30 inches, coupling no-tillage with practices preserving high residues could reduce summer soil evaporative losses by about 4 inches (13%).

While this study is about commercial agriculture, much of its findings apply to home gardens as well, in my opinion. Leaving residues from the previous crop as a mulch layer saves water and builds soil. It does, of course, make it harder to direct sow seeds, but this is one of the reasons I like to work with transplants.

So don’t keep that vegetable garden too neat!

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  1. I thought that leaving behind the previous crop could spread diseases? Is that not the case?

  2. Diseases are one drawback of this practice and this factor is listed in one of the charts in the paper. My guess, especially in California’s warm Mediterranean climate, is that residues have more advantages than disadvantages especially when it comes to retaining soil moisture.

  3. After reading a book last month specific to Western Wasington, I would agree with the author on not using a fluffy mulch from plants and straw. I would add a layer of finished compost around the plants. If the bed was lying fallow I wuld put down a layer of leaves because worm activity increases during the rest period. We are so wet here and run rampant with slugs and bugs that munch. Chickens can help but are too aggressive during growing seaons and I don’t believe in pestacides although my husband is a great slug hunter with a flashlight after dark.

  4. It’s all about organic matter and soil biology. How many of our ag issues stem from using Ginormous Machines to replace people?

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