Yeah, I should be working on my thesis right now and instead I was reading a garden blog and procrastinating. I prefer to think of it as "cogitating." Anyway, this brief note got me a bit riled up. The gist of it is that since 40% of carbon emissions come from tilled soil, home gardeners should not till. And possibly mulch will hold carbon in.
There are a couple of problems with that thesis that seem fairly obvious to me. First of all, that 40% of carbon emissions is not coming from home gardeners. It's coming from large-scale agriculture. Whether I till my garden or not is a miniscule amount compared to the massive problems of large-scale agriculture. Second, mulch itself emits carbon, as do all decomposing organics, and its production causes carbon emission.
So the entire thesis misunderstands how carbon emissions happen. But behind it is a belief that tilling is bad (and I generally agree there, except in cases where you are tilling organic material into infertile soil for crops, which is why most people till their gardens) and mulch is good.
Mulch, alas, is not the wonder-drug of gardens. For one thing, it keeps the upper layer of soil moist, and the upper layer of the soil is not where the roots should be -- the lower layers of soil don't dry out as fast as people think they do unless a plant uses up the water there, and in that case mulch is not going to help you. Mulch attracts pests, or worse it carries pests from wherever it came from. It absorbs moisture that could go into the root zone and then allows it to evaporate, wasting water. It's doesn't even really stop weeds, especially our pernicious Bermuda grass. And most of all, it is generally in the process of decomposing, which uses resources your plants might want.
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