Evaluating mulches

I’ve now used three different mulches/soil conditioners in the vegetable garden and so you may be interested in some comparative comments. They are mulched bracken, sugar cane and pea straw. I usually put a generous layer on top of the soil as mulch and when the particular crop is finished it gets lightly forked into the top few centimetres before the next crop is planted.

1. Mulched bracken

This grows on our bush property and so there’s any amount always available. Put through a small chipper, it makes a coarse mulch.

2. Sugar cane

I buy this at Bunnings for about $17 per compressed bale. It’s claimed to be organic and the packaging says it will cover 8 square metres at 5 cm depth.

3. Pea straw

I buy this from a local feed supply store for about $13 per bale. No idea on coverage, but I think it would be at least as good as the sugar cane.

OK…..comparisons.

Price: Bracken wins out here. It’s free.

Obtaining it: Bracken wins out again. It’s growing all around me. The only drawback is, I have to cut it and mulch it. Time consuming and the mulcher uses fossil fuels (but I could probably run it from a solar panel). Pea straw and sugar cane have to be transported to the retailer and then home from there. Sugar cane probably comes from Queensland (I’m in Victoria), a considerable distance. More fossil fuels. I have no idea where the pea straw comes from. It could be Victoria or interstate. More fossil fuels anyway. Sugar cane is compressed and neatly bundled in a plastic bale which I can just manage to lift (plastic’s a no-no, though) and which doesn’t mess up my car. Pea straw is compressed and tied, sheds bits all over the back of the car and is heavy and awkward to manage.

Aesthetics: Bracken is green when first mulched and applied but soon goes brown in the sun. It looks attractive (at least to me!) and doesn’t pack down with heavy rain. Pea straw and sugar cane look good as well, but the sugar cane tends to pack down with rain and needs to be lightly fluffed up with a fork. I do like the look of pea straw, though. Nothing makes a permaculture garden look more like a permaculture garden than a nice fluffy layer of fresh pea straw. It doesn’t start to really pack down until it’s been softened by rain and partially rotted.

Application: No problems with the bracken. The pea straw comes in long stringy bits and needs to be teased out of the bale. If it’s dry it can be a bit dusty but not as much as the sugar cane which is very dry and dusty to put down. I find it’s best to remove the plastic covering completely and leave the bale out in the rain or give it a bit of a sprinkle with the hose. Once it’s damp it softens and is easier (and safer on the lungs) to apply.

Rottability: Bracken takes the longest time to break down although when it does it adds potassium to the soil, as it is said to be rich in this element. I expect the pea straw will add nitrogen to the soil, but I have no information on what nutrients sugar cane will add. It can be lightly forked into the soil, increasing the organic matter and will start to break down fairly readily. Pea straw takes a bit longer to break down.

Extra bonus: From the pea straw only, as it usually contains a liberal sprinkling of dried peas and will produce a useful crop if left to do so.

Chemicals: Bracken is growing naturally, so it’s organic. The label on the bale of sugar cane claims it’s organic, too. No info on the pea straw. It’s likely to have been grown with chemicals and treated with pesticides.

Summing up: As you can see, all three mulches have pros and cons, but for me, the sugar cane mulch wins by a short half-head because of the way it quickly adds organic matter to the soil and increases it’s water-holding capacity. I’ve also put a layer of it on top of all three of my compost bins and now that we’re getting rain and it’s softening, the worms are coming up underneath it, helping to break it down and incorporate it into the compost. If I lightly fork it in and add another layer and continue to do this, it’s producing a beautiful rich friable compost, all of which will be going into my water-wicking boxes this summer.