Mulch or compost?

When I first arrived in Perth in 1978 I thought someone had dumped a load of sand in the backyard. And indeed the load went down a long way. Great for drainage but this meant any added nutrients left quickly too. Combined with an increasingly longer, drier summer we must act to improve conditions. Organic material must be added if we want to grow food. The soil is lifeless, in the true sense of having very little microbial activity. Artificial fertilisers will provide all the chemicals required but only feed the plant directly next to the application site. When we add organic material, microbes such as fungi and bacteria, worms and more start to work. They breakdown the material and carry it around the soil making the nutrients available but also assisting in improving the water holding capacity of the soil. Lifeless soil becomes teeming with activity.

An additional step if we live in the sandy bits is to add some clay. This will help to hold the nutrients in the soil and not be responsible for adding extra nutrient load to our groundwater and waterways. Soil wetting agents will be important to keep the waxy (water repellent) layer accumulating around organic material too. Beyond Gardens assist with seminars and e learning on how to get the best from Perth soils according to our needs.

So do we need mulch or compost? Is there a difference and what method is best? Mulch is big stuff like barks, wood chips and straw, mostly the dry brown carbon rich materials. Compost is the fine broken down material full of microbes ready to feed the plant the nutrients from broken down organic material. Mulch will become compost eventually, but its initial task is help reduce evaporation, keep the soil a more even temperature, and protect the compost layer from radiation (too much sun)

In a forest the mulch is generated by the falling leaves and branches. In the contrived environment of a suburban landscape we tend to prune the plants, sweep the leaves and put them all in ‘the bin’ (albeit the green waste bin). To mulch and compost the area we then purchase the mulch and compost to cover and enrich the ground. I suggest we need to imitate the forest more. Keep the prunings and leaves, there are plenty around if you don’t have enough just ask your neighbors or tap the lawn mowing contractor on the shoulder. We can process these ourselves and harvest the rewards. We don’t have enough space for a compost bin? There are alternatives such as worm farms or bokashi buckets;- or just bury it all!

The kind of mulch we use can depend on what is available. Back to the forest- is it local and free. Residents can utilise a free service called Mulchnet  whereby treeloppers provide truckloads of mulch to save offloading somewhere else. This delivery of local quality material was the genius idea of  Tim Lawrence.

As mulch will eventually breakdown to become compost we can just mulch. However to speed the soil enrichment process up if we add compost it should be dug in or cover with mulch to preserve the bacterial life within. There is plenty of material for compost around us. Half of our general waste is organic, if it was alive once we can compost it. To bulk up the content there are leaves in the gutter, grass clippings from the contractors, coffee grounds from the cafes, scraps from the markets, shredded paper from the office. Think not of ‘waste’ but ‘wasted resources’ and the financial cost of adding nutrients to your soil will be minimal.