This article is a re-post from 2014, but is especially relevant given Colombo’s weather this week
I see it everywhere. Naked soil when now is the time to add more mulch.
This is not a great situation in any climate, but especially not here in the tropics. The rains are beating down and the mud is splashing. The precious nutrients in your soil are being lost by the second. These torrential downpours are the biggest cause of nutrient loss in tropical soils and the only things you can do about it are to allow plants to take root and slow the flow manually. Easier than large earthworks like swales and dams, mulch is a great way to hold on to nutrients and protect your soil through the monsoon seasons.
Now is the time for coppicing and dropping large pieces of woody mulch around your trees, perennial crops, and empty vegetable beds. The rain is a quick composter, so larger pieces are better suited to feeding the soil throughout the season. Smaller mulches will breakdown too quickly and their nutrients will wash away before plants can make use of them. Good mulches will be your hedgerow nitrogen trees, banana logs, coconut husks, palm fronds, and timber thinning.
You should also be making the most of the rains to grow green mulches. Amaranth, cowpea, and other nitrogen-fixing crops will help to hold the soil and mine nutrients for your use in the next season with crops that like drier conditions. Temperate climate gardeners are accustomed to periods of dormancy in the soil, but the tropics work differently. We can give a garden plot a break from being worked, but it will never really go dormant. The soil must be covered at all times and nature will plant something. If you prefer to see growth you can make multiple uses of, plant your green mulches. This will ultimately help to prevent nutrient loss, build healthy topsoil, and prevent weeds that can make the plot difficult to work with in the future.
Don’t forget the pots!
Even those of us growing in pots and planters on the roof have to be prudent about mulching. Our little growing spaces see more of the extremes in weather. One day the rains are beating carefully collected soil out of the pots and the next day the sun is doing its best to dry everything out, making no distinction between puddles and plants. We might not have the advantage of hedgerow and tree crops to borrow from, but there are many materials we can find around our homes and communities.
Make use of everything. The other day I cut up my husband’s worn-out cotton underwear for mulch. Most of our in-coming cardboard and paper end up as mulch as well. Any leaf sweepings and neighboring tree limbs threatening our gutters are also chopped and tucked in the beds and pots. If it can be composted, it can serve as a mulch during the monsoons. Just be sure to leave space around your trees and plant stems so that they are not burnt by the decomposition.
Why not apply compost?
Simply, it washes away too easily. We are still composting throughout the monsoon season by mixing our food scraps in with the large mulch we put down, but we only really apply finished compost to the pots and beds once the rains stop. Otherwise it washes out so quickly it provides no real benefit to the soil. Once the rains end I will be writing more about the benefits of finished compost to help get us through the dry season. Until then, mulch and larger food scraps breakdown slowly with the rain so the soil is protected and still being fed.