My thoughts exactly, pingdong. It’s a crying shame they treat waste as waste and not as a valuable resource; sure, there’s a bit of food-reuse going on (for example) but as you say, agricultural waste is often burned, and just because their plots are small doesn’t mean they’re using less chemicals.
I think the main issue is that they’re using techniques that were developed for temperate-climate agriculture. They don’t work very well there (soil erosion etc) but in a semi-tropical climate, they’re utterly disastrous because everything happens three or four times as fast and the weather is a lot less forgiving. I was reading a paper the other day written by a Brazilian researcher: their conclusion is that in the tropics, on poor soils, most plants actually grow in (take root in) the humus layer, not in the earth. Phosphorus and micronutrients are “mined” by various helper species (trees, generally), which then decay and introduce those nutrients in a more bioavailable form to the topsoil. No humus layer, no growth.
On my plot, I slashed down the undergrowth, nailed down some cardboard and newspaper, and scattered a bit of earth and random garbage over the top. I’ve now got various legumes sprouting through holes punched in the cardboard, which, together with the slash, has turned into dark, rich compost in six months. The weeds have virtually disappeared, except on an area that I left purposely uncovered to see what would happen. I love this climate!