I often have my camera pointed to the ground here because I’m attracted to the colour. The soil has a lot of iron in it and that’s what gives it its red colour. A Lao friend saw this photo and said she hated it because it reminded her of how dirty red soil is when it's wet. Even during the dry season it's dirty enough...you can write your name in the red dust which attaches itself to car windows, I have to wipe down the clothes dryer every time I use it because of the build up of reddish grime and my feet turn red when I've been out walking. So, red soil has been on my mind recently and I've learned a bit in the process.
Red soil develops in a warm, damp climate under layers of vegetation. If it’s worked over well, fertilized and irrigated crop yields will be high. Suitable crops for the soil include rice, corn and sugar cane. One of the names soil scientists use when talking about red soil is acrisol.
Soil fertility refers to whether or not it is easy to grow crops. Soil stability is a function of soil structure and includes the ability of the soil to reduce erosion, improve filtration and store water as well as the ease with which plant roots penetrate the soil. Water holding capacity refers to the ability of the soil to contain and retain water. Soil percolation is about the soil’s ability to drain water. Soil fauna are both beneficial and harmful organisms which aid or hinder decomposition and improve or destroy soil structure.
Red soil is an acrisol and characterized by low fertility, low stability, low water holding ability, low fauna activity and slow drainage. Slow drainage can result in stagnation and that in turn creates a breeding site for mosquitoes which carry malaria and dengue.
According to this chart, https://tinyurl.com/soils-of-South-East-Asia, nearly 163,000 square kilometres or more than 70% of Laos is characterized by acrisols. That figure is higher than for any other country in mainland Southeast Asia (MSEA). Most of MSEA is composed of acrisols. Acrisols occupy just under 8% of the earth’s surface.
Red soil can be remediated of course through the use of fertilizers. David Montgomery from the University of Washington https://tinyurl.com/healthy-soil-is-key argues that the key to sustainable agriculture involves rebuilding soils so that conventional small-scale farming becomes the normal way to feed people. You’ve already read or heard about the billions of kilos of food we throw away each year in the West and that a quarter of what the West produces is never consumed. Maybe if we had to grow some of our own food we would stop consigning perfectly good food to the rubbish bins. Maybe we’d understand how much work is undertaken by subsistence farmers especially in the developing countries of Southeast Asia and we’d recognize that “shifting cultivation” aka “slash and burn” is no solution.
At Bang Chan village near Luang Prabang in the north of Laos, the potters have prized the high clay content of red soil for centuries. The village is renowned for its pots, roof tiles and bricks which can be seen throughout Luang Prabang.
The heavy rainfall and intense heat in MSEA combine with the red soil to produce laterite, the easily quarried stone used in the construction of the Angkorian temples of Cambodia, Laos and Thailand. During the French colonial period in Southeast Asia, crushed laterite was also an important material for the construction of roads. Our guide at Angkor Wat explained that the French had also dismantled temples in order to build those roads.