- A recent study documents a relatively remote site in northeast India, where the traditional “shifting cultivation” form of agriculture is still practised by the local Adi community.
- The study offers a different and more holistic perspective on this age-old agricultural form which is often considered unsustainable and ecologically harmful.
- Ethnopedological information like in the study can be useful for policy making and soil management that can be replicated in other sites with similar soil constraints.
A new study highlights a different perspective on the age-old practice of “shifting cultivation” – an agricultural form considered unsustainable and ecologically harmful. Documenting the knowledge of an indigenous community in northeast India, the study highlights how traditional cultivators manage issues of soil erosion and fertility.
Shifting cultivation or jhum is an agricultural system where a patch of forest is cleared, cultivated upon for a couple of years and then left fallow for the soil to recover its nutrients and the trees to grow back.
This form of agriculture is practised by native communities all across the tropics, from South America to Africa to South-East Asia. About half a million families in northeast India practise jhum, over an area of roughly half a million hectares (5,000 square kilometres).
As shifting cultivation involves clearing forests, the practice is often considered ecologically harmful. “It is looked at as a deforestation activity,” said Karthik Teegalapalli, researcher at the National Centre for Biological Sciences (NCBS), Bengaluru, who studies shifting cultivation. It is also regarded that shifting cultivation leads to loss of soil fertility, erosion and soil runoff. According to Teegalapalli, “instead of looking at the larger picture, soil researchers tend to look at the deforestation part of it or clearing part – which is only one aspect of shifting cultivation.”
In a recent study, Teegalapalli and his colleagues report the poorly studied aspects of jhum. The team documents how soil recovers its nutrients after a forest patch has been cleared for agriculture. The researchers also chronicle the traditional knowledge of the Adi community in Upper Siang district of Arunachal Pradesh in northeast India.
“The farmers of the Adi community, like many shifting cultivators, show a good understanding of their landscape and manage their farms accordingly,” said Deborah Lawrence, co-author on this study and a professor in the department of Environmental Sciences at the University of Virginia in the United States.
The study found that patches that lie fallow for several years have higher pools of nitrogen and phosphorous, elements that are crucial for successful development of crops. The study also found organic matter in the soil of the oldest fallow is not significantly different to that found in uncut forests. “These results indicate that long-fallow shifting cultivation can be sustainable,” said Lawrence.
Amit Kurien, a researcher at the Ashoka Trust for Research in Ecology and the Environment (ATREE), said “the interesting aspect about this study is that it highlights that shifting cultivation farmers have elaborate agricultural knowledge systems and land management techniques.” Kurien was not involved in the study.
Lessons from the locals
The Adi people form the most populous clan in Arunachal Pradesh and are spread across the Lower Dibang valley, East, West and Upper Siang districts. They have been almost entirely dependent on hunting and jhum with long fallow periods, for centuries. Often, many households together carry out the clearing and cultivation. “Socially this keeps the people together, they help each other out and festivals are observed around shifting cultivation,” said Teegalapalli. This togetherness also lends more bodies to guard against animals invading their crops.
To document the soil knowledge of the Adi community, Teegalapalli interviewed experienced farmers of Bomdo village in the Upper Siang. He solicited information on soil types, colour and texture, local nomenclature for these soils, different areas where differing soils occur, preferred areas for cultivation and various crops grown.
The Adi people are spread across the Lower Dibang valley, East, West and Upper Siang districts. Image created on Google Maps.
Teegalapalli collected three soil samples each from sites left fallow for 3, 12 and 25 years. He also collected samples from a patch currently under cultivation as well as from an uncut forest. From each of these sites, he amassed the topsoil layer from twenty different points on a particular farm.
The researchers estimated levels of nitrogen, phosphorous, potassium and soil organic carbon in the samples, at the laboratory in the College of Horticulture and Forestry in East Siang district.
The researchers found that nitrogen, phosphorus and organic matter are correlated to the age of a site. “Organic matter, phosphorus, and nitrogen, all three, have a tendency to increase with age,” said Teegalapalli. In uncut forests, the contents are at a maximum. “But as you go to younger sites these will reduce in content.”
The way this cycle runs is, initially, when a patch of forest is cleared and burnt, the nutrients in the soil increase, as ash from woody plants gets deposited. But then, as the crops grow, the nutrients are utilised by the crops and reduce in the soil. The depleted nutrients are then replenished in the soil as trees grow back during the fallow years.
“The trees are able to mine the deeper soils, through deep roots and bring additional nutrients into the root zone of the cropping system,” said co-author Lawrence. “Trees are a bank for nutrients, accumulating them over time until farmers are ready to withdraw some for another set of crops.”
They also help the soil to absorb water, preventing soil and nutrient runoff.
From their study sites, the researchers found that organic content, nitrogen and phosphorus was at 80, 79 and 68 percent respectively in recently cultivated patches after forests were cut. These increased to 90, 84 and 89 percent after a twelve year fallow period. Most farmers in this region leave their lands fallow for ten years. “Our study, however, suggests that the ideal fallow period is somewhere between 12 and 25 years rather than the 10 years currently being practiced,” said Lawrence.
Leaving land for long fallow periods is an integral part of traditional shifting cultivation. As this practice is a few centuries old, it involves knowledge and management of local soils. A 2003 study describes ‘ethnopedology’ as a field of study to “document and understand local approaches to soil perception, classification, appraisal, use and management”.
Teegalapalli and his collaborators documented the ethnopedological knowledge of the Adi community. They found that Adi people identify nine types of soils and plant crops according to the properties of the soil.
“Their knowledge is far more nuanced because their concern appears to be not just the field they cultivate, but also the surroundings,” said Kurien of ATREE. “Plus, they also grow a vast diversity of crops.”
Rice and millets are the staple crops but the Adi people seem to know what crops to plant if a field adjoins a forest and other agricultural plots. Beans, taro (a variety of colocasia) and brinjal are planted on boundaries when a farm adjoins another field. If the farm is next to a forest patch, pumpkin and varieties of long beans are grown as Adi people believe they deplete the fertility of the soil.
“For me this was surprising because it shows Adis know what kind of crops take up what kind of nutrients and how it affects other crops,” said Teegalapalli.
The Adi people also make use of objects like rocks and logs that can be found on a farm. Corn and a variety of spring onions are planted along fallen logs. Chillies are grown near rocks. “These are signs of well-evolved knowledge systems and a highly knowledgeable farming community, rather contrary to what official policy on shifting cultivation states,” said Kurien.
Jhum has for long been considered as environmentally damaging. “The British said it was a wasteful practice,” said Teegalapalli. “The same hangover has persisted in India post independence.” In recent times many state governments in northeast India have actively discouraged jhum and have instead promoted settled, monoculture plantations of palm and rubber.
But as this study shows that if done in a systematic manner, as the Adi community does, jhum not only benefits the soils but also lets a community manage their landscape. Such traditional practices may perhaps come in handy to combat challenges like climate change and forest loss.
Teegalapalli K., Mailappa S A., Lyngdoh N., Lawrence D. (2018) Recovery of soil macronutrients following shifting cultivation and ethnopedology of the Adi community in the Eastern Himalaya. Soil Use and Management. https://doi.org/10.1111/sum.12420