CHENNAI: A major scientific study published in the international journal Scientific Reports has raised fresh concerns over the ecological sustainability of farming practices in the Nilgiris, warning that decades-old land assessment systems have dangerously underestimated the impact of erosion in the fragile hill ecosystem while misjudging the region’s true agricultural potential.
The study, carried out by scientists from the ICAR-Indian Institute of Soil and Water Conservation (IISWC), Dehradun, the IISWC Research Centre at Udhagamandalam, University of Nebraska-Lincoln in the US, ICAR-CPCRI Krishi Vigyan Kendra in Kerala and the International Water Management Institute (IWMI), New Delhi, has proposed a new ‘Erosion Hazard Index’ tailored specifically for the Nilgiris terrain.
The research was led by DV Singh, M Madhu, Sheetal K Radhakrishnan, Devideen Yadav, P Muralidharan, PS Renjith and AK Sikka focused on the Thambatti watershed near Udhagamandalam in the district. They said that the new model was developed after existing land suitability systems classified vast stretches of The Nilgiris as unsuitable for crops such as potato, cauliflower, beans and wheat despite these crops having been cultivated in the hills for generations.
Conventional frameworks relied heavily on slope measurements while overlooking how local farmers have historically reduced erosion risks through terracing and hill-based conservation methods
The study said conventional frameworks, mostly adapted from plains agriculture, relied heavily on slope measurements while overlooking how local farmers have historically reduced erosion risks through terracing and hill-based conservation methods. “A steep slope protected by well-maintained terraces behaves fundamentally differently from an unprotected cultivated slope,” the researchers noted. “Land management practices must be treated as a core component of agricultural suitability in mountain ecosystems.”
Conducted across a 522-hectare watershed located about 12 km from Udhagamandalam town, the study covered elevations ranging between 1,950 and 2,390 metres above sea level. The region receives an average annual rainfall of 139 cm and is dominated by tea plantations and vegetable cultivation.
Researchers used extensive field surveys, laboratory soil analysis and climatic data collected over 20 years between 2004 and 2023 to develop the revised model. Around 177 farmers from 407 families in the watershed were interviewed to document cultivation patterns, slope conditions, terrace systems and land management practices.
Soil pH levels in the study area ranged between 3.9 and 5.62, conditions that restrict nutrient availability and reduce suitability for several annual crops
Erosion Hazard Index combines slope steepness and land management conditions into a single parameter to determine whether land can sustain cultivation without accelerating degradation. The study found tea to be the most ecologically compatible crop for The Nilgiris landscape due to its deep-rooted perennial canopy, tolerance to acidic soils and relatively greater resistance to erosion.
According to the findings, 37.4% of the watershed was classified as highly suitable for tea cultivation, while another 44.4% was moderately suitable, taking the total suitable area for tea to 81.8%.
The report said annual vegetable crops such as potato, cabbage, cauliflower, broccoli, carrot and radish face severe limitations because of erosion hazards associated with steep slopes and inadequate conservation measures. Only 6.9% of the watershed was found to be highly suitable for potato cultivation, while nearly 64% was categorised as unsuitable.
The study observed that annual crops are especially vulnerable in hill regions because repeated soil disturbance, shallow rooting systems and exposed surfaces during rainfall periods significantly increase erosion risks. Field beans were found to suffer mainly because of high soil acidity across the Nilgiris. Researchers said no highly suitable land could be identified for field bean cultivation within the study area.
Wheat emerged as the least suitable crop assessed in the study. No highly suitable land for wheat cultivation was identified, while over 70% of the watershed was categorised as unsuitable due to temperature constraints and erosion sensitivity.
The report also identified soil acidity as a defining agricultural challenge in the Nilgiris. Soil pH levels in the study area ranged between 3.9 and 5.62, conditions that restrict nutrient availability and reduce suitability for several annual crops.
Researchers cautioned that continued expansion of annual crop cultivation into steep hill slopes without adequate conservation systems could intensify land degradation and ecological instability in the Western Ghats. Calling for a shift towards erosion-sensitive agricultural planning, the study recommended crop zoning based on terrain stability, climatic suitability and long-term sustainability rather than relying on generic national land classification standards.
Researchers say existing FAO-based land assessment models failed to reflect realities of hill farming
Crops like potato, cauliflower and beans ‘unsuitable despite decades of successful cultivation
Study covered the 522-hectare Thambatti watershed near Udhagamandalam
Field surveys, soil analysis and climatic data collected between 2004 and 2023
177 farmers from 407 families surveyed to document cultivation and conservation practices
Tea most ecologically stable crop for the terrain due to deep root systems, canopy cover and tolerance to acidic soils
Annual vegetable crops highly vulnerable to erosion on steep slopes
Nearly two-thirds of watershed unsuitable for potato cultivation
Wheat least suitable crop due to temperature, erosion limitations