9 Benchmark Soils in Agro-ecological Regions K. S. Anil Kumar, K. S. Karthika, M. Lalitha, R. Srinivasan, Shivanand, K. Sujatha, K. M. Nair, R. Hegde, S. K. Singh, and Bipin B. Mishra Abstract The benchmark soils in twenty agro-ecological regions of the country are briefly explained in this chapter using the established soil series to interpret soils, their physical, chemical characteristics, problems and potentials. This would be helpful in identifying the use of soil resource inventory and classification in optimal land use and production system. In fact, a benchmark soil is widely extensive, holds a key position in the soil classification system and is of special significance to farming, engineering or other uses and focuses on its agronomic concepts for wider acceptability of interpretations and for extrapolation of research data. It is representative of the most extensive soils in major land resource area or agro-ecological zone. This chapter highlights the benchmark soils in conducting soil correlation, standard- ization of legends, prediction of soil behaviour, agro-technology transfer and planning for further research in soil science and allied disciplines. However, further refinement in its applications using GIS tools is of priority. Keywords Benchmark soils Á Agro-ecological regions Á Soil series Á Soil classification Á Resource inventory Á Agro-technology transfer 9.1 Introduction India is gifted with a variety of soils due to varying geo- logical formations, diversified climate, topography and relief. Such diversifications have given rise to varied phys- iographic features. This extends from the snow-clad moun- tainous peaks, thick forests in the north, to the lengthy coasts in the Peninsula. The temperature varies from arctic cold to equatorial hot, and rainfall varies from few centimetres in the arid regions to per-humid regions with maximum rainfall of several hundred centimetres per annum. These variations in temperature and rainfall have provided for high plateaus, hills, valleys, rolling uplands, swampy lowlands, fertile plains and barren deserts. These varied natural environments have resulted in a large variety of soils distinctly different from one another creating soil as a valuable resource of India. Eighty-two benchmark soils have been identified in the 27 different major land resource areas of Kerala for which soil monoliths were collected (GOI 2019). According to USDA (2017), a benchmark soil is one of large extent within one or more major land resource areas (MLRAs), one that holds a key position in the soil classifi- cation system, one for which there is a large amount of data, one that has special importance to one or more significant land uses or one that is of significant ecological importance. Benchmark soils, while being important soils in their own right, are also intended to serve as proxies for other similar soils. Their purpose is to focus on data collection and the investigative effort on soils that have the greatest potential for extending collected data and resultant interpretations to other soils. In fact, this purpose is relevant both in making soil surveys and to soil survey customers in their goal to extend findings of their research. The cost of investigation and the large number of combinations of soil uses and management practices preclude laboratory and field studies of all soils; therefore, studies of benchmark soils are an essential com- ponent of developing nationwide soil databases and soil interpretations. Data obtained by studying benchmark soils K. S. Anil Kumar (&) Á K. S. Karthika Á M. Lalitha Á R. Srinivasan Á Shivanand Á K. Sujatha Á K. M. Nair Á R. Hegde ICAR-National Bureau of Soil Survey and Land Use Planning, Regional Centre, Hebbal, Bangalore 560024, India e-mail: anilsoils@yahoo.co.in S. K. Singh ICAR-National Bureau of Soil Survey and Land Use Planning, Amravati Road, University P.O., Nagpur 440033, India B. B. Mishra Bihar Agricultural University, Sabour, Bhagalpur 813210, India Pedology and Land Use Planning, School of Natural Resources Management and Environmental Sciences, Haramaya University, P O Box 138 Dire Dawa, Ethiopia International Union of Soil Science, Vienna, Austria © Springer Nature Switzerland AG 2020 B. B. Mishra (ed.), The Soils of India, World Soils Book Series, https://doi.org/10.1007/978-3-030-31082-0_9 159