Agricultural resilience and land-use from an Indus settlement in north-western India: Inferences from stable Carbon and Nitrogen isotopes of archaeobotanical remains

Abstract

Stable isotopic compositions of carbon and nitrogen (δ 13 C, δ 15 N) of archaeological grains/seeds recovered from different cultural layers of an Indus archaeological site 4MSR (29°12'87.2"N; 73°9'421"E; Binjor, western Rajasthan, India) provide insights into the Harappan agriculture between ~ 2900 to ~ 1800 BCE. While δ 13 C values were used to retrieve hydrological status, δ 15 N values were used to gauge agricultural intensi cation. Isotopic data of grains/seeds were generated representing three Indus phases (i) early phase (~ 2900 − 2600 BCE), (ii) transitional phase (~ 2600 − 2500 BCE) and (iii) mature phase (~ 2500 − 1800 BCE). We nd δ 13 C values of barley grains (winter crop) varied in overlapping ranges for all the three phases − 21.3‰±1.9; −22.9‰±1.6 and − 22.7‰±1.7 respectively (n = 10 for each phase) indicating insigni cant changes in hydrology for winter crops. For summer crops cotton also, average δ 13 C values for transitional phase − 23.7‰±1.8 were not signi cantly different from those of mature phase − 22.5‰±2.4. δ 15 N barley values also varied in wider ranges, however, intra-phase variability appears to have progressively increased from early (8.0‰±1.7) to transitional phase (7.3‰±2.5) and then mature phase (9.2‰±7.2) indicating a plausible agricultural intensi cation. We also measured δ 13 C of host soil organic matter (SOM) and sediment δ 15 N to assess regional environmental conditions. In contrast to the trends observed for archaeological grains, δ 13 C SOM values showed a statistically signi cant enriching trend from early (−23.6‰±1.4) to mature phase (−20.3‰±1.9) hinting a growing aridity in the region. We surmise that Harappan farmers of western Rajasthan region might be managing arable hydrological conditions in their elds through agricultural interventions to continue agriculture practices despite growing aridity in the vicinity.