Agricultural extensification or intensification: Nitrogen isotopic investigation into late Yangshao agricultural strategies in the middle Yellow River area

Abstract

Millet-dominant agriculture built a solid material base for cultural expansion and social development in prehistoric northern China. Around the middle-late Yangshao period (around 4000 BCE–2600 BCE), especially during the late Yangshao period (around 3500 BCE–2600 BCE), with the establishment of settlement hierarchies and population growth in the middle Yellow River area, response patterns of settlements in this area mainly focused on strategies to increase crop yields and food supplies. Response patterns included agricultural intensification (increasing inputs of labor and resources) and agricultural extensification (significant expansion of the land under cultivation). To date, the detailed farming strategies in the different regions of this area have not yet been clearly illustrated. Our study reports on the new isotopic data of charred seeds (crops and weeds) from archaeological sites in the Zhengzhou region, and investigates the crop management practices based on elevated nitrogen isotope values (e.g., δ15N) in crops to elucidate agricultural strategies during the late Yangshao period (around 3500 BCE–2600 BCE) in the middle Yellow River area by combining the new data with previous interdisciplinary studies.Elevated nitrogen isotope values of cereal grains relative to local vegetation indicates that crops were likely manured in Zhengzhou region. Manuring practices possibly prevailed in the middle Yellow River area during the late Yangshao period, although the amount of manuring varied likely due to topographical conditions. A combined agricultural strategy of intensification (mixed crop cultivation/manuring) and extensification (expansion of the land under cultivation) was likely employed in the center settlement of Dahecun to feed the inhabitants and ensure the development of the settlement. Due to limited available land for cultivation and pure millet cultivation, increasing crop yields with manuring formed an essential part of the agricultural strategy in the Baishui River area. This indicates that agricultural intensification was likely the most effective avenue to support growing populations and land demand in the regional center Xiahe and other sites in Baishui River area. Faced with societal development and different environmental conditions, settlements in the different regions in the middle Yellow River area likely adopted their own agricultural strategies in response to internal and external conditions, indicating late Yangshao settlement resilience in this area.