Current evidence suggests that Indigenous farmers in the North American Southwest began canal irrigation in the second millennium BC, marking an important change in food production technology. Early canal systems are preserved in alluvial floodplains of the US-Mexico Borderlands region, tend to be deeply buried, and can appear as natural fluvial features. Here I discuss some of the challenges in identifying early canals and associated fields and present case studies from the Santa Cruz River in southern Arizona where buried channels dating as early as 1600–1400 BC were likely human constructed. These small channels share several stratigraphic properties and are consistent with hypotheses of early canal irrigation practiced by small family groups reliant on mixed farming and foraging. Through time, irrigation canal systems expanded in size, resulting in increased labor investment, sedentism, and productivity and facilitating the development of larger irrigation communities. Stratigraphic and geomorphic properties of early canal systems thus far identified along the Santa Cruz River provide a framework for identifying potential early canal evidence in other fine-grained floodplains of the Southwest, thereby improving our understanding of Indigenous agricultural intensification.

In north-central China, subsistence practices transitioned from hunting and gathering to millet-based agriculture between the early and middle Holocene. To better understand how ancient environmental changes influenced this shift in subsistence strategies and human activities at regional to local levels, we conducted palynological and lithologic analyses on radiocarbon-dated sediment cores from the Luoyang Basin, western Henan Province. Our palynological results suggest that vegetation shifted from broad-leaved deciduous forest (9230–8850 cal yr BP) to steppe-meadow vegetation (8850–7550 cal yr BP), and then to steppe with sparse trees (7550–6920 cal yr BP). Lithologic analyses also indicate that the stabilization of the Luoyang Basin’s floodplain after ~8370 cal yr BP might have attracted people to move into the basin, promoting the emergence of millet-based agriculture during the Peiligang culture period (8500–7000 cal yr BP). Once agricultural practices emerged, the climatic optimum after ~7550 cal yr BP likely facilitated the expansion of the Yangshao culture (7000–5000 cal yr BP) in north-central China. As agriculture intensified, pollen taxa related to human disturbance, such as Urtica, increased in abundance.

Current knowledge of the beginnings of crop cultivation in Lithuania is based mainly on Cerealia-type pollen data supplemented by other indirect evidence such as agricultural tools. We argue that these records, predating carbonized remains of cultivated plants, are not substantial enough indicators of the early stages of agriculture in Lithuania. Here, we demonstrate that the macroremains of cultural plants that were previously reported from two Neolithic settlements in Lithuania were either mistakenly identified as domestic crops or incorrectly ascribed to the Neolithic period due to movement through the stratigraphic sequence and the absence of direct dating of cereal grains. Furthermore, we present a charred Hordeum vulgare grain from the Bronze Age settlement of Kvietiniai in western Lithuania. It was AMS-dated to 1392–1123 cal bc, and at present represents the earliest definite evidence for a crop in the eastern Baltic region. We conclude that, presently, there are no grounds to suggest that crop cultivation took place in Lithuania during the Neolithic.

Agricultural research conducted in the United States since establishment of the U.S. Dept. of Agriculture and Land-Grant University System in 1862 has shown that regular and proper additions of organic materials are very important for maintaining the tilth, fertility, and productivity of agricultural soils, protecting them from wind and water erosion, and preventing nutrient losses by runoff and leaching. Several millennia earlier, Roman agriculturists were advocating crop rotations, green manuring, composts, legumes, farmyard manures, crop residues, wood ashes, seaweed, and sewage wastes for supplying humus and nutrients to restore or enhance soil productivity. Even earlier, Asian farmers also used these practices to maintain healthy and productive soils. Today the most serious problem in U.S. agriculture and agriculture worldwide is the widespread degradation of agricultural soils through erosion and the consequential decline in productivity. In view of how much information is available on the benefits of organic recycling on agricultural lands, one wonders why we aren't doing a better job of protecting and conserving our land resource base. We discuss strategies for using organic resources more effectively to achieve a more sustainable agriculture for the future.