Construction and Agriculture in Sand at the Early Islamic Plot-and-Berm Groundwater Harvesting Agroecosystem South of Ancient Caesarea

Based on surveys and three excavation seasons, we report details on one of the first major utilizations of loose aeolian sand for construction and (hypothesized) vegetable agriculture at the Early Islamic Plot-and-Berm (P&B) agroecosystem south of Caesarea Maritima, along the Mediterranean coast of Israel. P&B agroecosystems are an innovative initiative to reconstruct sand bodies and dunefields into agricultural plots sunken between sand berms. These agroecosystems are sporadically found between Iran and Iberia and some are still in use. The plots, usually ~1 m above the groundwater table allowed easy access to the water via shallow wells for irrigation.

Research methods included pedological and sedimentological analyses, micromorphology and compositional analyses such as Fourier Transform Infrared Spectroscopy to detect heating of cultural additives (e.g., fired clays, pyrogenic lime); plant ashes (e.g., deliberate enrichment of fuel and/or recycling of former crop cycles as part of plot maintenance); and pollen and phytolith analysis to detect micro-botanical proxies of crops. Relative chronologies were obtained from portable luminescence profiling (pOSL). OSL ages along with artifacts analysis indicate that the agroecosystem was established during the late 9^th or 10^th century and functioning until the early decades of the 12^th.

Refuse, including ash, carbonate, trace elements and artifacts, extracted from the dumps of Caesarea was combined with local sand to stabilize the berm surface but also partly altered the physical and chemical properties of the sand and increased its fertility, mainly in the plots, to form grey sandy to sandy loam anthrosols. This refuse was combined in different mixtures along the ~5 m thick berm fill and upon its slope and crest surface to stabilize the earthwork and comprise an anti-erosive agent. Similar mixtures were used to support berms and foundations of structures that served for lime production, agroecosystem management and local farming utilities. A 5 m high mound constructed out of interchanging anthrosediments was also piled up within a plot to support a presumable guarding structure. 

Plot anthrosols appear to include a basal, dark grey 20-40 m thick unit, ~ 1 m above the groundwater table that was enrichened with carbonate overlaid by a ~1 m thick grey sand anthrosol. The lower unit probably served for preserving infiltrating irrigation water that was applied to the crops grown atop the light grey anthrosol.

The agroecosystem remained well-preserved and untouched until the mid-20th century. Its pristine preservation is evidence of the ingenious and widespread utilization of refuse for construction and agriculture in sand. The untouched shape of this agrotechnological earthwork in the last millennia is intriguing and may be due to either lack of knowledge, or resources per revenue for similar endeavors.