PERSPECTIVAS DE LA PRODUCCIÓN PRIMARIA EN EL

The parent material of the soils in the Belize River valley is primarily limestone- derived, a result of the weathering and erosion of the Maya Mountains. In the Late Pleistocene, the current Belize River and much of present-day northern Belize was a shallow bay to the north of the Maya Mountains (Fedick 1994, 1995). Over time, the erosion of the Cretaceous limestone cap on the uplands filled the bay with limestone rubble and sand. The parent material of the soils in the Belize River valley, then, is this Cretaceous limestone brought down from the erosion of the uplands of the Maya Mountains. Although the Belize River valley was once part of the ancient coastline and held a great deal of sand and quartz-rich coastal sediments, these have since eroded away. However, the silica-rich sediments brought down from the Maya Mountains may have created many chert beds throughout the area (Fedick 1994).

Much of the soils in the Belize River valley are therefore primarily created from a limestone substrate (although the soils along the river terraces are more clay-rich soil created from alluvial sediments), and limestone-derived soils can be very productive for agriculture (Wright et al. 1959). However, as the topography is karstic, with rolling hills, towers, cliffs, and sinkholes, the soils on hilltops, hillslopes, and low-lying areas can be quite different from each other. In the low-lying areas as well as on the river terraces

along the Belize River, clays tend to accumulate, presenting drainage problems and making maize cultivation difficult (Wright et al. 1959). This finding prompted Willey (1965) to suggest that the river terraces were utilized primarily for settlement and the cultivation of root crops and cacao, with maize agriculture practiced on the nearby hillslopes. Fedick (1989), however, questioned this characterization of river terrace soils, pointing out that subsequent research has identified them as some of the most fertile in the area.

The Belize River valley contains both highly acidic and alkaline soils, with an average pH in the region of 6.4, indicating the soils are neutral to slightly acidic (Kellman 1973). Soil pH greatly impacts the types of plants that can be grown as well as the soil fertility. Some plants will not thrive in soils that are too acidic or alkaline and require human intervention to remain productive. Domesticates such as manioc will tolerate nutrient poor acidic soils as long as the soils are well-drained, while maize thrives in environments with neutral pH and requires soils rich in nutrients (Roosevelt 1980).

The rugged upland terrain of the Belize River valley includes enclosed depressions and residual hills, with gray and brown soils of the Toledo Beds that are predominantly calcareous mollisols and vertisols (Beach et al. 2002; Day 1993:122; King et al. 1992). Underlying the area is a karst belt that runs through central Belize. The Cretaceous to Early Tertiary period limestone substrate is composed primarily of calcium, barium, and strontium (Day 1993). The soils are mostly acidic with a range of 5.5-6.5 on the pH scale and are often less than 50 cm thick. Probes at Actuncan have reached depths of more than 3 m, however, indicating that limestone bedrock was not

readily available as a source for construction material. This is particularly important to this study as: 1) the box terraces of the agricultural plot systems are not placed on bedrock like most terraces, but, rather, a clayey soil matrix; and 2) berms at Actuncan take the form of earthen berms created out of yeso instead of chert and limestone cobbles that are traditionally used to create berms (Kunen 2001:339).

Soils at Actuncan fall under the Yaxa Suite (and the Yalbac Subsuite more specifically), made up of mollisols and vertisols. Vertisols are clay-rich soils (50-70% clay), found in river terraces in the Belize River valley, that form deep cracks during the dry season and become sticky and swell in the wet season (USDA 1999). Grasslands, savannah, open forest, and desert scrub typically grow in vertisols. Irrigation of vertisols is problematic because the soils are slow to drain and become waterlogged easily. They can, however, be brought into use through the channelization and creation of raised fields (Adams et al. 1981; Siemens 1996; Siemens and Puleston 1972). Mollisols have high organic content and are highly productive, and likely contributed to the high capacity for agricultural production throughout the Maya Lowlands (Brady 1990:67). Locally, this type of soil is called “chachakluum” and is considered optimal for maize agriculture (Wyatt 2008:71).

The main soils of the Yaxa Suite are dark colored blocky clays that are neutral or alkaline and well supplied with calcium, magnesium and aluminum, but that have only moderate contents of other nutrients such as iron. In anthropogenic soils in the Northern Settlement Zone, excavations have shown that the soil often exhibited small specks of dark red to black mottling embedded in the dense blocky clay, which may be associated

with magnetite, maghemite, or magnesium (LeCount 2012:15). These clay rich soils are low in potassium and phosphates, essential nutrients for plant growth, but are satisfactory for growing grain crops, including maize (Birchall and Jenkin 1979:35-36). The nearby Melinda suite soils are more nutrient rich due to their location on the Mopan River floodplain, and are ideal locations for agriculture (Cap 2015; Birchall and Jenkin 1979). Within the Yalbac Subsuite, the Piedregal series (on which Actuncan is situated) is one of the most productive soil series in terms of potential productivity using prehispanic

agricultural techniques. A revision by Fedick (2010) of Baillie and colleagues (1992) vague description of the soil capability led to a numbering system that represented the Piedregal series in terms of five main limitations: 1) fertility; 2) erosion; 3) root zone; 4) workability; and 5) drainage. With the number 1 representing the fewest limitations, the Yalbec Subsuite is graded 1 for fertility, 2 for erosion, 2 for root zone, 1 for workability, and 1 for drainage, leading Fedick (2010:57) to categorize the soil as “Capability Class 2,” suggesting a high capability for agricultural production. Despite the general belief that tropical soils are thin and bereft of nutrients, the soils in the Belize River valley, as well as in much of the southern Maya Lowlands in general, are fertile and productive. The limestone substrate and the extensive presence of mollisols make this a prime area for agricultural settlement both in the present day and in the past.