Soil Available Water as Influenced by Landscape Position and Aspect¹

Abstract

In dryland farming, stored soil water is an essential source of water for crop production. The amount of water available for storage and crop use in a particular soil in hillslope topography is affected by its position on the landscape. The effect of slope aspect and position on soil water and its changes throughout the year in dryland farming were studied in southeast Nebraska. North, south, and east‐facing slopes of Wymore silty clay loam (Aquic Argiudolls fine, montmorillonitic mesic) were selected for study. Four positions on each slope including summit, shoulder, backslope, and footslope were identified. Water content of the soil from 0 to 150 cm depth in 30 cm increments was measured weekly by neutron scattering for 2 years. Daily precipitation was recorded. Twenty percent more water was available in soils on the north‐facing slope than in soils on the south‐facing slope at planting and throughout the year. Soils on the east‐facing slope were the driest. They contained 50% less available water than did those on the north‐facing slope. Within slope positions, soils on the footslopes and backslopes contained an average of 4 cm more available water than soils on the summits and shoulders. Soil water sampling at planting time for crop management and yield prediction models should be done according to slope position.

Erosion control blankets, organic amendments and site variability influenced the initial plant community at a limestone quarry in the Canadian Rocky Mountains

“…These responses were also seen in similar harsh sites. For example, soils on north facing slopes on dryland in southeastern Nebraska had 20 % more water throughout the year than south facing slopes (Hanna et al, 1982). In a sandy grassland in Hungary, influence of carbon on nitrogen immobilization was more pronounced at sites where organic matter and water were lowest (Török et al, 2000).…”

Spatial Relation of Apparent Soil Electrical Conductivity with Crop Yields and Soil Properties at Different Topographic Positions in a Small Agricultural Watershed

“…They also observed that higher elevation soil sampling locations had lower ECa values compared to lower elevations due to higher volumetric water content at lower elevation positions. Hanna et al [50] observed soil moisture content during crop growth period using neutron probes and reported that within slope positions, soils on the foot slopes and backslopes contained on an average of 4 cm more …”

Efficiency of fall-banded urea for spring wheat production in Manitoba: Influence of application date, landscape position and fertilizer additives

“…Landscape position is another factor that will influence the efficiency of fall-applied N, through the accumulation of water in lower lying areas of the field (Hanna et al 1982). The effects of landscape position are most significant during the early spring period, when ponding of snowmelt runoff often occurs.…”