Abstract
Soil moisture is the main limiting factor for crop growth and the sustainable development of oases in arid desert areas. Therefore, the temporal and spatial variation and infiltration laws of oasis soil moisture should be studied. The objective of this study is to reveal the influencing factors of the spatial–temporal variation of layered soil and sediment moisture and infiltration characteristics under irrigation in desert oases. Hydraulic conductivities were measured using the double-ring infiltrometer, while the regional and site soil moistures were measured and calibrated using weighted method and neutron moisture meter. Deterministic spatial interpolation methods, including multiquadric radial basis function, inverse distance weighted, and local polynomial regression isogram, were adopted to map the regional distribution of hydraulic conductivities, spatial soil moistures, and spatial–temporal isogram of the point site soil moistures in Yaoba Oasis, respectively. Results showed that the leading influencing factors of the (1) regional spatial soil moisture were soil and sediment permeability, stream link direction, microclimate, and dewfalls; (2) spatial layered soil and sediment moistures were microclimate and dew condensation; and (3) spatial–temporal variation at the point site profiles were soil texture, water requirement, and preferential flow. Under irrigation, soil moisture increased significantly, in which the maximum increase was 10.8 times the original state, while the recharging depth substantially increased up to 580 cm with the preferential flow. The spatial–temporal variation of the soil moisture under irrigation indicated that the best irrigation frequency should be 15 days per time. Moreover, the infiltration process can be divided into the preferential flow, piston flow, and balanced infiltration stages.
Highlights
Oasis is the most frequent and active region of human activities in arid areas in the world [1], such as the Middle East, Mexico, most parts of Africa, parts of northwestern America, and pockets of India, Central Asia, and northwestern China [2]
Numerous investigations have been conducted on oasis soil moisture in terms of the following three aspects: (1) the relationships between soil moisture and groundwater dynamics [10,11,12,13], soil salinization [14,15,16], vegetation, and land use pattern [17,18,19]; (2) the spatial–temporal variation and temporal stability of soil moisture in oases [20,21,22,23,24,25]; and (3) the study of soil water infiltration characteristics and migration laws [26]
According to the spatial distribution map of soil moisture measured before the first irrigation in each layer (Figure 4), the soil moisture at depth of 0–100 cm is large in the north and east parts and small in the south and west
Summary
Oasis is the most frequent and active region of human activities in arid areas in the world [1], such as the Middle East, Mexico, most parts of Africa, parts of northwestern America, and pockets of India, Central Asia, and northwestern China [2]. Studying the temporal and spatial variation characteristics of soil moisture is of considerable importance to understand the agricultural irrigation regime and provide further scientific basis for the development of oasis agriculture [8,9]. Numerous investigations have been conducted on oasis soil moisture in terms of the following three aspects: (1) the relationships between soil moisture and groundwater dynamics [10,11,12,13], soil salinization [14,15,16], vegetation, and land use pattern [17,18,19]; (2) the spatial–temporal variation and temporal stability of soil moisture in oases [20,21,22,23,24,25]; and (3) the study of soil water infiltration characteristics and migration laws [26]
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