Hydrophysical properties of the soil to implement irrigation systems in the semi-arid region (Centro Rivera - Bolivian Central higland)

Roxana Copa Bobarin; Roberto Miranda Casas

Abstract

The semi-arid climate zones have low water availability, quantified based on the average annual precipitation, in relation to evapotranspiration. Soils accumulate soluble salts whose distribution, composition and concentration depend on the characteristics and water flow in the profile. The present work evaluates the physical, chemical and hydraulic properties of the soil in four sampling points of the community Centro Rivera, in plots with alfalfa under irrigation. The cultivation of alfalfa (Medicago sativa) is irrigated with waters of the Desaguadero River, these waters are characterized as highly saline waters, mainly in the dry season. Soil properties, both physical and hydro-chemical, are affected by the quality of the irrigation water and the climate. The high sediment content of the water (555 mg.l^-1) favors the formation of surface horizons with a higher content of fine particles, silt and clay, contributing with more than 700 kg ha^-1 of sediments per year, resulting in a lower apparent density, Low rates of infiltration velocity and difficulty in water movement, resulting in slow to moderately slow permeability across the soil profile. Soils are saline due to high evapotranspiration rates (> 1500mm year^-1) and low rainfall (<400mm year^-1) in this region. Also, water retention of the soil is affected by salinity.