Do Precision Chemical Amendment Applications Impact Sodium Movement in Dryland Semiarid Saline Sodic Soils?

Tulsi P Kharel,Doug Malo,Sharon Clay,Cheryl Reese,Thomas Desutter,David E Clay

doi:10.2134/agronj2017.07.0416

Tulsi P Kharel, Doug Malo + Show 4 more

Open Access

https://doi.org/10.2134/agronj2017.07.0416

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Abstract

Core Ideas Worldwide, salinity and sodicity problems in the dryland systems are increasing.Standard restoration methods created for irrigated systems may not be appropriate in dryland systems.Bypass water flow that occurs in northern Great Plains saline/sodic soils may impact restoration success.New approach EC/SAR ratio to assess saline and sodic soil behavior. Expanding sodicity and salinity problems have placed many northern Great Plains (NGP) soils at the sustainability tipping point. This study assessed the impact of chemical restoration on water and salt transport in undisturbed soil columns collected from three hillslope model landscape positions. The backslope (Redfield), footslope (White Lake), and toeslope (Pierpont) soils had moderate (3.27 ± 0.59), high (7.3 ± 3.34), and very high (13.29 ± 3.2) sodium adsorption ratio (SARe) values, respectively. The soils were treated with KBr and one of four soil amendments (none, H2SO4, CaSO4, and CaCl2). The rapid movement of Br− through the columns suggested that bypass water flow occurred. In addition, a comparison with widely used salinity models (final EC = 0.8 × initial EC/pore volume [PV]) underestimated the leaching requirements by 69, 79, and 41% in the backslope, footslope, and toeslope soils. In the footslope soils with high SAR values, H2SO4 was more effective at promoting Na+ leaching than gypsum or CaCl2. However, in back slope and toeslope soils with moderate and very high SAR values, the chemical amendments were not, and were equally effective at facilitating Na+ leaching, respectively. These findings suggest that chemical amendments should target treatments to problem areas, and that bypass flow can influence their effectiveness. The LOESS regression model suggested that the electrical conductivity (ECe)/SARe ratio was useful for assessing Na+ risks, and that to maintain a water flow rate of 1 mm h−1 in a soil with a SARe value of 1, an ECe value of ≥2 was required.

Highlights

E (ESP), electrical conductivity (EC), and pH
A major problem associated with sodium is clay dispersion, which progressively becomes more severe with decreases in the electrical conductivity determined using saturated paste extract (ECe) > 4 dS m–1 are classified as saline and
Because this research was often conducted using disturbed soil, it is difficult to extend these findings to the structured soils found in northern Great Plains (NGP)

Summary

Introduction

E (ESP), electrical conductivity (EC), and pH. Soil EC and SAR have been historically determined using a saturated paste extract methodology, which are reported as ECe and SARe, respectively. Water infiltration was increased from 0.6 mm h–1 to over 10 mm h–1, and wheat (Triticum aestivum L.) biomass yields were increased from 4060 to 7710 kg ha–1 for sodic soils, when gypsum was applied and subsequently irrigated (Rasouli et al, 2013). In this example, it was likely that the combined impact of Ca2+ and EC helped maintain the soil structure (Sanders, 1988; He et al, 2013). If the EC of the percolating water is low, drainage of soluble salts can contribute to soil swelling and the formation of an impermeable soil layer (Pons et al, 2000; He et al, 2015)

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