Brackish water has been widely used to irrigate crops to compensate for insufficient freshwater water supply for agricultural use. The goal of this research was to determine an efficient brackish water use method to increase irrigation efficiency and reduce N₂O emission. To this end, we conducted a field experiment with four salinity levels of irrigation water (1.1, 2.0, 3.5, and 5.0 g·L⁻¹ with drip irrigation) at Hetao Irrigation District (Inner Mongolia, China) in 2017 and 2018. The results show that irrigation with 3.5–5.0 g·L⁻¹ water salinity increased the soil salinity compared with irrigation using 1.1–2.0 g·L⁻¹ water salinity. The soil water content with 5.0 g·L⁻¹ brackish water irrigation was significantly higher than with 1.1–3.5 g·L⁻¹ water salinity due to the effect of salinity on crop water uptake. The overall soil pH increased with the increase in irrigation water salinity. Saturated soil hydraulic conductivity decreased with the increase in irrigation water salinity. These results indicate that brackish water irrigation aggravates the degree of soil salinization and alkalization. The soil N₂O cumulative flux resulting from irrigation with 5.0 g·L⁻¹ water salinity was 51.18–82.86% higher than that resulting from 1.1–3.5 g L⁻¹ water salinity in 2017, and was 32.38–44.79% higher than that resulting from 1.1–2.0 g·L⁻¹ in 2018. Irrigation with brackish water reduced maize yield, and the reduction in yield in 2018 was greater than that in 2017, but irrigation with 2.0 g·L⁻¹ brackish water did not significantly reduce maize yield in 2017. These results suggest that reducing the salinity of irrigation water may effectively reduce soil N₂O emission, alleviate the degree of soil salinization, and increase crop yield.

Efficient and sustainable reclamation of sodic soils is important to agricultural production. With the help of a peristaltic pump, laboratory-leaching experiments for sodic calcareous soils with exchangeable sodium percentage (ESP) of 1, 12.5, and 19 were conducted under atmospheric CO₂ partial pressure to investigate native CaCO₃ mineral dissolution and its contribution to the rehabilitation of moderate sodium-affected soils at the water flow velocities of 2 and 18 mm h⁻¹, respectively. The electrical conductivity (EC), pH, and the Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl⁻, and HCO₃ ⁻ concentrations in the leachates were measured. The exchangeable Na⁺ contents in the soils after leaching were measured and their ESPs were calculated. Results indicated that both soil sodicity and water flow velocity significantly affected native CaCO₃ dissolution and sodic soil reclamation. Almost all of the Ca²⁺ to substitute the adsorbed Na⁺ came from the native CaCO₃ dissolution. The CaCO₃ dissolution rate decreased logarithmically with leachate volume and increased with the initial ESP level. The leachate EC increased with the initial soil ESP level and decreased with flow velocity. The total detected cation concentrations in the leachates within the first six pore volumes (PV) were greater than 3.0–4.6 mmol_c L⁻¹.Low flow velocity was favorable to the improvement of the reclamation rate and reclamation efficiency of sodic soils. After the leaching of six PV, 24.1–36.0% of the Na⁺ adsorbed in the soils with initial ESPs of 12.5 and 19 were removed. Without the aid of extraneous chemical amendments, the gradual reclamation of moderate sodic calcareous soils under suitable management is possible.

Erosion of freeze-thaw soil by meltwater from snow/glacier is one of the main erosion types in high altitude or latitude regions. This study aims to experimentally measure soil erosion processes over partially-unfrozen soil slopes in laboratory. The experiments including three slope gradients of 10°, 15°, and 20°, three water flow rates of 1, 2, and 4 L/min (0.06, 0.12, and 0.24 m³/h), and three thawed-soil depths of 1, 2, and 5 cm were conducted to measure sediment concentration and calculate its delivery rate under seven slope lengths of 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, and 6.0 m. The sediment delivery rates from nonfrozen soil slopes under the corresponding slope gradients, flow rates, and slope lengths also were measured as control treatments. Results showed that the sediment delivery rate from both partially-unfrozen and nonfrozen soil slopes increased logarithmically with slope length. The sediment delivery rate from partially-unfrozen soil slope increased with the increased slope gradient and meltwater flow rate significantly, and the effect of water flow rate on it was greater than that of slope gradient. The thawed-soil depth did not significantly affect sediment delivery rate. The sediment delivery rate from a partially-unfrozen loamy soil slope averagely was 11.4% smaller than that from nonfrozen soil slope. This study is helpful to understand the erosion process of thawing-soil by meltwater from snow/glacier.

Measurement errors on sediment concentration from traditional runoff collection tanks and its correction possibility

Fresh water resource scarcity and soil salt accumulation in the root-zone are two key limiting factors for sustainable agricultural development in the oasis region of arid inland basin, northwest China. The aim of this study was to explore an appropriate irrigation scheme to maintain sustainable crop cultivation in this region. The effects of four irrigation levels (full irrigation, mild deficit, moderate deficit, and severe deficit) and three irrigation methods (border, surface drip and subsurface drip) on soil water and salt dynamics, highland barley (Hordeum vulgare L.) yield, and crop water use efficiency were studied by field plot experiments. The results showed that soil salt in 0-100 cm profile was accumulated under all experimental treatments after one season of highland barley planting, but the accumulated salt mass decreased with the decrease of the lower limit of irrigation. Salt mass in 0-100 cm soil profile under subsurface drip irrigation was 16.8%-57.8% and 2.9%-58.4% less than that under border and surface drip irrigation, respectively. The grain yield of highland barley decreased first and then increased with the decrease of the lower limit of irrigation under surface drip and subsurface drip irrigation, but it was on the contrary under border irrigation. Mean grain yield for all irrigation levels under subsurface drip irrigation was 5.7% and 18.8% higher than that under border and surface drip irrigation, respectively. Water use efficiency increased with the decrease of the lower limit of irrigation, and the averaged water use efficiency of all irrigation levels under subsurface drip irrigation was 11.9% and 14.2% higher than that under border and surface drip irrigation, respectively. Considering economic benefit and irrigation water requirement, subsurface drip irrigation with the lower limit of irrigation of 50%-55% field capacity is suggested for highland barley planting in the arid oasis region. Keywords: arid oasis, highland barley, irrigation method, irrigation level, soil salt balance, water use efficiency DOI: 10.25165/j.ijabe.20231606.7788 Citation: Tang L P, Shi X S, Song Z P, Zhao H, Li F H. Effects of irrigation level and method on soil salt balance and crop water use efficiency in arid oasis regions. Int J Agric & Biol Eng, 2023; 16(6): 158–166.