Salinity management using an anionic polymer in a pecan field with calcareous-sodic soil

Area of Science:

• Agricultural Science
• Soil Science
• Environmental Science

Background:

• Soil salinity and sodicity are critical issues for irrigated agriculture in the Trans-Pecos Basin, exacerbated by Rio Grande River water.
• Reclaiming these salt-affected, fine-textured soils is challenging due to low permeability and high shrink-swell potential.
• Conventional methods like subsoiling are costly and often ineffective on these specific soil types.

Purpose of the Study:

• To evaluate the impact of polyacrylamide (PAM) on soil permeability, calcium mineral dissolution, and salt leaching.
• To assess the effectiveness of PAM in improving soil conditions for irrigated agriculture in the Trans-Pecos Basin.
• To determine if PAM application can reduce amelioration costs by utilizing native soil calcium.

Main Methods:

• Polyacrylamide (PAM) was applied at a concentration of 10 mg L during the first seasonal irrigation over three years.
• Soil permeability, in situ calcium mineral dissolution, and salt leaching were monitored in a pecan field in El Paso County, TX.
• Measurements included soil electrical conductivity (EC), sodium adsorption ratio (SAR), and calcium carbonate (CaCO) concentrations.

Main Results:

• PAM application significantly improved water movement and sodium leaching within the effective root zone.
• A notable decrease in CaCO concentrations was observed in the top 45 cm, indicating calcite solubilization and redistribution.
• Soil EC in the top 60 cm decreased from 4.64 to 2.76 dS m, and SAR in the top 75 cm reduced from 13.1 to 5.7 mmol L.
• Pecan nut yields increased by 34% in PAM-treated fields compared to control plots.

Conclusions:

• PAM application enhances soil permeability, facilitating effective leaching of salts and sodium.
• The polymer aids in the utilization of native soil calcium sources to counteract sodicity.
• PAM treatment offers a cost-effective solution for reclaiming salt-affected lands, leading to improved crop yields.