Salinity Under Pressure:​​ Evaluating Gypsum and Biochar as Remediation Agents in Saline Soils

Grade:

7

Teacher:

Karen Maninang

Soil salinity is a critical agricultural challenge in arid regions such as Yuma, Arizona, where limited rainfall and continuous irrigation cause dissolved salts to accumulate in the root zone. Elevated salinity reduces soil water potential, creates osmotic stress, disrupts nutrient balance, and significantly decreases crop productivity. While gypsum and biochar are commonly recommended as soil amendments for saline soils, their short-term effectiveness in reducing measurable salinity remains unclear. This study investigated whether adding gypsum and biochar to salt-treated soil could reduce soil salinity as measured by electrical conductivity (EC). A controlled experimental design was implemented using three treatment groups: Set-Up A (Control – fresh water), Set-Up B (Salt-only), and Set-Up C (Salt + Gypsum + Biochar). Soil samples underwent a standardized soil–water extraction procedure, and EC was measured using a Neulog conductivity sensor to quantify dissolved ion concentration. Multiple trials were conducted to ensure reliability and reproducibility of results. Results demonstrated that salt irrigation significantly increased EC values in Set-Up B, confirming successful induction of salinity stress. Set-Up C showed similarly high EC values but different stabilization patterns, suggesting that gypsum and biochar altered ion interactions rather than immediately reducing total dissolved salts. Because electrical conductivity measures overall ion concentration and does not distinguish between harmful sodium (Na⁺) and beneficial calcium (Ca²⁺), the findings indicate that soil amendments may improve soil chemistry and root-zone conditions without producing an immediate decrease in EC. Although the original hypothesis predicted an immediate reduction in salinity, the data revealed the complexity of soil chemical dynamics under saline conditions. This project provides meaningful scientific insight into short-term versus long-term remediation strategies and emphasizes the importance of extended monitoring when evaluating sustainable soil management solutions in desert agriculture.

Project presentation

Research paper