Biochar and anionic polyacrylamide modulated soil hydraulic functions catalyze water saving, root development and yield of basmati rice

Abrol Vikas^1*Peeyush Sharma²Haziq Shabir²S K Gupta¹N K Gupta¹R K Samnotra¹Subash Chandra³Owais Bashir²Sheikh Amjid²Priti Singh¹Abeer Hashem⁴AJAY KUMAR⁵Elsayed Fathi Abd_Allah⁶Manish Kumar^5*Dr. Rubby Sandhu⁷Vinay Chembolu⁸Marcos Lado⁹Dr. Leena Hublikar¹⁰

• ¹Sher-e-Kashmir University of Agricultural Sciences and Technology of Jammu, Jammu, India
• ²Faculty of Agriculture, Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, Srinagar, India
• ³Gandhi Institute of Technology and Management, Visakhapatnam, India
• ⁴King Saud University Department of Botany & Microbiology, Riyadh, Saudi Arabia
• ⁵Amity University Noida, Noida, India
• ⁶King Saud University, Riyadh, Saudi Arabia
• ⁷Lovely Professional University College of Agriculture Science, Phagwara, India
• ⁸Indian Institute of Technology Jammu, Jammu, India
• ⁹Universidade da Coruna, A Coruña, Spain
• ¹⁰KLE Technological University, Hubballi, India

Efficient water use while maintaining rice productivity remains a major challenge amid declining water resources. Biocharwith large surface area and hydrophilic polymers, such as anionic polyacrylamide (PAM), can enhance soil moisture and nutrient retention. However, their combined effects on rice growth and soil hydro-physical properties have not been fully explored. This study evaluated the influence of biochar and PAM on soil properties, water retention, root growth, and rice performance under two establishment methods: the System of Rice Intensification (SRI) and Conventional Method (CM). A two-year field experiment was conducted on sandy clay loam soil using a split-plot design with SRI and CM as main plots and six soil amendment treatments (control, biochar, and polymer) as subplots, replicated thrice.Results showed that SRI produced 15% higher grain yield while using 28.2% less irrigation water compared with CM. SRI also improved soil moisture (SM) content, infiltration rate (IR), hydraulic conductivity (HC), and water productivity (WP) by 6.6%, 5.4%, 9.0%, and 46.5%, respectively. Root length and weight densities under SRI were 1.31 and 1.62 times higher than under CM. The application of biochar (10 t ha⁻¹) and PAM (10 kg ha⁻¹) significantly enhanced soil physical attributes, resulting in 1.22 and 1.27 times increases in grain yield and root length density, respectively, over the control. Integrating biochar and polymer with SRI reduced irrigation water use by 39.45% compared with CM. Overall, the combination of biochar (10 t ha⁻¹) and PAM (10 kg ha⁻¹) under SRI effectively improved soil hydro-physical properties, root development, water productivity, and rice yield in the sub-humid tropical Inceptisols of northern India.