Liming Materials in Combination with Co-Composted Biochar for Subsoil Acidity Amelioration in Southern Laterites of Kerala

Aims: To assess the capacity of co-composted biochar liming material combinations to alleviate surface, subsoil acidity and aluminium saturation.

Study Design: A field experiment was laid out in randomized block design (RBD) replicated thrice with seven treatments viz., ½ LR as Burnt lime (BL) + ½ as Phosphogypsum (PG) + Co-composted biochar (CCB) (5t ha-1), ½ LR as Dolomite (DL) + ½ as PG + CCB (5t ha-1) and ½ LR as BL + ½ as PG & Magnesium sulphate (MS) (3:2) + CCB (5t ha-1) each @ 100 per cent lime requirement (LR) and @ 75 per cent LR including an absolute control.

Place and Duration of the Study: Instructional Farm, College of Agriculture, Vellayani, Thiruvananthapuram, Kerala, between June 2023 and September 2023.

Methodology: A field experiment was laid out and soil samples from four depths viz., 0-15, 15-30, 30-60 and 60-90 cm were analysed for soil pH, exchangeable acidity and Al saturation at the beginning of the experiment and at crop harvest. Plant biometric observations and yield attributes were also assessed at crop harvest stage.

Results: The application of ½ LR as BL + ½ as PG + CCB (5t ha-1) @ 100 per cent LR exhibited higher values of soil pH (5.74, 5.53, 5.45 and 5.28) up to 90 cm depth, effective alleviation of exchangeable acidity (0.377 meq 100g-1, 0.877 meq 100g-1, 1.057 meq 100g-1), potential acidity (24.0 meq 100g-1 , 30.0 meq 100g-1 , 32.0 meq 100g-1) and pH dependent acidity (23.623 meq 100g-1, 29.123 meq 100g-1, 30.943 meq 100g-1) in the subsoil (15-90 cm) and higher reduction in Al saturation (3.66 %, 8.36 %, 21.5 %, 22.3 %) up to 90cm depth, higher rate of crop growth and yield at the harvest stage.

Conclusion: The combined application of liming materials and co-composted biochar could achieve effective moderation of soil acidity and Al toxicity.