Effect of Silt-Fortified Organic Manures on Soil Chemical and Biological Properties under Cassava (Manihot esculenta Crantz) Cultivation in Kuttanad Soils of Kerala

The promotion of safe and sustainable organic farming necessitates production and availability of quality organic inputs in adequate quantities. A field experiment was conducted in Kuttanad, Kerala during 2023-2024 in RCBD with seven treatments and replicated thrice to evaluate the effect of silt and silt fortified organic manures on soil chemical properties and enzymatic activities at different growth stages of cassava. The treatments included fortified poultry manure, fortified crop-residue composts (paddy straw, banana pseudostem, and water hyacinth), fortified farmyard manure, silt alone, and farmyard manure alone (control). At harvest, fortified poultry manure recorded the highest available nitrogen (265.33 kg ha⁻¹), phosphorus (52.90 kg ha⁻¹), and potassium (345.22 kg ha⁻¹), indicating superior enhancement of soil fertility. Fortified organic amendments significantly improved soil pH, organic carbon, and available N, P, and K compared to control and silt alone. Crop-residue composts also improved soil carbon status and potassium availability, whereas silt applied alone was comparatively less effective. Overall, the results demonstrate that silt-fortified organic manures, particularly poultry manure and crop-residue composts, are effective for improving soil chemical fertility and biological functioning as evidenced by increased dehydrogenase, urease, and phosphatase activities in cassava-based systems of Kuttanad.