Effects of Organic Amendments on Enzymes Activities in a Calcareous Sandy Soil

Abstract: This study was conducted to assess the impact of some organic amendments on enzyme activities and soil organic carbon (SOC) content of a Calcaric Regosol. The organic amendments included poultry manure compost (CM), sugarcane (Saccharum officinarum) bagasse biomass (SBB), and its biochar (SBBC). Chemical soil properties and some enzyme activities were analyzed after 2, 4, 8, and 12 months (M₂, M₄, M₈, and M₁₂, respectively) of soil incubation. Five treatments including Control soil, SBB, SBBC, CM, and the mixture of SBBC + CM in the ratio of 1 : 1 were considered. There were three levels of organic amendments: L₁: 1.25%, L₂: 2.5%, and L₃: 5%. The results indicated a considerable increase in SOC content and enzyme activities following the addition of organic amendments to the soil. Both the SOC content and enzyme activities were impacted by the type of organic amendments, levels of input, and the duration of incubation (p < 0.001). Compared to the control (untreated soil), the activity of alkaline phosphatase significantly increased from 221.2 (CML₁M₂) to 1094% (SBBL₃M₁₂) and acid phosphatase activity varied from 108.2 (SBBCL₃M₂) to 1063% (SBBL₃M₁₂) in the treated soils. The CML₃M₁₂ treatment had the highest impact on β-glucosidase activity with a rise of 1256.5% in comparison with the control. Similarly, the SBBCL₃M₈ treatment led to the highest Invertase activity. Application of organic amendments would be considered as a guaranteed strategy of restoring and increasing SOC storage in calcareous sandy soils.