Cacao leaf litter decomposition under different moisture and pH: Characteristic of soil N mineralization (NH4+ and NO3-) and Greenhouse gas CO2, CH4, N2O flux emission

Abstract

Plants litter as soil organic matter turn over to soil by the decomposition process. Decomposition is regulated by environmental factors, such as soil water content and pH. High water content (90%) and pH 6.2 increased CO2 gas production rate, lowest water content (30%) and pH 4.9 increased NH4+ N-mineralization into the soil as decomposition result. In this study, we investigated cacao leaf litter decomposition in soil. Cacao leaf litter was applied in a 100 mL polypropylene bottle with 70 g air-dried soil, but only the soil was applied as a control. For the litter-amended treatments, 2 g (oven-dry weight) with 2 mm sized cacao leaf litter was placed on the soil surface. The treatment with different soil moisture and pH regimes were soil moisture and pH of 30% and 4.9 (SLWC30i), 30% and 6.2 (SLWC306), 60% and 4.9 (SLWC60i), 60% and 6.2 (SLWC606), 90% and 4.9 (SLWC90i), 90% and 6.2 (SLWC906), respectively. All treatment was incubated at 25C under the dark condition for 28 days. Extractable NO3- and NH4+ concentration, and soil greenhouse gas (CO2, CH4, N2O) were measured. Highest extractable NO3- and NH4+ concentration showed in SWC906 (30.7 mg N kg-1) and SLWC606 (87.1 mg N kg-1), respectively. Soil greenhouse gas production rate highest in water content 90% pH 6.2, CO2 was 3.82 kg C period-1, CH4 was 0.0089 kg C period-1, N2O was 0.016 kg N period-1.