Carbon sequestration in organic and conventional corn production system

Global warming brought about by increasing concentration of green house gases (GHG) in the atmosphere, particularly that of CO sub 2, is a major concern due to its impact on climate change. The intensity and frequency of typhoons, drought and flooding increased due to the change in climate and these have a negative impact on crop productivity and food security. Alternative farming practices that can potentially reduce CO sub 2 emission and optimize the efficiency of plant and soil carbon sequestration is therefore necessary. Thus, this experiment was conducted to determine and compare the potential contribution of organic and conventional corn production systems on carbon sequestration based on plant biomass and soil organic carbon accumulation. The field experiment was conducted at the Central Experiment Station, Pili Drive, UP Los Baños, College Laguna [Philippines] from June to September 2012 for the wet season experiment, and from February to May 2013 for the dry season experiment. Four fertilizer treatments and two corn cultivars served as mainplot and subplot, respectively, and were laid out in split-plot in RCBD with three replications. The cultivars evaluated were USM Var 10, a high yielding open-pollinated variety and Crystal, a farmer-selected open-pollinated cultivar. Fertilizer treatments were control, inorganic fertilizer (138 kg N from urea), and organic fertilizer in the form of vermicompost. The rate of vermicompost used during the wet season was 8 t/ha while during the dry season 8 and 10 t/ha was used. Data on root and shoot biomass and organic carbon content, soil organic carbon, and bulk density were monitored at 30 and 60 days after sowing during the wet season and until 90 days after sowing during the dry season. Plant carbon (C) sequestration was calculated based on root and shoot biomass and on the carbon content of plant tissues. Soil C sequestration was calculated based on soil organic carbon content, soil depth and bulk density. For both wet and dry season experiments, the use of inorganic fertilizer contributed to highest total plant C sequestration. Between the two cultivars, USM Var, a 10 high yielding open-pollinated variety, contributed more to C sequestration. Soil C sequestration was likewise highest using inorganic fertilizer, but values did not differ during the wet and dry season. The total carbon sequestration using inorganic fertilizer was undeniably much greater than using vermicompost. However, considering the adverse environmental impacts of inorganic fertilizer, (i.e. CO2 emission during its manufacture, transport, and use; deterioration of soil and water quality; and impact on human) this may reduce its C sequestration potential.