Effects of acidifiers on soil greenhouse gas emissions in calcareous soils in a semi-arid area.

In most agricultural fields, when soil pH is high, elemental sulfur or sulfuric acid are used to reduce soil pH and increase the availability of macro and micronutrients for optimum crop yield. However, how these inputs impact soil greenhouse gas emissions is unknown. This study aimed to measure the amount of greenhouse gas emissions and pH after the application of various doses of elemental sulfur (ES) and sulfuric acid (SA). Using static chambers, this study quantifies soil greenhouse gas emissions (CO, NO, and CH) for 12 months after the application of ES (200, 400, 600, 800, and 1000 kg ha) and SA (20, 40, 60, 80 and 100 kg ha) to a calcareous soil (pH 8.1) in Zanjan, Iran. Also, in order to simulate rainfed and dryland farming which are common practices in this area, this study was conducted with and without sprinkler irrigation. Application of ES slowly decreased soil pH (more than half a unit) over the year whereas application of SA temporarily reduced the pH (less than a half unit) for a few weeks. CO and NO emissions and CH uptake were maximum during summer and lowest in winter. Cumulative CO fluxes ranged from 1859.2 kg CO-C ha year in the control treatment to 2269.6 kg CO-C ha year in the 1000 kg ha ES treatment. Cumulative fluxes for NO-N were 2.5 and 3.7 kg NO-N ha year and cumulative CH uptakes were 0.2 and 2.3 kg CH-C ha year in the same treatments. Irrigation significantly increased CO and NO emissions and, depending on the amount of ES applied, decreased or increased CH uptake. SA application had a negligible effect on GHGs emissions in this experiment and only the highest amount of SA altered GHGs emissions.