Greenhouse Gas Emissions Affected By Tillage, Surface Mulch and Fertilization Managements For Organic Vegetable Productions.

Management practices for agricultural production can have a significant impact on greenhouse gas emissions from soils. The aim of this study was to investigate the effects of tillage systems and surface mulch practices on fluxes of N2O and CO2 from the vegetable field transitioning to organic farming. The experiment was conducted on an Annapolis fine sandy loam at CMREC (Central Maryland Research and Education Center) Upper Marlboro Facility, Upper Marlboro, Maryland. The four treatments used in the study were: conventional tillage with bare ground (BG), conventional tillage with black plastic mulch (BP), strip-tillage (ST), and no-tillage (NT). Winter cover crops (rye, crimson clover and forage radish) were planted late August in all the plots and flail-mowed late April prior to applying the treatments. Beside nitrogen provide by cover crops, mixed fertilizers (chicken manure and feather meal) were hand spread along the plant rows at preplanting at 84 N kg/ha in the BP plots and at preplanting and sidedressing in the plots of BG, NT and ST at rates of 45 and 39 N kg/ha, respectively. Eggplant seedlings were machine transplanted in late May at a population density of 24,000 plants/ha. Surface drip irrigation was used during eggplant growing season when water supply from rainfall was not sufficient. Greenhouse gas samples were taken from two locations in each plot: the plant row and the inter row. Gas samples were usually collected right after major field operations, rainfall and irrigation events. Greater CO2 emissions were found after mowing cover crops and when soil moisture was higher in NT and ST treatments during early growing season. Greater N2O emission was found from the BP treatment from early to middle growing season and from the BG treatment in early and later growing seasons, especially after heavy rainfall. The overall N2O emission during eggplant growing season was the greatest from the BP plots, followed by BG and the lowest in the NT plots. Our findings suggest that the use of NT and ST in the organic vegetable production may reduce N2O emissions, compared to conventional tillage. Though the use of black plastic mulch could promote crop early mature and thus provide greater profit for early marketing, it created a warmer and moister microenvironment that led to greater N2O emission, compared to the BG treatment.