Carbon Sequestration in No-till Soils Managed Under Different Levels of Sprinkler Irrigation in the Central Great Plains.

Enhancing carbon (C) sequestration in agricultural soils is becoming increasingly important for reducing net emissions of greenhouse gases and improving soil productivity. In arid and semi-arid regions, supplemental irrigation is considered as one of the potential management practices to enhance soil C sequestration. No-till and diverse cropping systems under irrigation can be particularly beneficial for soil C sequestration because of high biomass input and reduced soil disturbance. Irrigation can influence soil C balance by two contrasting mechanisms. It can enhance C storage by increasing biomass production, but it can also accelerate soil organic matter decomposition and thus reduce C storage by increasing soil water content and biological activity. In the Great Plains region, particularly in the High Plains of Kansas, concerns over water level declines in the Ogallala Aquifer are prompting the adoption of limited or deficit irrigation strategies to reduce groundwater withdrawal. The reduction in irrigation amounts may concomitantly influence rates of soil C sequestration. Experimental data on: 1) the magnitude of soil C sequestration in irrigated lands and 2) impacts of reduced levels of irrigation on C sequestration are very few. Thus, this study assesses the impacts of different levels of sprinkler irrigation on soil-profile organic C and inorganic C distribution in two no-till systems located at Garden City and Tribune, KS. Corn (Zea mays L.), winter wheat (Triticum aestivum L.), grain sorghum (Sorghum bicolor L.), and sunflower (Helianthus annuus L.) managed under no-till with six levels of sprinkler irrigation at Garden City and three levels at Tribune were studied. Soil samples, collected to 1 m depth, will be analyzed for organic and inorganic C in bulk soil, macroaggregates, and microaggregates. Results will be presented and discussed at the meetings.