Federal officials are unveiling a voluntary programs and initiatives for farmers, ranchers and foresters meant to build on President Barack Obama’s efforts to combat global warming — and don’t require approval from Congress.  Agriculture Secretary Tom Vilsack is set to announce plans today at Michigan State University, where Obama signed the farm bill into law last year.  The efforts aim to reduce greenhouse gas emissions and boost carbon sequestration through grants, low-interest loans, and technical assistance.  Actions include reducing unnecessary fertilizer use, reforesting areas damaged by wildfire and disease and encouraging urban tree planting.  Vilsack says such steps would “help not only the environment but also … improve the bottom line of producers.”  Previous efforts by Obama to tackle climate change have been met with strong Republican objections.