Soil organic carbon changes at the field scale:  Since 1978, long-term tillage and crop management practices have evaluated the impact of conservation and conventional tillage management on soil organic carbon (SOC) contents using row crops (corn, soybeans, cotton).  Annual soil sampling revealed that SOC contents in top soils are almost 2-fold higher under conservation tillage than conventional tillage, and most of the SOC increase occurs near the immediate soil surface.

Resource:
Simulated Soil Organic Carbon Response.. (PDF)

Using biochar as a soil amendment: Biochar application to agricultural soils is an emerging management option to increase soil fertility and improve soil physical and chemical properties. Research results from laboratory experiments provided guidelines for developing designer biochars for use as amendments in sandy soils. These biochars were designed from locally available crop and manure feedstocks and were added to soils to improve soil carbon sequestration, increase water retention, improve fertility, stimulate soil enzymes and microbial communities.

Resource:
Soil health, crop productivity... (PDF)

Ameliorating hard setting subsoil layers with designer biochars: Biochars were specifically designed to improve soil chemical properties and water hydraulics in a SE USA Coastal Plain hard setting subsoil layer. Additions of designer biochar improved soil organic carbon contents, increased plant nutrient levels, and allowed water to infiltrate through a dense subsoil layer. These improvements are important to increase crop production in sandy soils.

Resouces:
Ameliorating soil chemical proerties... (PDF)
Efficacies of designer Biochars.. (PDF)
Biochars impact on water movement... (PDF)

Improve soil quality with hydrochar amendments: Hydrochar is a carbonaceous solid made from heating wet swine manure under pressure. ARS scientists and university collaborators found that swine manure hydrochar improved nutrient retention in the soil matrix. This nutrient retaining capacity of soil manure hydrochar reduced nutrient leaching and improved water quality of soil leachates.

Resource:
Leachate water quality of soils amended... (PDF)