Soil erosion and rainfall-induced runoff are well studied although under field conditions remain somewhat enigmatic. This study quantifies the relationship between rain, overland flow (runoff), erosion and size characteristics of the sediment in China’s northern “corn-belt” during the 2016 growing season. The study site was at the Heilongjiang Experimental Farm (47º23′N, 126º51′E), which is located near Guangrong village in China’s core Mollisol region. Two tillage treatments were evaluated: no-till and conventional till. Each treatment was replicated on runoff plots having 5° (9%) and 7° (12%) slopes. The 5° plots were established in 2006. The 7° plots were established in 2009. Plot size is 20 m long and 4.5 m wide. The experimental control plot is bare soil plot on 5° slope. Results are 394.3 mm rain fell during 54 events between May and November 2016. Runoff as overland flow occurred 14 times in the control, accounted for 25.9% of the precipitation and caused 54.5 tons/ha erosion. At the other end of the data, runoff only occurred twice in the 5° no-till plot and caused only 0.2 tons/ha erosion. Detailed analysis of three rain fall events further validated significant differences in runoff and erosion with each treatment as well as significant differences in size distribution of transported soil solids. Soil solid size distribution and amounts were valuable for describing and analyzing runoff and soil loss processes under different treatments.

Mollisols a.k.a., Black Soils or Prairie Soils make up about 916 million ha, which is 7% of the world’s ice-free land surface. Their distribution strongly correlates with native prairie ecosystems, but is not limited to them. They are most prevalent in the mid-latitudes of North America, Eurasia, and South America. In North America, they cover 200 million ha of the United States, more than 40 million ha of Canada and 50 million ha of Mexico. Across Eurasia they cover around 450 million ha, extending from the western 148 million ha in southern Russia and 34 million ha in Ukraine to the eastern 35 million ha in northeast China. They are common to South America’s Argentina and Uruguay, covering about 89 million and 13 million ha, respectively. Mollisols are often recognized as inherently productive and fertile soils. They are extensively and intensively farmed, and increasingly dedicated to cereals production, which needs significant inputs of fertilizers and tillage. Mollisols are also important soils in pasture, range and forage systems. Thus, it is not surprising that these soils are prone to soil erosion, dehumification (loss of stable aggregates and organic matter) and are suffering from anthropogenic soil acidity. Therefore, soil scientists from all of the world’s Mollisols regions are concerned about the sustainability of some of current trends in land use and agricultural practices. These same scientists recommend increasing the acreage under minimum or restricted tillage, returning plant residues and adding organic amendments such as animal manure to maintain or increase soil organic matter content, and more systematic use of chemical amendments such as agricultural limestone to replenish soil calcium reserves.