Regional Analysis of Soil Carbon Stocks Under Maize Production: Comparison of Data Sets and Effects of Management Practices.

Many studies have examined effects of specific combinations of soil series and management practices on soil carbon stocks, but data and approaches are needed for scaling up such results to large regions. We analyzed 31,041 records from the Cornell Nutrient Analysis Laboratory (CNAL) and compared them to results from the SSURGO geospatial dataset for a temperate region of 12.6 million hectares (New York State). We compare the results of these two data sets by soil series to improve estimates of soil carbon stocks including effects of management practices. Based on 7,859 samples from grain fields and 23,182 samples from silage fields from CNAL, soil organic matter (SOM) in the top 20 cm was highly variable, with a coefficient of variation of 49% and a range from 0.2 to 5.7%.   The mean SOM of silage fields (3.69±1.0%) was significantly higher (p <0.0001) than that of grain fields (3.16±0.94%), probably due to greater manure application on silage fields. Fields used continuously for maize grain production (>5 years) had significantly lower mean SOM than fields used continuously for silage or alfalfa production.  For each of the 10 soil series with the largest area in maize production, the mean SOM from the CNAL dataset was lower than that from the SSURGO dataset.  The CNAL data also showed more variation in SOM among series than did the SSURGO data. Scaling up by soil series to the entire maize-growing area, total soil carbon to 20 cm depth was 26.51 Tg based on the CNAL data, which is only 72% of the value calculated from the SSURGO data. This research is part of a larger ongoing project; see abstract entitled “An Integrative Approach to Carbon, Nitrogen, and Greenhouse Gas Accounting and Management in Corn Production Systems” by Wolfe et alia.