Spatiotemporal Soil Carbon Dynamics in Corn Silage Production Systems Receiving Liquid Dairy Manure.

Maximizing C storage in agricultural soils requires a better understanding of how agronomic management and terrain interact to influence soil carbon dynamics.  The objective of this on-farm, field-scale study was to quantify the spatial and temporal changes in soil organic (SOC) in corn silage production systems in relation to management factors (irrigation, manure application method, cover cropping) and terrain (landscape position, soil texture).  The study was conducted on adjacent 65-ha fields in west central Minnesota from 2006 to 2015.  Each field began receiving irrigation in May 2009 and manure management included fall injected liquid dairy manure (West field) and spring fertigation with liquid dairy manure (East field).   Results show that SOC to 15 cm depth varied among some years, but showed no net change from 2006 to 2015 in either field.  However, SOC was highly spatially dynamic in both fields, and was consistently lowest at the highest (top slope) landscape position.  Differences in SOC between landscape positions were consistent through time.   Preliminary results suggest that current management practices and rates of C removal in corn silage do not detrimentally impact SOC levels across varied landscape positions in west central Minnesota calcareous soils.