Soil Organic Matter Response to Cropping System and Nitrogen Fertilization

Abstract

Management to improve soil C and N storage is necessary to increase soil quality. Continuous corn (Zea mays L.) (CC) and a corn‐soybean [Glycine max (L.) Merr.] rotation (CS) in a chisel plow tillage system with six N fertilizer rates in corn were sampled after 8 yr in Illinois. Soil organic carbon (SOC) and total nitrogen (TN) varied with cropping system at DeKalb, but not at Dixon Springs or Urbana. At DeKalb, SOC in the 0‐to 30‐cm depth was 98.6 and 81.4 Mg C ha−1 following CC and CS, respectively. Similarly, TN to a depth of 30 cm at DeKalb was 7.91 Mg N ha−1 with CC and 6.91 Mg N ha−1 with CS. Particulate organic matter (POM) C (POM‐C) and POM N (POM‐N) were also greater following CC in the 0‐ to 30‐cm depth at DeKalb and in the surface 15 cm at Dixon Springs. At DeKalb, POM‐C in the 0‐ to 30‐cm depth was 6.5 Mg C ha−1 following CC and 5.1 Mg C ha−1 following CS, while POM‐N was 0.41 and 0.34 Mg N ha−1, respectively. At Dixon Springs, where POM‐C was 4.9 Mg C ha−1 and POM‐N was 0.34 Mg N ha−1 in the 0‐ to 15‐cm depth following CS, POM‐C and POM‐N were 10 and 9% greater with CC, respectively. These results indicate that cropping system influences soil C and N more than N fertilization, and that this influence is greater in the labile fraction of soil organic matter (SOM) than in total SOM.