CARBON AND NITROGEN MINERALIZATION IN ROW AND INTERROW AREAS OF CHISEL AND RIDGE-TILLAGE SYSTEMS

Understanding linkages between C and N cycles will improve our ability to estimate soil N supplying power. This study investigated temporal patterns in C and N mineralization at two sampling locations within ri dge tillage and chisel plow systems. The study was conducted on a Bran dt silty clay loam (fine-silty over sandy or sandy skeletal, mixed Pac hic Udic Haploboroll) near Aurora, SD. Maize (Zea mays L.) was planted at the site in 1992 and 1993. In the chisel plow treatment, net C min eralization rates in samples from the row and interrow areas were simi lar. However, in the ridge tillage treatment, net C mineralization rat es in samples from row areas were higher than those from valley areas for seven and similar for five, of the 13 sampling dates. In 1992 and 1993, net N mineralization was influenced sampling date but not sampli ng location. Net N and C mineralization peaks did not occur at the sam e time. Mineralization peaks occurred during early spring for N and du ring late spring to mid summer for C. Temporal changes in mineralized C:N ratios indicate that organic substrate quality changed during the year. This study shows that C and N mineralization linkages are comple x and vary in both space and time, and suggest that problems associate d with relating chemical N mineralization indices to field responses m ay result from difficulties associated with estimating the effect of t illage or climatic parameters on microbial activity.