SOIL CARBON AND NITROGEN POOLS AND AGGREGATION IN RESPONSE TO TYPE AND FREQUENCY OF TILLAGE

Authors: Franzluebbers, Alan; Schomberg, Harry

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/12/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Conservation tillage can improve soil chemical, physical, and biological properties of previously cultivated soils. However, little information exists on the biogeochemical effects of combining no-tillage planting with paraplowing (to improve deep water penetration) or with secondary tillage (to control weeds). We determined soil quality of a kaolinitic Ultisol located in the Southern Appalachian Piedmont of Georgia subjected to no-tillage planting combined with periodic in-row chisel at planting, autumn paraplow, and secondary tillage during the summer. When soil disturbance occurred every year, soil quality deteriorated mostly at 0 to 2.5 cm depth in comparison with less frequent tillage. For most soil carbon and nitrogen pools, in-row chisel maintained higher levels than did paraplow and shallow cultivation. The greater organic matter pools and aggregation near the soil surface with infrequent tillage may have been important in improving crop yield, in part due to biophysical improvement of surface soil structure that presumably led to greater water infiltration and improved water use efficiency.

Technical Abstract: Little information exists on the biogeochemical effects of combining no-tillage planting with paraplowing (to improve deep water penetration) or with secondary tillage (to control weeds). We determined soil carbon and nitrogen pools, (total, particulate, microbial biomass, and mineralizable) and water-stable aggregation at depths of 0 to 25, 25 to 75, and 75 to 150 mm and surface residue carbon and nitrogen from a kaolinitic Ultisol in Georgia. Soil tillage treatments were a factorial arrangement of tillage type [(i) minimal disturbance with in-row chisel at planting, (ii) no-tillage planting with autumn paraplow, and (iii) no-tillage planting with secondary tillage during the summer] and tillage frequency [(i) every year, (ii) every second year, and (iii) every fourth year]. No-tillage planting without further disturbance occurred in remaining years. When soil disturbance occurred every year with paraplow and secondary tillage, soil quality deteriorated mostly at 0 to 25 mm depth in comparison with less frequent tillage. For most soil carbon and nitrogen pools, in-row chisel maintained higher levels than did paraplow and shallow cultivation.