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Title: TILLAGE INTENSITY AND FERTILITY LEVEL EFFECTS ON NITROGEN AND CARBON CYCLING IN A VERTISOL

Author
item Torbert, Henry - Allen
item Potter, Kenneth
item Morrison Jr, John

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Because of the high erosion potential, efforts have been undertaken to develop conservation tillage systems for the high clay soils found in Texas. These soils are very difficult to manage for production because of their physical characteristics, which include shrinking and swelling, being very sticky when wet, and having a limited range of soil water contents when soil tillage can be performed. This study focused on examining the effects of tillage intensity and fertility level on soil organic matter and nitrogen content. The results indicated that the long term effect of increasing the tillage intensity could be to reduce the organic matter in these soil.

Technical Abstract: Because of erosion problems associated with vertisols, an effort has been undertaken to evaluate the effect of tillage intensity and to develop a conservation tillage systems on these soils. The objective of this study was to examine the impact of tillage intensity and fertility level on C and N cycling in a vertisol. Soil samples (0- 10, 10-20, and 20-30 cm depth increments) were collected from a Houston Black soil (fine, montmorillonitic, thermic Udic Pellusterts) with five different levels of tillage intensity, varying from no tillage to complete residue burial. The experiment was a split plot design with 5 replications. The main plots were 5 levels of tillage intensity (chisel tillage, reduced tillage, row tillage, strip tillage, and no tillage) and the subplots were soil fertility level with either high or low fertilizer rate. Total N, total P, organic C, inorganic N, and C:N ratio were measured on soil samples as well as the potential C mineralization, N mineralization, C turnover and C:N mineralization ratio during a 30 d incubation. The high fertilizer rate increased total P and organic C. Potential soil N mineralization was decreased at the 0-10 cm depth and increased at the 20-30 cm depth by the high soil fertility treatment. Chisel tillage decreased total N and P in the 0-10 cm depth, but increase total N and P at the 10-20 cm depth. Tillage intensity increased C mineralization and C turnover, but reduced N mineralization at the 0- 10 cm depth. The results indicate that intensively tilled soil had a greater capacity for C mineralization and for reductions in soil organic C levels compared to less intensively tilled systems.