|Olk, Daniel - Dan|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/25/2001
Publication Date: 10/25/2001
Citation: OLK, D.C., JIMENEZ, R.R., MOSCOSO, E. SOIL PHENOLS CYCLING AND ORGANIC N AVAILABILITY DURING AN IRRIGATED RICE CROP. AGRONOMY ABSTRACTS. 2001. CD-ROM. MADISON, WI. ASA-CSSA-SSSA.
Technical Abstract: Long-term intensive lowland rice cropping at initially high yields has been shown to result in an accumulation of lignin-derived phenols in the soil and decreased crop availability of soil nitrogen (N). A causal linkage of accumulating phenols to inhibited soil N availability was investigated here by measuring phenol and N contents in the labile mobile humic acid (MHA) fraction during a four-year field experiment. Phenols were extracted by tetramethylammonium hydroxide and analyzed by gas chromatography. The MHA of the field treatments having the greatest accumulation of phenols (anaerobic decomposition of crop residues, rice-rice rotation, high N fertilizer input) better retained N against release during the growing season than did the MHA of treatments having less phenol accumulation (aerobic decomposition, rice-maize rotation, zero N fertilizer input). Nitrogen release was evaluated through the MHA content both of total N and of N-labeled fertilizer. The association of phenol accumulation with inhibited N release strengthened across years and was stronger in late season than in early season. The association was initially clearest for the smallest phenolic compounds and became apparent in successive years for progressively larger phenolic molecules. It was much weaker in the phenol-depleted calcium humate fraction than in the MHA.