Carbon dioxide enrichment and nitrogen fertilization effects on cotton (Gossypium hirsutum L.) plant residue chemistry and decomposition

• Published in: Plant and soil 2000-01, Vol.220 (1/2), p.89-98
• Main Authors: Booker, Fitzgerald L., Shafer, Steven R., Wei, Cai-Miao, Horton, Stephanie J.
• Format: Article
• Language: English
• Subjects: Acid soils; Agricultural site preparation; Agronomy. Soil science and plant productions; Atmospherics; Biological and medical sciences; Carbohydrates; Carbon; Carbon dioxide; Chemical, physicochemical, biochemical and biological properties; Cotton; Decomposition; Fertility; Fertilization; Fundamental and applied biological sciences. Psychology; Gossypium hirsutum; Leaves; lignin; Nitrogen; Organic matter; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Plant biomass; Plant roots; Plants; proanthocyanidins; Residues; Respiration; Sand soils; Sandy soils; Soil fertility; Soil respiration; Soil science; Soils; Tillage; total non-structural carbohydrates
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1023/a:1004773404948

Increased atmospheric carbon dioxide (CO₂) concentration will likely cause changes in plant productivity and composition that might affect soil decomposition processes. The objective of this study was to test to what extent elevated CO₂ and N fertility-induced changes in residue quality controlled decomposition rates. Cotton (Gossypium hirsutum L.) was grown in 8-1 pots and exposed to two concentrations of CO₂ (390 or 722 μmol mol⁻¹) and two levels of N fertilization (1.0 or 0.25 g 1⁻¹ soil) within greenhouse chambers for 8 wks. Plants were then chemically defoliated and air-dried. Leaf, stem and root residues were assayed for total non-structural carbohydrates (TNC), lignin (LTGA), proanthocyanidins (PA), C and N. Respiration rates of an unsterilized sandy soil (Lakeland Sand) mixed with residues from the various treatments were determined using a soda lime trap to measure CO₂ release. At harvest, TNC and PA concentrations were 17 to 45% higher in residues previously treated with elevated CO₂ compared with controls. Leaf and stem residue LTGA concentrations were not significantly affected by either the elevated CO₂ or N fertilization treatments, although root residue LTGA concentration was 30% greater in plants treated with elevated CO₂. The concentration of TNC in leaf residues from the low N fertilization treatment was 2.3 times greater than that in the high N fertilization treatment, although TNC concentration in root and stem residues was suppressed 13 to 23% by the low soil N treatment. PA and LTGA concentrations in leaf, root and stem residues were affected by less than 10% by the low N fertilization treatment. N concentration was 14 to 44% lower in residues obtained from the elevated CO₂ and low N fertilization treatments. In the soil microbial respiration assay, cumulative CO₂ release was 10 to 14% lower in soils amended with residues from the elevated CO₂ and low N fertility treatments, although treatment differences diminished as the experiment progressed. Treatment effects on residue N concentration and C:N ratios appeared to be the most important factors affecting soil microbial respiration. The results of our study strongly suggest that, although elevated CO₂ and N fertility may have significant impact on post-harvest plant residue quality of cotton, neither factor is likely to substantially affect decomposition. Thus, C cycling might not be affected in this way, but via simple increases in plant biomass production.