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United States Department of Agriculture

Agricultural Research Service

Title: Tillage, cropping systems,and nitrogen fertilizer source effects on soil carbon sequestration and fractions

Authors
item Sainju, Upendra
item Senwo, Zachary - ALABAMA A&M
item Nyakatawa, Ermson - ALABAMA A&M
item Tazisong, Irenus - ALABAMA A&M
item Reddy, Chandra - ALABAMA A&M

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 13, 2007
Publication Date: May 1, 2008
Repository URL: http://hdl.handle.net/10113/17941
Citation: Sainju, U.M., Senwo, Z.N., Nyakatawa, E.Z., Tazisong, I.A., Reddy, C. 2008. Tillage, cropping systems,and nitrogen fertilizer source effects on soil carbon sequestration and fractions. Journal of Environmental Quality. 37:880-888.

Interpretive Summary: Management practices, such as tillage, cover cropping, and N fertilization either from inorganic fertilizers or from poultry manure can influence soil C sequestration and carbon fractions. Information on the effects of management practices on C sequestration is needed for C trading and greenhouse gas mitigation and on C fractions to improve biological soil quality. Although soil organic carbon is a key component of soil quality and productivity, its measurement alone does not adequately reflect changes in soil quality and nutrient status. This is because SOC has large pool size and inherent spatial variability. Measurement of biologically active fractions of soil organic C could better reflect changes in soil quality and productivity that alter nutrient dynamics due to immobilization-mineralization. Poultry manure, an inexpensive source of nutrients widely available in the southeastern USA, can be used to sequester soil C and improve soil quality. We evaluated the 10-yr effect of combinations of tillage (no-tillage, mulch tillage, and conventional tillage), cover crop (rye vs. none), and N fertilization source and rate (0 and 100 kg N ha-1 from NH4NO3 and 100 and 200 kg N ha-1 from poultry manure) on the amount of crop residues returned to the soil and soil organic C (SOC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM) at the 0 to 20 cm depth. The SOC is considered as slow C fraction, POC as intermediate fraction, and MBC and PCM as active fractions. A field experiment was conducted from 1996 to 2005 on Decatur silt loam in northern Alabama. The amount of crop residue returned to the soil increased with N fertilization from NH4NO3 and poultry manure, regardless of tillage or cover crop. While soil C fractions were not influenced by treatments at 10 to 20 cm, SOC and POC concentrations at 0 to 10 cm were 21 to 66% greater in rye cover cropping and N fertilization with or without tillage than in no rye and N fertilization with conventional tillage. Similarly, with or without tillage, PCM and MBC were 19 to 46% greater in poultry manure with rye than in 0 and 100 kg N ha-1 from NH4NO3 with or without rye. To a depth of 20 cm, SOC, POC, and PCM contents were 14 to 44% greater in rye with poultry manure than in no rye with 0 and 100 kg N ha-1, regardless of tillage. The 100 kg N ha-1 increased SOC compared with 0 kg N ha-1 and poultry manure increased SOC, PCM, and MBC compared with 0 and 100 kg N ha-1. Tillage had minimum impact on soil C fractions compared with cover cropping and N fertilization. In contrast, poultry manure had overriding effect on soil C sequestration, with a rate of 690 kg C ha-1 yr-1, and soil C fractions because of increased C inputs both from manure and crop biomass. Long-term N fertilization from inorganic N fertilizer or poultry manure with rye cover cropping increased C sequestration and microbial biomass and activities compared with conventional tillage with no cover cropping and N fertilization, indicating improved soil quality.

Technical Abstract: Quantification of soil C cycling as influenced by management practices is needed for C sequestration, greenhouse gas mitigation, soil quality improvement, and crop production. We evaluated the 10-yr effect of combinations of tillage (no-tillage, mulch tillage, and conventional tillage), cover crop [rye (Secale cereale L.) vs. none], and N fertilization source and rate (0 and 100 kg N ha-1 from NH4NO3 and 100 and 200 kg N ha-1 from poultry manure) on crop residues and soil organic C (SOC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM) at the 0 to 20 cm depth. A field experiment was conducted from 1996 to 2005 on Decatur silt loam (clayey, kaolinitic, thermic, Typic Paleudults) in northern Alabama. The amount of crop residue returned to the soil increased with N fertilization from NH4NO3 and poultry manure, regardless of tillage or cover crop. While soil C fractions were not influenced by treatments at 10 to 20 cm, SOC and POC concentrations at 0 to 10 cm were 21 to 66% greater in rye cover cropping and N fertilization with or without tillage than in no rye and N fertilization with conventional tillage. Similarly, with or without tillage, PCM and MBC were 19 to 46% greater in poultry manure with rye than in 0 and 100 kg N ha-1 from NH4NO3 with or without rye. To a depth of 20 cm, SOC, POC, and PCM contents were 14 to 44% greater in rye with poultry manure than in no rye with 0 and 100 kg N ha-1, regardless of tillage. The 100 kg N ha-1 increased SOC compared with 0 kg N ha-1 and poultry manure increased SOC, PCM, and MBC compared with 0 and 100 kg N ha-1. While tillage had minimum impact on soil C fractions, long-term N fertilization from inorganic N fertilizer or poultry manure with rye cover cropping increased C sequestration and microbial biomass and activities, indicating improved soil quality.

Last Modified: 10/22/2014
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