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ARS Home » Plains Area » Sidney, Montana » Northern Plains Agricultural Research Laboratory » Agricultural Systems Research » Research » Publications at this Location » Publication #205895
Title: Long-term tillage frequency and cropping intensity effects on dryland residue and soil carbon fractions

Author
item Sainju, Upendra
item Caesar, Thecan
item Lenssen, Andrew
item Evans, Robert
item Kolberg, Robert

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2007
Publication Date: 10/1/2007
Citation: Sainju, U.M., Caesar, T., Lenssen, A.W., Evans, R.G., Kolberg, R.L. 2007. Long-term tillage frequency and cropping intensity effects on dryland residue and soil carbon fractions. Soil Science Society of America Journal. 71(6):1730-1739.

Interpretive Summary: Maintaining soil organic matter levels in drylands of the northern Great Plains is needed not only to increase C sequestration for C trading and mitigate greenhouse gases, such as CO2, but also to improve soil quality for increasing crop production. An increase in soil organic C content of 0.58 Mg ha-1 in the surface 3 cm of soil can increase wheat grain yield by 15.6 kg ha-1 due to enhanced soil structure and improved soil water-nutrient-crop productivity relationships. The enhanced soil aggregation and crop residue C can also reduce soil erosion, especially in semi-arid regions where soil erosion due to action of wind is greater than in humid regions. The 21-yr effects of combinations of three tillage frequencies and three cropping systems were evaluated on dryland crop biomass returned to the soil, residue C, and soil C fractions at the 0 to 20 cm depth in eastern Montana. Tillage frequencies were no-till (NT), spring till (ST), and fall and spring till (FST) and cropping systems were continuous spring wheat (CW), spring wheat-barley (1984-1999) followed by spring wheat-pea (2000-2004) (W-B/P), and spring wheat-fallow (W-F). Carbon fractions were soil organic C (SOC), soil inorganic C (SIC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM). Mean annualized crop biomass was greater in NTCW, STCW, FSTCW, and FSTW-B/P than in STW-F. Soil surface residue amount and C content in 2004 were greater in NTCW and FSTCW than in STW-F. As a result, soil C fractions at 0 to 20 cm were also greater in all other treatments than in STW-F due to increased C input. At 0 to 5 cm, SOC, SIC, POC, and PCM were greater in NTCW than in FSTW-B/P. At 5 to 20 cm, POC was greater in NTCW than in FSTW-B/P and PCM was greater in STCW than in FSTCW. Reduced tillage with continuous cropping increased dryland crop biomass, residue C, and soil C fractions compared with the conventional system, such as STW-F, after 21 yr, thereby increasing soil C sequestration and biological soil quality in the northern Great Plains. The NTCW and STCW sequestered C at 214 kg C ha-1 yr-1 while STW-F lost C at 186 kg C ha-1 yr-1. Increase in tillage frequency, followed by replacement of CW by W-B/P in the continuous cropping system, however, reduced soil C fractions.

Technical Abstract: Long-term soil and crop management practices are needed to increase dryland C sequestration for C trading and C fractions to improve soil quality. We evaluated the 21-yr effects of combinations of three tillage frequencies and three cropping systems on dryland crop biomass returned to the soil, residue C, and soil C fractions at the 0 to 20 cm depth. Tillage frequencies were no-till (NT), spring till (ST), and fall and spring till (FST) and cropping systems were continuous spring wheat (Triticum aestivum L.) (CW), spring wheat-barley (Hordeum vulgare L) (1984-1999) followed by spring wheat-pea (Pisum sativum L.) (2000-2004) (W-B/P), and spring wheat-fallow (W-F). Carbon fractions were soil organic C (SOC), soil inorganic C (SIC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM). A field experiment was conducted from 1984 to 2004 in Dooley sandy loam (fine-loamy, mixed, frigid, Typic Argiboroll) in eastern Montana. Mean annualized crop biomass was 53 to 66% greater in NTCW, STCW, FSTCW, and FSTW-B/P than in STW-F. Soil surface residue amount and C content in 2004 were 46 to 60% greater in NTCW and FSTCW than in STW-F. As a result, soil C fractions at 0 to 20 cm were 23 to 141% greater in all other treatments than in STW-F due to increased C input. At 0 to 5 cm, SOC, SIC, POC, and PCM were greater in NTCW than in FSTW-B/P. At 5 to 20 cm, POC was greater in NTCW than in FSTW-B/P and PCM was greater in STCW than in FSTCW. Reduced tillage with continuous cropping increased dryland crop biomass, residue C, and soil C fractions compared with the conventional system, such as STW-F, after 21 yr, thereby increasing soil C sequestration and biological soil quality. Increase in tillage frequency, followed by replacement of CW by W-B/P in the continuous cropping system, however, reduced soil C fractions.