Dryland Soil Carbon and Nitrogen after Thirty Years of Tillage and Cropping Sequence
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The Department of Agronomy seeks to teach the study of the farm-field, its crops, and its science and management. It originally consisted of three sub-departments to do this: Soils, Farm-Crops, and Agricultural Engineering (which became its own department in 1907). Today, the department teaches crop sciences and breeding, soil sciences, meteorology, agroecology, and biotechnology.
History
The Department of Agronomy was formed in 1902. From 1917 to 1935 it was known as the Department of Farm Crops and Soils.
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1902–present
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- Department of Farm Crops and Soils (1917–1935)
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- College of Agriculture and Life Sciences (parent college)
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Abstract
Little information is available about the long-term impact of tillage and cropping sequence on dryland soil C and N levels in the northern Great Plains. This study provided an opportunity to evaluate the effect of thirty years (1983-2013) of tillage and cropping sequence combination on dryland crop residue and soil organic (SOC) and inorganic C (SIC), soil total N (STN), NH4-N, and NO3-N contents at the 0- to 120-cm depth in eastern Montana. Treatments were no-till continuous spring wheat (NTCW), spring till continuous spring wheat (STCW), fall and spring till continuous spring wheat (FSTCW), fall and spring till spring wheat-barley (1984-1999) followed by spring wheat-pea (2000-2013) (FSTW-B/P), and spring till spring wheat-fallow (STW-F). Mean annualized crop biomass returned to the soil was lower in STW-F than in other treatments. At 0 to 7.5 cm, soil bulk density was greater in STW-F but SOC, SIC, and STN were greater in STCW than in other treatments, except NTCW, in 2013. The SIC at 90 to 120 cm was greater in NTCW and STCW than FSTCW and FSTW-B/P and STN at 30 to 60 cm was greater in NTCW and STW-F than in STCW and FSTW-B/P. The NH4-N content at 0 to 30 cm and NO3-N content at 0 to 120 cm were greater in FSTCW than in other treatments, except STCW. From 1983 to 2013, SOC at 0 to 7.5 cm declined from 104 kg C ha-1 yr-1 in STCW to 214 kg C ha-1 yr-1 in FSTW-B/P. Soil total (organic + inorganic) C was strongly related to SOC (R2 = 0.82, P ≤ 0.001, n = 168). Reduced tillage, followed by increased amount of crop residue returned to the soil, probably increased C and N storage and reduced the rate of decline in NTCW and STCW, but increased tillage intensity increased available N in FSTCW. Soil total C can be used as a substitute for SOC in dryland soils, which reduce the need to measure SICr
Comments
This poster was presented at the ASA-CSSA-SSSA Annual Meeting, Long Beach, CA, November 2-5, 2014.