Submitted to: Agronomy Society of America, Crop Science Society of America, Soil Science Society of America Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/25/2007
Publication Date: 6/17/2007
Publication URL: http://crops.confex.com/crops/2007am/techprogram/
Citation: Sainju, U.M., Caesar, T., Lenssen, A.W., Evans, R.G. 2007. Dryland residue and soil nitrogen fractions as influenced by long-term tillage and cropping sequence. Agronomy Society of America, Crop Science Society of America, Soil Science Society of America Meeting. [Online] Paper no. 205-5. p. 113. Interpretive Summary:
Technical Abstract: Nitrogen conservation is needed to reduce the rate of N fertilization, N2O (a greenhouse gas) emission, and the potential for N leaching from dryland soils in the northern Great Plains. We evaluated the 21-yr effects of 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 (2000-2004) (FSTW-B/P), and spring till spring wheat-fallow (STW-F) on crop biomass (stems + leaves) yields, residue N, and soil N fractions at the 0- to 20-cm depth in eastern Montana. Nitrogen fractions were soil total N (STN), particulate organic N (PON), microbial biomass N (MBN), potential N mineralization (PNM), NH4-N, and NO3-N contents. Mean crop biomass returned to the soil from 1984 to 2004 was 53 to 66% lower in STW-F than in other treatments. As a result, soil surface residue amount and N content in 2004 were 76 to 127% greater in other treatments than in STW-F. At 0 to 5 cm, STN and PON were greater in NTCW and STCW than in STW-F, and MBN was greater in other treatments than in STW-F. At 5 to 20 cm, STN and PON were greater in NTCW and STCW than in STW-F, PNM and MBN were greater in STCW than in NTCW and STW-F, and NO3-N was greater in FSTW-B/P than in NTCW and FSTCW. Long-term reduced tillage with continuous cropping increased dryland crop biomass, residue N, and soil N storage compared with the conventional system, such as STW-F. Increase in tillage frequency and inclusion of legumes, such as pea, in the crop rotation, however, increased N mineralization and availability at the subsurface soil.