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.