/AnMtgsAbsts2009.51788 Long-Term Tillage and Cropping Sequence Effect On Dryland Crop Yields and Carbon and Nitrogen Cycling.

Tuesday, November 3, 2009: 1:00 PM
Convention Center, Room 410, Fourth Floor

Upendra Sainju1, Andrew Lenssen1, TheCan Caesar-TonThat1, Robert Evans1 and Jalal Jabro2, (1)Northern Plains Agricultural Research Laboratory, USDA-ARS, Sidney, MT
(2)NPARL-USDA-ARS, Sidney, MT
Abstract:
Improved management practices are needed to increase dryland crop yields and soil organic matter compared with conventional farming practices in the northern Great Plains. We evaluated the 21-yr effect of tillage and cropping sequence on dryland grain and biomass (stems + leaves) yields and N uptake of spring wheat, barley, and pea and soil organic matter at the 0- to 20-cm depth in eastern Montana, USA. Treatments were no-tilled continuous spring wheat (NTCW), spring-tilled continuous spring wheat (STCW), fall- and spring-tilled continuous spring wheat (FSTCW), fall- and spring-tilled spring wheat-barley (1984-1999) followed by spring wheat-pea (2000-2004) (FSTW-B/P), and the conventional spring-tilled spring wheat-fallow (STW-F). Spring wheat grain and biomass yields and N uptake increased with crop growing season precipitation (GSP) and were greater in STW-F than in FSTCW and FSTW-B/P when GSP was <250 mm. Although mean grain and biomass yields and N uptake were greater, annualized yields and N uptake were lower in STW-F than in other treatments. In FSTW-B/P, barley and pea grain and biomass yields and N uptake increased with GSP. Soil organic C and total N were lower in STW-F than in other treatments and linearly related (R2 = 0.64 to 0.78) with total annualized biomass residue returned to the soil from 1984 to 2004. While estimated C loss through mineralization at 0- to 20-cm remained similar among treatments, estimated N loss through leaching, volatilization, or denitrification increased with increasing tillage frequency or greater with fallow than with continuous cropping. Alternate-year summer fallowing increased spring wheat grain and biomass yields, N uptake, and N loss but reduced annualized yields and soil organic matter compared with annual cropping. For sustaining dryland crop yields and soil organic matter, no-tillage with annual cropping system can be adopted in the northern Great Plains.