Eight Years of Tillage, Crop Rotation, and Cultural Practice Impact on Soil Carbon and Nitrogen.

Information on the long-term effect of management practices on soil C and N stocks is lacking. An experiment was conducted from 2004 to 2011 in the northern Great Plains, USA to examine the effects of tillage, crop rotation, and cultural practice on crop biomass (stems + leaves) and grain yields and soil total C (STC) and total N (STN) stocks at the 0-120 cm depth. Tillage practices were no-tillage (NT) and conventional tillage (CT), crop rotations were continuous spring wheat (Triticum aestivum L.) (CW), spring wheat-pea (Pisum sativum L.) (W-P), spring wheat-barley (Hordeum vulgaris L.) hay-pea (W-B-P), and spring wheat-barley hay-corn (Zea mays L.)-pea (W-B-C-P)], and cultural practices were traditional (conventional seed rates and plant spacing, conventional planting date, broadcast N fertilization, and reduced stubble height) and improved (variable seed rates and plant spacing, delayed planting, banded N fertilization, and increased stubble height). Crop biomass and grain yields were greater with W-B-C-P than other crop rotations and grain yield greater with the traditional than the improved practice. The STC at 10-20 cm and 90-120 cm was greater with CW or W-P than other crop rotations with CT and greater with CW than W-B-P with NT. The STN at 20-40 cm was greater with W-P than CW and W-B-P with CT. With NT and the improved practice, STN at 0-5, 5-10, 20-40, and 60-90 cm was greater with W-P and W-B-C-P than other crop rotations. Crop yields increased with W-B-C-P, but STC and STN decreased with W-B-P, especially with NT and the improved practice. Removal of aboveground crop biomass for hay decreased soil C and N stocks in W-B-P.