Crop water and nitrogen productivity in response to long-term diversified crop rotations and management systems

Diversified crop rotation and management strategies may affect crop water and N productivity. We studied the effect of tillage, crop rotation, and management system on pre-plant and postharvest soil water storage, annualized crop yield, water use, and water and N productivity from 2005 to 2010 in the northern Great Plains, USA. Tillage were conventional tillage and no-tillage; crop rotations were continuous spring wheat (Triticum aestivum L.) (CW), spring wheat-pea (Pisum sativum L.) (WP), spring wheat-forage barley (Hordeum vulgare L.)-pea (WBP), and spring wheat-forage barley-corn (Zea mays L.)-pea (WBCP). Managements were traditional (a combination of recommended seeding rate, broadcast N fertilization, early planting, and short stubble height) and alternate (a combination of increased seeding rate, banded N fertilization, late planting, and tall stubble height) systems. Aboveground biomass was 16-85%, preplant soil water 23-118%, postharvest soil water 38-246%, and water productivity 28-61% greater with WBCP than CW in 3 out of 6 yr. Crop water use and biomass N accumulation varied with tillage, crop rotations, and management systems in various years. Grain yield was 26-41% and grain water productivity 25-32% lower with WBP than other crop rotations. Grain N accumulation was 20-52%, grain N productivity 23-60%, and grain and biomass N removal indices 18-153% greater with WP than CW and WBCP, but biomass N productivity was 98-110% lower with CW than other crop rotations. Diversified crop rotation with longer rotation length increased crop yield, soil water storage, and water productivity, but shorter rotation with legume increased grain and biomass N productivity and N removal.