A long-term study was conducted at 2 sites in E. Colorado to study the influence of N fertilizer rate and source/placement/timing (NSP), and crop rotation wheat/fallow (WF), and wheat, maize or sorghum/fallow (MSF) on no-tillage dryland cropping systems. Grain yield and vegetative biomass increased linearly with fertilizer N rate up to 84 kg/ha for wheat and 101 kg/ha for maize indicating that current N recommendations at Colorado State University may be insufficient for meeting N needs of no-tillage crops. N fertilizer recovery efficiency (NFRE) decreased with N fertilizer rate. Production increased more with N fertilizer additions in the MSF than in the WF rotation system. If differences occurred with NSP treatments, banding gave greater production and NFRE than broadcast application. In 1989 at one location, wheat production from the MSF rotation was greater than from the WF rotation. The av. annual grain and vegetative production from MSF was approx. double that produced in the WF cropping system. Water conservation with no-tillage systems allowed more intense cropping than a WF rotation. N loss from the MSF rotation was significant, increased with N rate and was attributed to N loss in both inorganic- and organic-N pools. Nitrate leaching in the no-tillage MSF rotation was unlikely since NO 3 decreased with soil depth.
