Precision Manure Management across Site-Specific Management Zones: Grain Yield and Economic Analysis

Precision manure management is a relatively new concept that merges the best agronomic and manure management practices along with precision agricultural techniques, such as site-specific management zones (MZs), for agricultural productivity and environmental quality. The objective of the study was to assess the influence and compare the economic efficiency of variable-rate applications of animal manure on grain yield in maize (Zea mays L.) fields across MZs in limited irrigation cropping systems. The study was conducted on furrow-irrigated maize fields in northeastern Colorado, USA. Fields were classified into low, medium, and high yielding MZs, based on soil color, elevation, and yield history. Experimental strips were 4.5 m wide and 540 m long spanning across all MZs with manure and N fertilizer management strategies nested within MZs. Variable-rate manure applications of 22, 44, and 67 Mg ha(-1) were considered for variable yield goal (VYG) and constant yield goal (CYG) manure management strategies. The results of this study indicates that maize grain yield was significantly different across MZs a majority of times, however, not always consistent with the MZ productivity level. For instance, the low MZ showed a significantly (P <= 0.05) higher grain yield under a CYG manure management strategy. The enterprise budget analysis indicated that application of animal manure alone was economically inefficient for maize grain production. The study suggests that variable-rates of manure can be used in conjunction with synthetic N fertilizer to ensure that crop N requirements are met at early growth stages of maize.