Improving nitrogen use efficiency with minimal environmental risks using an active canopy sensor in a wheat-maize cropping system

Nitrogen (N) management needs to be significantly improved to address the triple challenge of global food security, environmental pollution and climate change. In addition to being site-specific, dynamic in-season management is needed to respond to temporal variability in soil N supply and crop N demand. Active canopy sensor-based precision N management (CS-PNM) aims to match N supply with crop N demand in both space and time. Studies that systematically compare this strategy with other N management strategies are limited, especially in intensively farmed regions of developing countries. The objective of this study was to compare CS-PNM strategy in terms of agronomic and environmental impacts in comparison with farmer's N practice, regional optimum N management, modified Green Window-based N Management and soil test-based in-season root zone N management for an intensive winter wheat (Triticum aestivwn L.) and summer maize (Zea mays L.) rotation system in North China Plain. A field experiment was conducted from 2008 to 2012 in Quzhou, Hebei Province of China to evaluate these systems. The CS-PNM strategy was consistently better for both crops than the other tested strategies. In comparison with farmer's practice and regional optimum N management, the CS-PNM strategy reduced N fertilizer applications by 62% and 36%, increased N use efficiencies by 68-123% and 20-61%, decreased apparent total N losses by 81% and 57%, and lowered intensities of total N2O emission, greenhouse gas emission and reactive N losses by 54-68% and 20-42%, respectively. Here we demonstrate that relative to current N management strategies, the CS-PNM strategy has significant potential to improve N use efficiencies and mitigate environmental degradation for sustainable intensification of agriculture in developing countries.