Evaluating a Crop Circle active canopy sensor-based precision nitrogen management strategy for rice in Northeast China

It has been widely reported that active crop canopy sensor-based precision nitrogen (N) management strategy can improve N use efficiency and reduce possibilities of environmental pollution simultaneously. The two-band GreenSeeker sensor is commonly used in such strategies. However, GreenSeeker-based normalized difference vegetation index (NDVI) can become saturated at moderate to high biomass conditions. The Crop Circle ACS-470 active canopy sensor is a three-band user-configurable sensor with a choice of six spectral bands. Little research has been carried out to compare the results of precision nitrogen management strategies based on these two active canopy sensors for rice. The objective of this research was to evaluate Crop Circle ACS-470 sensor-based precision N management strategy for rice yield and N use efficiency in Northeast China. Two field experiments were conducted in 2014 in Jiansanjiang, Heilongjiang Province, China, using a randomized complete block design with four treatments and three replications. Each experiment had the same three treatments: The Regional Optimum N Management (RONM), GreenSeeker-based Precision N Management (GS-PNM) and Crop Circle-based Precision N Management (CC-PNM). The difference was that Experiment 1 used an 11 leave variety (Longjing31) and Experiment 2 used a 12-leaf variety (Longjing21). The results indicated that CC-PNM increased grain yield, N agronomic efficiency (AE_N), N partial factor productivity (PFP_N) in Experiment 2 by 18%, 46% and 20% over GreenSeeker-based precision N management (GS-PNM), respectively, which was similar to RONM. However, in Experiment 1, there was no significant difference among the three N management strategies. More studies are needed to further improve and more systematically evaluate these precision N management strategies under different on-farm conditions.