Monitoring the N release from organic amendments using proximal sensing

Daniele De Rosa1, David W. Rowlings1, Johannes Biala1, Clemens Scheer1, Bruno Basso2, Massimiliano De Antoni Migliorati1, Peter Grace1

1Institute for Future Environments, Queensland University of Technology, Brisbane, QLD 4000, Australia

2Department of Geological Sciences and W.K. Kellogg Biological Station, Michigan State University, East Lansing, MI 48823, USA


The use of proximal sensed vegetation indices can reduce the uncertainty linked to the N supplied by organic amendments in a horticultural field by detecting in-season crop N status. This research assessed the applicability of the three vegetation indices (VI) of NDVI, NDRE and CCCI to evaluate the in-season long term optimized strategy of applying organic amendments to a horticultural crop (lettuce) over two seasons. A conventional urea application rate (CONV) was compared with raw (Ma) feedlot manure and Ma combined with standard (Ma+CONV) and optimized urea rate (Ma+Op). NDRE most accurately predicted crop N status at the late stage of lettuce development with an R2 of 0.67 (RMSE 0.61), compared to 0.60 (RMSE 0.67) and 0.62 (RMSE 0.66) for NDVI and CCCI respectively. The in-season acquisition of crop reflectance proved to be a valid technique to determine the efficiency of an optimized combination between organic amendments and N-fertilizer.