Many rice growers are now using simple Normalised Difference Vegetative Index (NDVI) images of crops to assist with crop management. These images utilize two wavelength bands – one in the visible and one in the infrared. Spectrometers/radiometers which scan visible (VIS) and NIR wavelengths are available. However, to achieve the maximum benefits from the instruments, direct comparisons on sets of crops with known density and nutrient status need to be made.
Importance of this research
This report contains the results of an evaluation of sensors which could increase the precision of variable crop fertilization. This technology could lead to higher returns per hectare and per megalitre of water through the achievement of uniformly high yields of high quality rice. The results would have immediate value to rice growers when incorporated into the SunRice Tissue Testing Service.
Objectives/aims of the proposed research
The aims of this project were to provide:
• an evaluation of the potential of available airborne scanning NIR sensors to determine variations in dry matter and shoot composition (eg Nitrogen and starch) across rice crops
• an understanding of the limitations of fresh tissue analysis by airborne NIR sensors
• calibrations for nutrients in fresh rice tissue for use in interpreting data obtained from airborne NIR sensors
• a basis on which to keep the Tissue Testing Service in line with the latest technology.
Project results:
Key findings
Preliminary calibrations on remotely sensed spectra of rice crops, with correlations of approximately 0.85, were established for % N and N_uptake.
Implications for relevant stakeholders:
The results will be of immediate value to rice growers when the preliminary calibrations produced in this project are improved and extended to include remotely sensed spectra from several more seasons and protocols established to incorporate them into the SunRice Tissue Testing Service.
Recommendations
More remotely sensed images and the related “ground truthing” need to be acquired over a range of seasons, varieties and areas to ensure strong and robust calibrations.
Implications
The future use of remotely sensing the nutrient status of rice crops will depend on the continued availability of suitable sensors, the development of timely protocols for the delivery of data and the continual improvement of calibrations.
Project partners:
Wagga Wagga Agricultural Research Institute
