Key Points
- NIR (near infra-red) sensors use light reflectance from a range of wavelengths to calculate a number of crop indexes. The indexes correlate with parameters such as crop biomass, nitrogen content, shoot or tiller number and green leaf area.
- There are a number of NIR sensors suitable for cropping. The most common are Greenseeker, Cropcircle, Yara N sensor and Cropspec. However they all operate at different wavelengths and scales, so their outputs cannot be directly compared.
- NIR sensors can be used to estimate crop biomass, and the amount and variability of biomass can then be used to fine tune inputs such as nitrogen fertiliser. This can be done by using the NIR sensor either for crop scouting or on application equipment for real-time optimisation of inputs.
- Early experimental work in New Zealand suggests that NIR sensors have a role in predicting crop biomass and therefore nitrogen fertiliser inputs. However NIR sensors need to be used in conjunction with high accuracy GPS for maximum benefit.