Abstract
Abstract Nitrogen (N) is one of the essential nutrients for plant growth, and its availability and spatial distribution in dryland need to be known for better soil and crop management. However, mapping soil N content is expensive and time consuming. The aim of this research is to test the use of soil spectral reflectance to rapidly measure and map soil total N in North Lombok dryland. About 300 soil samples, including the coordinates, were collected in Kayangan Sub-district of North Lombok, Indonesia. The samples were dried, ground, sieved (0.2 mm diameter), which then analysed for total N content using Kjeldhal method, and scanned using near infrared spectroscopy (NIRS). A calibration model was developed using partial least square regression (PLSR) from Kjeldhal-analysed N data and soil spectral data. The model was then used to predict the soil N content from the spectral data, and then soil nitrogen content was spatially mapped. The result showed that soil spectral reflectance technology was able to measure and map total N distribution in soil although the range of soil N content was from very low to medium. This shows that the technology can be used to map soil N distribution in dryland North Lombok, which may then be used for the guidance of fertiliser application.