**5. Nutrient and water status**

Through precision farming, remote sensing and GIS can be applied to nutrient and water stress management, which are the most important fields. Utilizing remote sensing and GIS to detect nutrient stress can help us reduce cultivation costs and increase fertilizer efficiency for crops through site-specific nutrient management. Precision farming technologies can be used to judiciously use water in semi-arid and arid regions. Das and Singh [23] demonstrated that drip irrigation combined with remote sensing data can improve the efficiency of water use by reducing runoff and percolation losses. In the visible region, water stressed crops displayed higher spectral reflectance than non-stressed crops. There was a difference between stressed and non-stressed crops in terms of vegetation indices like NDVI, RVI, PVI, and GI. In the field, soil moisture can be estimated using microwave remote sensing. Through remote sensing data, it is possible to obtain information on crop water demand, water use, soil moisture conditions, and related crop growth at various stages. Sri Lankan irrigation projects were assessed using NOAA satellite data by Bandara [24], for example. In this analysis, irrigation efficiency was determined by comparing estimates from remote sensing with actual water availability. Based on high resolution land data assimilation system (HRLDAS), Das et al. [25] developed a soil moisture and temperature map for India with a spatial resolution of 1 km, in near real-time (with a few hours' latency) for four soil depths and vegetation root zones. Remote sensing has played an important role in understanding crop soil characteristics with the development of hyperspectral bands in the thermal region. Precision farming can be more effective with such information provided in conjunction with GPS. It has been demonstrated that nitrogen leaching occurs more often in wet tropical and subtropical climates due to spatial variability of soil properties, such as SOM content [26], water content [27] and yield zones [28, 29]; these properties are having a direct impact on the N nutrition status of corn plants. Bredemeier and Schmidhalter [30] indicate that this results in the overfertilization of some sites and the under fertilization of others. By using crop sensors [31, 32], we are able to increase nitrogen fertilization efficiency with variable-rate nitrogen fertilization (VRF).
