B.  Haggard, D.C.  Weindorf, J.  Lofton, B.  Tubana, 
    Nitrogen Variability: A Need for Precision Agriculture,
    Agricultural Journal,
    Volume 5,Issue 1,
    2010,
    Pages 6-11,
    ISSN 1816-9155,
    aj.2010.6.11,
    (https://makhillpublications.co/view-article.php?doi=aj.2010.6.11)
    Abstract: Nitrogen (N) variability can have a negative impact on many production practices as well as having a negative influence on the environment. Nitrogen can be highly variable, both spatially and temporally. This is due to the N cycle being such a dynamic system. Producers have to change management practices to account for this variability. One way to manage N variability is the implementation of precision management practices. Scale of N variability is important, when implementing precision management. In some sites, the resolution of N variability is too fine to implement traditional precision agriculture management, such as management zone soil sampling, therefore remote sensing needs to be implemented. Many ground-based remote sensors are able to detect fine resolution differences however, delays between sensing and implementing management practices makes them flawed. Therefore, on-the-go sensors that indirectly measure nutrient status by plant tissue can be utilized to minimize this downtime. Many of these sensors are available, such as the Greenseeker™ and the Crop Circle™. Implementing these practices has been shown to increase the N use efficiency in crops therefore increasing potential yield and decreasing environmental hazards.
    Keywords: site-specific management;precision farming;remote sensing;precision agriculture;temporal variability;spatial variability;Nitrogen;nitrogen use efficiency;Greenseeker™;Crop Circle™